Add discussion API

* adds basic discussions API for issues and snippets * reorganizes notes specs (so same tests can be used for all noteable types - issues, MRs, snippets)

Add discussion API
* adds basic discussions API for issues and snippets * reorganizes notes specs (so same tests can be used for all noteable types - issues, MRs, snippets)
dcdfa04b · Jan Provaznik · 8a0052c0 · dcdfa04b · dcdfa04b · dcdfa04b
Commit dcdfa04b authored Feb 28, 2018 by Jan Provaznik
22 changed files
--- a/app/models/concerns/issuable.rb
+++ b/app/models/concerns/issuable.rb
@@ -222,6 +222,10 @@ module Issuable
    def to_ability_name
      model_name.singular
    end
+
+    def parent_class
+      ::Project
+    end
  end

  def today?

--- a/app/models/note.rb
+++ b/app/models/note.rb
@@ -81,7 +81,7 @@ class Note < ActiveRecord::Base
  validates :author, presence: true
  validates :discussion_id, presence: true, format: { with: /\A\h{40}\z/ }

-  validate unless: [:for_commit?, :importing?, :for_personal_snippet?] do |note|
+  validate unless: [:for_commit?, :importing?, :skip_project_check?] do |note|
    unless note.noteable.try(:project) == note.project
      errors.add(:project, 'does not match noteable project')
    end
@@ -228,7 +228,7 @@ class Note < ActiveRecord::Base
  end

  def skip_project_check?
-    for_personal_snippet?
+    !for_project_noteable?
  end

  def commit
@@ -308,6 +308,11 @@ class Note < ActiveRecord::Base
    self.noteable.supports_discussions? && !part_of_discussion?
  end

+  def can_create_todo?
+    # Skip system notes, and notes on project snippet
+    !system? && !for_snippet?
+  end
+
  def discussion_class(noteable = nil)
    # When commit notes are rendered on an MR's Discussion page, they are
    # displayed in one discussion instead of individually.

--- a/app/models/snippet.rb
+++ b/app/models/snippet.rb
@@ -168,5 +168,9 @@ class Snippet < ActiveRecord::Base
    def search_code(query)
      fuzzy_search(query, [:content])
    end
+
+    def parent_class
+      ::Project
+    end
  end
 end
--- a/app/services/notes/build_service.rb
+++ b/app/services/notes/build_service.rb
@@ -26,14 +26,19 @@ module Notes
      if project
        project.notes.find_discussion(discussion_id)
      else
-        # only PersonalSnippets can have discussions without project association
        discussion = Note.find_discussion(discussion_id)
        noteable = discussion.noteable

-        return nil unless noteable.is_a?(PersonalSnippet) && can?(current_user, :comment_personal_snippet, noteable)
+        return nil unless noteable_without_project?(noteable)

        discussion
      end
    end
+
+    def noteable_without_project?(noteable)
+      return true if noteable.is_a?(PersonalSnippet) && can?(current_user, :comment_personal_snippet, noteable)
+
+      false
+    end
  end
 end
--- a/app/services/notes/post_process_service.rb
+++ b/app/services/notes/post_process_service.rb
@@ -11,7 +11,7 @@ module Notes
      unless @note.system?
        EventCreateService.new.leave_note(@note, @note.author)

-        return if @note.for_personal_snippet?
+        return unless @note.for_project_noteable?

        @note.create_cross_references!
        execute_note_hooks

--- a/app/services/notification_recipient_service.rb
+++ b/app/services/notification_recipient_service.rb
@@ -280,7 +280,7 @@ module NotificationRecipientService
        add_participants(note.author)
        add_mentions(note.author, target: note)

-        unless note.for_personal_snippet?
+        if note.for_project_noteable?
          # Merge project watchers
          add_project_watchers


--- a/app/services/todo_service.rb
+++ b/app/services/todo_service.rb
@@ -241,8 +241,7 @@ class TodoService
  end

  def handle_note(note, author, skip_users = [])
-    # Skip system notes, and notes on project snippet
-    return if note.system? || note.for_snippet?
+    return unless note.can_create_todo?

    project = note.project
    target  = note.noteable

--- a/changelogs/unreleased/discussions-api.yml
+++ b/changelogs/unreleased/discussions-api.yml
+---
+title: Add discussions API for Issues and Snippets
+merge_request:
+author:
+type: added
--- a/doc/api/README.md
+++ b/doc/api/README.md
@@ -35,6 +35,7 @@ following locations:
 - [Group milestones](group_milestones.md)
 - [Namespaces](namespaces.md)
 - [Notes](notes.md) (comments)
+- [Threaded comments](discussions.md)
 - [Notification settings](notification_settings.md)
 - [Open source license templates](templates/licenses.md)
 - [Pages Domains](pages_domains.md)

--- a/doc/api/discussions.md
+++ b/doc/api/discussions.md
+# Discussions API
+
+Discussions are set of related notes on snippets, issues or epics.
+
+## Issues
+
+### List project issue discussions
+
+Gets a list of all discussions for a single issue.
+
+```
+GET /projects/:id/issues/:issue_iid/discussions
+```
+
+| Attribute           | Type             | Required   | Description  |
+| ------------------- | ---------------- | ---------- | ------------ |
+| `id`                | integer/string   | yes        | The ID or [URL-encoded path of the project](README.md#namespaced-path-encoding) |
+| `issue_iid`         | integer          | yes        | The IID of an issue |
+
+```json
+[
+  {
+    "id": "6a9c1750b37d513a43987b574953fceb50b03ce7",
+    "individual_note": false,
+    "notes": [
+      {
+        "id": 1126,
+        "type": "DiscussionNote",
+        "body": "discussion text",
+        "attachment": null,
+        "author": {
+          "id": 1,
+          "name": "root",
+          "username": "root",
+          "state": "active",
+          "avatar_url": "https://www.gravatar.com/avatar/00afb8fb6ab07c3ee3e9c1f38777e2f4?s=80&d=identicon",
+          "web_url": "http://localhost:3000/root"
+        },
+        "created_at": "2018-03-03T21:54:39.668Z",
+        "updated_at": "2018-03-03T21:54:39.668Z",
+        "system": false,
+        "noteable_id": 3,
+        "noteable_type": "Issue",
+        "noteable_iid": null
+      },
+      {
+        "id": 1129,
+        "type": "DiscussionNote",
+        "body": "reply to the discussion",
+        "attachment": null,
+        "author": {
+          "id": 1,
+          "name": "root",
+          "username": "root",
+          "state": "active",
+          "avatar_url": "https://www.gravatar.com/avatar/00afb8fb6ab07c3ee3e9c1f38777e2f4?s=80&d=identicon",
+          "web_url": "http://localhost:3000/root"
+        },
+        "created_at": "2018-03-04T13:38:02.127Z",
+        "updated_at": "2018-03-04T13:38:02.127Z",
+        "system": false,
+        "noteable_id": 3,
+        "noteable_type": "Issue",
+        "noteable_iid": null
+      }
+    ]
+  },
+  {
+    "id": "87805b7c09016a7058e91bdbe7b29d1f284a39e6",
+    "individual_note": true,
+    "notes": [
+      {
+        "id": 1128,
+        "type": null,
+        "body": "a single comment",
+        "attachment": null,
+        "author": {
+          "id": 1,
+          "name": "root",
+          "username": "root",
+          "state": "active",
+          "avatar_url": "https://www.gravatar.com/avatar/00afb8fb6ab07c3ee3e9c1f38777e2f4?s=80&d=identicon",
+          "web_url": "http://localhost:3000/root"
+        },
+        "created_at": "2018-03-04T09:17:22.520Z",
+        "updated_at": "2018-03-04T09:17:22.520Z",
+        "system": false,
+        "noteable_id": 3,
+        "noteable_type": "Issue",
+        "noteable_iid": null
+      }
+    ]
+  }
+]
+```
+
+```bash
+curl --request GET --header "PRIVATE-TOKEN: 9koXpg98eAheJpvBs5tK" https://gitlab.example.com/api/v4/projects/5/issues/11/discussions
+```
+
+### Get single issue discussion
+
+Returns a single discussion for a specific project issue
+
+```
+GET /projects/:id/issues/:issue_iid/discussions/:discussion_id
+```
+
+Parameters:
+
+| Attribute       | Type           | Required | Description |
+| --------------- | -------------- | -------- | ----------- |
+| `id`            | integer/string | yes      | The ID or [URL-encoded path of the project](README.md#namespaced-path-encoding) |
+| `issue_iid`     | integer        | yes      | The IID of an issue |
+| `discussion_id` | integer        | yes      | The ID of a discussion |
+
+```bash
+curl --request GET --header "PRIVATE-TOKEN: 9koXpg98eAheJpvBs5tK" https://gitlab.example.com/api/v4/projects/5/issues/11/discussions/6a9c1750b37d513a43987b574953fceb50b03ce7
+```
+
+### Create new issue discussion
+
+Creates a new discussion to a single project issue. This is similar to creating
+a note but but another comments (replies) can be added to it later.
+
+```
+POST /projects/:id/issues/:issue_iid/discussions
+```
+
+Parameters:
+
+| Attribute       | Type           | Required | Description |
+| --------------- | -------------- | -------- | ----------- |
+| `id`            | integer/string | yes      | The ID or [URL-encoded path of the project](README.md#namespaced-path-encoding) |
+| `issue_iid`     | integer        | yes      | The IID of an issue |
+| `body`          | string         | yes      | The content of a discussion |
+| `created_at`    | string         | no       | Date time string, ISO 8601 formatted, e.g. 2016-03-11T03:45:40Z |
+
+```bash
+curl --request POST --header "PRIVATE-TOKEN: 9koXpg98eAheJpvBs5tK" https://gitlab.example.com/api/v4/projects/5/issues/11/discussions?body=comment
+```
+
+### Add note to existing issue discussion
+
+Adds a new note to the discussion.
+
+```
+POST /projects/:id/issues/:issue_iid/discussions/:discussion_id/notes
+```
+
+Parameters:
+
+| Attribute       | Type           | Required | Description |
+| --------------- | -------------- | -------- | ----------- |
+| `id`            | integer/string | yes      | The ID or [URL-encoded path of the project](README.md#namespaced-path-encoding) |
+| `issue_iid`     | integer        | yes      | The IID of an issue |
+| `discussion_id` | integer        | yes      | The ID of a discussion |
+| `note_id`       | integer        | yes      | The ID of a discussion note |
+| `body`          | string         | yes      | The content of a discussion |
+| `created_at`    | string         | no       | Date time string, ISO 8601 formatted, e.g. 2016-03-11T03:45:40Z |
+
+```bash
+curl --request POST --header "PRIVATE-TOKEN: 9koXpg98eAheJpvBs5tK" https://gitlab.example.com/api/v4/projects/5/issues/11/discussions/6a9c1750b37d513a43987b574953fceb50b03ce7/notes?body=comment
+```
+
+### Modify existing issue discussion note
+
+Modify existing discussion note of an issue.
+
+```
+PUT /projects/:id/issues/:issue_iid/discussions/:discussion_id/notes/:note_id
+```
+
+Parameters:
+
+| Attribute       | Type           | Required | Description |
+| --------------- | -------------- | -------- | ----------- |
+| `id`            | integer/string | yes      | The ID or [URL-encoded path of the project](README.md#namespaced-path-encoding) |
+| `issue_iid`     | integer        | yes      | The IID of an issue |
+| `discussion_id` | integer        | yes      | The ID of a discussion |
+| `note_id`       | integer        | yes      | The ID of a discussion note |
+| `body`          | string         | yes      | The content of a discussion |
+
+```bash
+curl --request PUT --header "PRIVATE-TOKEN: 9koXpg98eAheJpvBs5tK" https://gitlab.example.com/api/v4/projects/5/issues/11/discussions/6a9c1750b37d513a43987b574953fceb50b03ce7/notes/1108?body=comment
+```
+
+### Delete an issue discussion note
+
+Deletes an existing discussion note of an issue.
+
+```
+DELETE /projects/:id/issues/:issue_iid/discussions/:discussion_id/notes/:note_id
+```
+
+Parameters:
+
+| Attribute       | Type           | Required | Description |
+| --------------- | -------------- | -------- | ----------- |
+| `id`            | integer/string | yes      | The ID or [URL-encoded path of the project](README.md#namespaced-path-encoding) |
+| `issue_iid`     | integer        | yes      | The IID of an issue |
+| `discussion_id` | integer        | yes      | The ID of a discussion |
+| `note_id`       | integer        | yes      | The ID of a discussion note |
+
+```bash
+curl --request DELETE --header "PRIVATE-TOKEN: 9koXpg98eAheJpvBs5tK" https://gitlab.example.com/api/v4/projects/5/issues/11/discussions/636
+```
+
+## Snippets
+
+### List project snippet discussions
+
+Gets a list of all discussions for a single snippet.
+
+```
+GET /projects/:id/snippets/:snippet_id/discussions
+```
+
+| Attribute           | Type             | Required   | Description |
+| ------------------- | ---------------- | ---------- | ------------|
+| `id`                | integer/string   | yes        | The ID or [URL-encoded path of the project](README.md#namespaced-path-encoding) |
+| `snippet_id`        | integer          | yes        | The ID of an snippet |
+
+```json
+[
+  {
+    "id": "6a9c1750b37d513a43987b574953fceb50b03ce7",
+    "individual_note": false,
+    "notes": [
+      {
+        "id": 1126,
+        "type": "DiscussionNote",
+        "body": "discussion text",
+        "attachment": null,
+        "author": {
+          "id": 1,
+          "name": "root",
+          "username": "root",
+          "state": "active",
+          "avatar_url": "https://www.gravatar.com/avatar/00afb8fb6ab07c3ee3e9c1f38777e2f4?s=80&d=identicon",
+          "web_url": "http://localhost:3000/root"
+        },
+        "created_at": "2018-03-03T21:54:39.668Z",
+        "updated_at": "2018-03-03T21:54:39.668Z",
+        "system": false,
+        "noteable_id": 3,
+        "noteable_type": "Snippet",
+        "noteable_id": null
+      },
+      {
+        "id": 1129,
+        "type": "DiscussionNote",
+        "body": "reply to the discussion",
+        "attachment": null,
+        "author": {
+          "id": 1,
+          "name": "root",
+          "username": "root",
+          "state": "active",
+          "avatar_url": "https://www.gravatar.com/avatar/00afb8fb6ab07c3ee3e9c1f38777e2f4?s=80&d=identicon",
+          "web_url": "http://localhost:3000/root"
+        },
+        "created_at": "2018-03-04T13:38:02.127Z",
+        "updated_at": "2018-03-04T13:38:02.127Z",
+        "system": false,
+        "noteable_id": 3,
+        "noteable_type": "Snippet",
+        "noteable_id": null
+      }
+    ]
+  },
+  {
+    "id": "87805b7c09016a7058e91bdbe7b29d1f284a39e6",
+    "individual_note": true,
+    "notes": [
+      {
+        "id": 1128,
+        "type": null,
+        "body": "a single comment",
+        "attachment": null,
+        "author": {
+          "id": 1,
+          "name": "root",
+          "username": "root",
+          "state": "active",
+          "avatar_url": "https://www.gravatar.com/avatar/00afb8fb6ab07c3ee3e9c1f38777e2f4?s=80&d=identicon",
+          "web_url": "http://localhost:3000/root"
+        },
+        "created_at": "2018-03-04T09:17:22.520Z",
+        "updated_at": "2018-03-04T09:17:22.520Z",
+        "system": false,
+        "noteable_id": 3,
+        "noteable_type": "Snippet",
+        "noteable_id": null
+      }
+    ]
+  }
+]
+```
+
+```bash
+curl --request GET --header "PRIVATE-TOKEN: 9koXpg98eAheJpvBs5tK" https://gitlab.example.com/api/v4/projects/5/snippets/11/discussions
+```
+
+### Get single snippet discussion
+
+Returns a single discussion for a specific project snippet
+
+```
+GET /projects/:id/snippets/:snippet_id/discussions/:discussion_id
+```
+
+Parameters:
+
+| Attribute       | Type           | Required | Description |
+| --------------- | -------------- | -------- | ----------- |
+| `id`            | integer/string | yes      | The ID or [URL-encoded path of the project](README.md#namespaced-path-encoding) |
+| `snippet_id`    | integer        | yes      | The ID of an snippet |
+| `discussion_id` | integer        | yes      | The ID of a discussion |
+
+```bash
+curl --request POST --header "PRIVATE-TOKEN: 9koXpg98eAheJpvBs5tK" https://gitlab.example.com/api/v4/projects/5/snippets/11/discussions/6a9c1750b37d513a43987b574953fceb50b03ce7
+```
+
+### Create new snippet discussion
+
+Creates a new discussion to a single project snippet. This is similar to creating
+a note but but another comments (replies) can be added to it later.
+
+```
+POST /projects/:id/snippets/:snippet_id/discussions
+```
+
+Parameters:
+
+| Attribute       | Type           | Required | Description |
+| --------------- | -------------- | -------- | ----------- |
+| `id`            | integer/string | yes      | The ID or [URL-encoded path of the project](README.md#namespaced-path-encoding) |
+| `snippet_id`    | integer        | yes      | The ID of an snippet |
+| `body`          | string         | yes      | The content of a discussion |
+| `created_at`    | string         | no       | Date time string, ISO 8601 formatted, e.g. 2016-03-11T03:45:40Z |
+
+```bash
+curl --request POST --header "PRIVATE-TOKEN: 9koXpg98eAheJpvBs5tK" https://gitlab.example.com/api/v4/projects/5/snippets/11/discussions?body=comment
+```
+
+### Add note to existing snippet discussion
+
+Adds a new note to the discussion.
+
+```
+POST /projects/:id/snippets/:snippet_id/discussions/:discussion_id/notes
+```
+
+Parameters:
+
+| Attribute       | Type           | Required | Description |
+| --------------- | -------------- | -------- | ----------- |
+| `id`            | integer/string | yes      | The ID or [URL-encoded path of the project](README.md#namespaced-path-encoding) |
+| `snippet_id`    | integer        | yes      | The ID of an snippet |
+| `discussion_id` | integer        | yes      | The ID of a discussion |
+| `note_id`       | integer        | yes      | The ID of a discussion note |
+| `body`          | string         | yes      | The content of a discussion |
+| `created_at`    | string         | no       | Date time string, ISO 8601 formatted, e.g. 2016-03-11T03:45:40Z |
+
+```bash
+curl --request POST --header "PRIVATE-TOKEN: 9koXpg98eAheJpvBs5tK" https://gitlab.example.com/api/v4/projects/5/snippets/11/discussions/6a9c1750b37d513a43987b574953fceb50b03ce7/notes?body=comment
+```
+
+### Modify existing snippet discussion note
+
+Modify existing discussion note of an snippet.
+
+```
+PUT /projects/:id/snippets/:snippet_id/discussions/:discussion_id/notes/:note_id
+```
+
+Parameters:
+
+| Attribute       | Type           | Required | Description |
+| --------------- | -------------- | -------- | ----------- |
+| `id`            | integer/string | yes      | The ID or [URL-encoded path of the project](README.md#namespaced-path-encoding) |
+| `snippet_id`    | integer        | yes      | The ID of an snippet |
+| `discussion_id` | integer        | yes      | The ID of a discussion |
+| `note_id`       | integer        | yes      | The ID of a discussion note |
+| `body`          | string         | yes      | The content of a discussion |
+
+```bash
+curl --request PUT --header "PRIVATE-TOKEN: 9koXpg98eAheJpvBs5tK" https://gitlab.example.com/api/v4/projects/5/snippets/11/discussions/6a9c1750b37d513a43987b574953fceb50b03ce7/notes/1108?body=comment
+```
+
+### Delete an snippet discussion note
+
+Deletes an existing discussion note of an snippet.
+
+```
+DELETE /projects/:id/snippets/:snippet_id/discussions/:discussion_id/notes/:note_id
+```
+
+Parameters:
+
+| Attribute       | Type           | Required | Description |
+| --------------- | -------------- | -------- | ----------- |
+| `id`            | integer/string | yes      | The ID or [URL-encoded path of the project](README.md#namespaced-path-encoding) |
+| `snippet_id`    | integer        | yes      | The ID of an snippet |
+| `discussion_id` | integer        | yes      | The ID of a discussion |
+| `note_id`       | integer        | yes      | The ID of a discussion note |
+
+```bash
+curl --request DELETE --header "PRIVATE-TOKEN: 9koXpg98eAheJpvBs5tK" https://gitlab.example.com/api/v4/projects/5/snippets/11/discussions/636
+```
--- a/doc/api/notes.md
+++ b/doc/api/notes.md
@@ -15,7 +15,7 @@ GET /projects/:id/issues/:issue_iid/notes?sort=asc&order_by=updated_at

 | Attribute           | Type             | Required   | Description                                                                                                                                         |
 | ------------------- | ---------------- | ---------- | --------------------------------------------------------------------------------------------------------------------------------------------------- |
-| `id`                | integer/string   | yes        | The ID or [URL-encoded path of the project](README.md#namespaced-path-encoding) owned by the authenticated user
+| `id`                | integer/string   | yes        | The ID or [URL-encoded path of the project](README.md#namespaced-path-encoding)
 | `issue_iid`         | integer          | yes        | The IID of an issue
 | `sort`              | string           | no         | Return issue notes sorted in `asc` or `desc` order. Default is `desc`
 | `order_by`          | string           | no         | Return issue notes ordered by `created_at` or `updated_at` fields. Default is `created_at`
@@ -63,6 +63,10 @@ GET /projects/:id/issues/:issue_iid/notes?sort=asc&order_by=updated_at
 ]
 ```

+```bash
+curl --request GET --header "PRIVATE-TOKEN: 9koXpg98eAheJpvBs5tK" https://gitlab.example.com/api/v4/projects/5/issues/11/notes
+```
+
 ### Get single issue note

 Returns a single note for a specific project issue
@@ -73,14 +77,17 @@ GET /projects/:id/issues/:issue_iid/notes/:note_id

 Parameters:

- `id` (required) - The ID or [URL-encoded path of the project](README.md#namespaced-path-encoding) owned by the authenticated user
+- `id` (required) - The ID or [URL-encoded path of the project](README.md#namespaced-path-encoding)
 - `issue_iid` (required) - The IID of a project issue
 - `note_id` (required) - The ID of an issue note

+```bash
+curl --request GET --header "PRIVATE-TOKEN: 9koXpg98eAheJpvBs5tK" https://gitlab.example.com/api/v4/projects/5/issues/11/notes/1
+```
+
 ### Create new issue note

-Creates a new note to a single project issue. If you create a note where the body
-only contains an Award Emoji, you'll receive this object back.
+Creates a new note to a single project issue.

 ```
 POST /projects/:id/issues/:issue_iid/notes
@@ -88,11 +95,15 @@ POST /projects/:id/issues/:issue_iid/notes

 Parameters:

- `id` (required) - The ID or [URL-encoded path of the project](README.md#namespaced-path-encoding) owned by the authenticated user
+- `id` (required) - The ID or [URL-encoded path of the project](README.md#namespaced-path-encoding)
 - `issue_id` (required) - The IID of an issue
 - `body` (required) - The content of a note
 - `created_at` (optional) - Date time string, ISO 8601 formatted, e.g. 2016-03-11T03:45:40Z

+```bash
+curl --request POST --header "PRIVATE-TOKEN: 9koXpg98eAheJpvBs5tK" https://gitlab.example.com/api/v4/projects/5/issues/11/notes?body=note
+```
+
 ### Modify existing issue note

 Modify existing note of an issue.
@@ -103,11 +114,15 @@ PUT /projects/:id/issues/:issue_iid/notes/:note_id

 Parameters:

- `id` (required) - The ID or [URL-encoded path of the project](README.md#namespaced-path-encoding) owned by the authenticated user
+- `id` (required) - The ID or [URL-encoded path of the project](README.md#namespaced-path-encoding)
 - `issue_iid` (required) - The IID of an issue
 - `note_id` (required) - The ID of a note
 - `body` (required) - The content of a note

+```bash
+curl --request PUT --header "PRIVATE-TOKEN: 9koXpg98eAheJpvBs5tK" https://gitlab.example.com/api/v4/projects/5/issues/11/notes?body=note
+```
+
 ### Delete an issue note

 Deletes an existing note of an issue.
@@ -120,7 +135,7 @@ Parameters:

 | Attribute | Type | Required | Description |
 | --------- | ---- | -------- | ----------- |
-| `id` | integer/string | yes | The ID or [URL-encoded path of the project](README.md#namespaced-path-encoding) owned by the authenticated user |
+| `id` | integer/string | yes | The ID or [URL-encoded path of the project](README.md#namespaced-path-encoding) |
 | `issue_iid` | integer | yes | The IID of an issue |
 | `note_id` | integer | yes | The ID of a note |

@@ -141,11 +156,15 @@ GET /projects/:id/snippets/:snippet_id/notes?sort=asc&order_by=updated_at

 | Attribute           | Type             | Required   | Description                                                                                                                                         |
 | ------------------- | ---------------- | ---------- | --------------------------------------------------------------------------------------------------------------------------------------------------- |
-| `id`                | integer/string   | yes        | The ID or [URL-encoded path of the project](README.md#namespaced-path-encoding) owned by the authenticated user
+| `id`                | integer/string   | yes        | The ID or [URL-encoded path of the project](README.md#namespaced-path-encoding)
 | `snippet_id`        | integer          | yes        | The ID of a project snippet
 | `sort`              | string           | no         | Return snippet notes sorted in `asc` or `desc` order. Default is `desc`
 | `order_by`          | string           | no         | Return snippet notes ordered by `created_at` or `updated_at` fields. Default is `created_at`

+```bash
+curl --request GET --header "PRIVATE-TOKEN: 9koXpg98eAheJpvBs5tK" https://gitlab.example.com/api/v4/projects/5/snippets/11/notes
+```
+
 ### Get single snippet note

 Returns a single note for a given snippet.
@@ -156,7 +175,7 @@ GET /projects/:id/snippets/:snippet_id/notes/:note_id

 Parameters:

- `id` (required) - The ID or [URL-encoded path of the project](README.md#namespaced-path-encoding) owned by the authenticated user
+- `id` (required) - The ID or [URL-encoded path of the project](README.md#namespaced-path-encoding)
 - `snippet_id` (required) - The ID of a project snippet
 - `note_id` (required) - The ID of a snippet note

@@ -179,6 +198,10 @@ Parameters:
 }
 ```

+```bash
+curl --request GET --header "PRIVATE-TOKEN: 9koXpg98eAheJpvBs5tK" https://gitlab.example.com/api/v4/projects/5/snippets/11/notes/11
+```
+
 ### Create new snippet note

 Creates a new note for a single snippet. Snippet notes are comments users can post to a snippet.
@@ -190,10 +213,14 @@ POST /projects/:id/snippets/:snippet_id/notes

 Parameters:

- `id` (required) - The ID or [URL-encoded path of the project](README.md#namespaced-path-encoding) owned by the authenticated user
+- `id` (required) - The ID or [URL-encoded path of the project](README.md#namespaced-path-encoding)
 - `snippet_id` (required) - The ID of a snippet
 - `body` (required) - The content of a note

+```bash
+curl --request POST --header "PRIVATE-TOKEN: 9koXpg98eAheJpvBs5tK" https://gitlab.example.com/api/v4/projects/5/snippet/11/notes?body=note
+```
+
 ### Modify existing snippet note

 Modify existing note of a snippet.
@@ -204,11 +231,15 @@ PUT /projects/:id/snippets/:snippet_id/notes/:note_id

 Parameters:

- `id` (required) - The ID or [URL-encoded path of the project](README.md#namespaced-path-encoding) owned by the authenticated user
+- `id` (required) - The ID or [URL-encoded path of the project](README.md#namespaced-path-encoding)
 - `snippet_id` (required) - The ID of a snippet
 - `note_id` (required) - The ID of a note
 - `body` (required) - The content of a note

+```bash
+curl --request PUT --header "PRIVATE-TOKEN: 9koXpg98eAheJpvBs5tK" https://gitlab.example.com/api/v4/projects/5/snippets/11/notes?body=note
+```
+
 ### Delete a snippet note

 Deletes an existing note of a snippet.
@@ -221,7 +252,7 @@ Parameters:

 | Attribute | Type | Required | Description |
 | --------- | ---- | -------- | ----------- |
-| `id` | integer/string | yes | The ID or [URL-encoded path of the project](README.md#namespaced-path-encoding) owned by the authenticated user |
+| `id` | integer/string | yes | The ID or [URL-encoded path of the project](README.md#namespaced-path-encoding) |
 | `snippet_id` | integer | yes | The ID of a snippet |
 | `note_id` | integer | yes | The ID of a note |

@@ -242,11 +273,15 @@ GET /projects/:id/merge_requests/:merge_request_iid/notes?sort=asc&order_by=upda

 | Attribute           | Type             | Required   | Description                                                                                                                                         |
 | ------------------- | ---------------- | ---------- | --------------------------------------------------------------------------------------------------------------------------------------------------- |
-| `id`                | integer/string   | yes        | The ID or [URL-encoded path of the project](README.md#namespaced-path-encoding) owned by the authenticated user
+| `id`                | integer/string   | yes        | The ID or [URL-encoded path of the project](README.md#namespaced-path-encoding)
 | `merge_request_iid` | integer          | yes        | The IID of a project merge request
 | `sort`              | string           | no         | Return merge request notes sorted in `asc` or `desc` order. Default is `desc`
 | `order_by`          | string           | no         | Return merge request notes ordered by `created_at` or `updated_at` fields. Default is `created_at`

+```bash
+curl --request GET --header "PRIVATE-TOKEN: 9koXpg98eAheJpvBs5tK" https://gitlab.example.com/api/v4/projects/5/merge_requests/11/notes
+```
+
 ### Get single merge request note

 Returns a single note for a given merge request.
@@ -257,7 +292,7 @@ GET /projects/:id/merge_requests/:merge_request_iid/notes/:note_id

 Parameters:

- `id` (required) - The ID or [URL-encoded path of the project](README.md#namespaced-path-encoding) owned by the authenticated user
+- `id` (required) - The ID or [URL-encoded path of the project](README.md#namespaced-path-encoding)
 - `merge_request_iid` (required) - The IID of a project merge request
 - `note_id` (required) - The ID of a merge request note

@@ -283,6 +318,10 @@ Parameters:
 }
 ```

+```bash
+curl --request GET --header "PRIVATE-TOKEN: 9koXpg98eAheJpvBs5tK" https://gitlab.example.com/api/v4/projects/5/merge_requests/11/notes/1
+```
+
 ### Create new merge request note

 Creates a new note for a single merge request.
@@ -295,7 +334,7 @@ POST /projects/:id/merge_requests/:merge_request_iid/notes

 Parameters:

- `id` (required) - The ID or [URL-encoded path of the project](README.md#namespaced-path-encoding) owned by the authenticated user
+- `id` (required) - The ID or [URL-encoded path of the project](README.md#namespaced-path-encoding)
 - `merge_request_iid` (required) - The IID of a merge request
 - `body` (required) - The content of a note

@@ -309,11 +348,15 @@ PUT /projects/:id/merge_requests/:merge_request_iid/notes/:note_id

 Parameters:

- `id` (required) - The ID or [URL-encoded path of the project](README.md#namespaced-path-encoding) owned by the authenticated user
+- `id` (required) - The ID or [URL-encoded path of the project](README.md#namespaced-path-encoding)
 - `merge_request_iid` (required) - The IID of a merge request
 - `note_id` (required) - The ID of a note
 - `body` (required) - The content of a note

+```bash
+curl --request PUT --header "PRIVATE-TOKEN: 9koXpg98eAheJpvBs5tK" https://gitlab.example.com/api/v4/projects/5/merge_requests/11/notes?body=note
+```
+
 ### Delete a merge request note

 Deletes an existing note of a merge request.
@@ -326,7 +369,7 @@ Parameters:

 | Attribute | Type | Required | Description |
 | --------- | ---- | -------- | ----------- |
-| `id` | integer/string | yes | The ID or [URL-encoded path of the project](README.md#namespaced-path-encoding) owned by the authenticated user |
+| `id` | integer/string | yes | The ID or [URL-encoded path of the project](README.md#namespaced-path-encoding) |
 | `merge_request_iid` | integer | yes | The IID of a merge request |
 | `note_id` | integer | yes | The ID of a note |


--- a/lib/api/api.rb
+++ b/lib/api/api.rb
@@ -134,6 +134,7 @@ module API
    mount ::API::MergeRequests
    mount ::API::Namespaces
    mount ::API::Notes
+    mount ::API::Discussions
    mount ::API::NotificationSettings
    mount ::API::PagesDomains
    mount ::API::Pipelines

--- a/lib/api/discussions.rb
+++ b/lib/api/discussions.rb
+module API
+  class Discussions < Grape::API
+    include PaginationParams
+    helpers ::API::Helpers::NotesHelpers
+
+    before { authenticate! }
+
+    NOTEABLE_TYPES = [Issue, Snippet].freeze
+
+    NOTEABLE_TYPES.each do |noteable_type|
+      parent_type = noteable_type.parent_class.to_s.underscore
+      noteables_str = noteable_type.to_s.underscore.pluralize
+
+      params do
+        requires :id, type: String, desc: "The ID of a #{parent_type}"
+      end
+      resource parent_type.pluralize.to_sym, requirements: API::PROJECT_ENDPOINT_REQUIREMENTS do
+        desc "Get a list of #{noteable_type.to_s.downcase} discussions" do
+          success Entities::Discussion
+        end
+        params do
+          requires :noteable_id, type: Integer, desc: 'The ID of the noteable'
+          use :pagination
+        end
+        get ":id/#{noteables_str}/:noteable_id/discussions" do
+          noteable = find_noteable(parent_type, noteables_str, params[:noteable_id])
+
+          return not_found!("Discussions") unless can?(current_user, noteable_read_ability_name(noteable), noteable)
+
+          notes = noteable.notes
+            .inc_relations_for_view
+            .includes(:noteable)
+            .fresh
+
+          notes = notes.reject { |n| n.cross_reference_not_visible_for?(current_user) }
+          discussions = Kaminari.paginate_array(Discussion.build_collection(notes, noteable))
+
+          present paginate(discussions), with: Entities::Discussion
+        end
+
+        desc "Get a single #{noteable_type.to_s.downcase} discussion" do
+          success Entities::Discussion
+        end
+        params do
+          requires :discussion_id, type: String, desc: 'The ID of a discussion'
+          requires :noteable_id, type: Integer, desc: 'The ID of the noteable'
+        end
+        get ":id/#{noteables_str}/:noteable_id/discussions/:discussion_id" do
+          noteable = find_noteable(parent_type, noteables_str, params[:noteable_id])
+          notes = readable_discussion_notes(noteable, params[:discussion_id])
+
+          if notes.empty? || !can?(current_user, noteable_read_ability_name(noteable), noteable)
+            return not_found!("Discussion")
+          end
+
+          discussion = Discussion.build(notes, noteable)
+
+          present discussion, with: Entities::Discussion
+        end
+
+        desc "Create a new #{noteable_type.to_s.downcase} discussion" do
+          success Entities::Discussion
+        end
+        params do
+          requires :noteable_id, type: Integer, desc: 'The ID of the noteable'
+          requires :body, type: String, desc: 'The content of a note'
+          optional :created_at, type: String, desc: 'The creation date of the note'
+        end
+        post ":id/#{noteables_str}/:noteable_id/discussions" do
+          noteable = find_noteable(parent_type, noteables_str, params[:noteable_id])
+
+          opts = {
+            note: params[:body],
+            created_at: params[:created_at],
+            type: 'DiscussionNote',
+            noteable_type: noteables_str.classify,
+            noteable_id: noteable.id
+          }
+
+          note = create_note(noteable, opts)
+
+          if note.valid?
+            present note.discussion, with: Entities::Discussion
+          else
+            bad_request!("Note #{note.errors.messages}")
+          end
+        end
+
+        desc "Get comments in a single #{noteable_type.to_s.downcase} discussion" do
+          success Entities::Discussion
+        end
+        params do
+          requires :discussion_id, type: String, desc: 'The ID of a discussion'
+          requires :noteable_id, type: Integer, desc: 'The ID of the noteable'
+        end
+        get ":id/#{noteables_str}/:noteable_id/discussions/:discussion_id/notes" do
+          noteable = find_noteable(parent_type, noteables_str, params[:noteable_id])
+          notes = readable_discussion_notes(noteable, params[:discussion_id])
+
+          if notes.empty? || !can?(current_user, noteable_read_ability_name(noteable), noteable)
+            return not_found!("Notes")
+          end
+
+          present notes, with: Entities::Note
+        end
+
+        desc "Add a comment to a #{noteable_type.to_s.downcase} discussion" do
+          success Entities::Note
+        end
+        params do
+          requires :noteable_id, type: Integer, desc: 'The ID of the noteable'
+          requires :discussion_id, type: String, desc: 'The ID of a discussion'
+          requires :body, type: String, desc: 'The content of a note'
+          optional :created_at, type: String, desc: 'The creation date of the note'
+        end
+        post ":id/#{noteables_str}/:noteable_id/discussions/:discussion_id/notes" do
+          noteable = find_noteable(parent_type, noteables_str, params[:noteable_id])
+          notes = readable_discussion_notes(noteable, params[:discussion_id])
+
+          return not_found!("Discussion") if notes.empty?
+          return bad_request!("Discussion is an individual note.") unless notes.first.part_of_discussion?
+
+          opts = {
+            note: params[:body],
+            type: 'DiscussionNote',
+            in_reply_to_discussion_id: params[:discussion_id],
+            created_at: params[:created_at]
+          }
+          note = create_note(noteable, opts)
+
+          if note.valid?
+            present note, with: Entities::Note
+          else
+            bad_request!("Note #{note.errors.messages}")
+          end
+        end
+
+        desc "Get a comment in a #{noteable_type.to_s.downcase} discussion" do
+          success Entities::Note
+        end
+        params do
+          requires :noteable_id, type: Integer, desc: 'The ID of the noteable'
+          requires :discussion_id, type: String, desc: 'The ID of a discussion'
+          requires :note_id, type: Integer, desc: 'The ID of a note'
+        end
+        get ":id/#{noteables_str}/:noteable_id/discussions/:discussion_id/notes/:note_id" do
+          noteable = find_noteable(parent_type, noteables_str, params[:noteable_id])
+
+          get_note(noteable, params[:note_id])
+        end
+
+        desc "Edit a comment in a #{noteable_type.to_s.downcase} discussion" do
+          success Entities::Note
+        end
+        params do
+          requires :noteable_id, type: Integer, desc: 'The ID of the noteable'
+          requires :discussion_id, type: String, desc: 'The ID of a discussion'
+          requires :note_id, type: Integer, desc: 'The ID of a note'
+          requires :body, type: String, desc: 'The content of a note'
+        end
+        put ":id/#{noteables_str}/:noteable_id/discussions/:discussion_id/notes/:note_id" do
+          noteable = find_noteable(parent_type, noteables_str, params[:noteable_id])
+
+          update_note(noteable, params[:note_id])
+        end
+
+        desc "Delete a comment in a #{noteable_type.to_s.downcase} discussion" do
+          success Entities::Note
+        end
+        params do
+          requires :noteable_id, type: Integer, desc: 'The ID of the noteable'
+          requires :discussion_id, type: String, desc: 'The ID of a discussion'
+          requires :note_id, type: Integer, desc: 'The ID of a note'
+        end
+        delete ":id/#{noteables_str}/:noteable_id/discussions/:discussion_id/notes/:note_id" do
+          noteable = find_noteable(parent_type, noteables_str, params[:noteable_id])
+
+          delete_note(noteable, params[:note_id])
+        end
+      end
+    end
+
+    helpers do
+      def readable_discussion_notes(noteable, discussion_id)
+        notes = noteable.notes
+          .where(discussion_id: discussion_id)
+          .inc_relations_for_view
+          .includes(:noteable)
+          .fresh
+
+        notes.reject { |n| n.cross_reference_not_visible_for?(current_user) }
+      end
+    end
+  end
+end
--- a/lib/api/entities.rb
+++ b/lib/api/entities.rb
@@ -629,6 +629,7 @@ module API
      NOTEABLE_TYPES_WITH_IID = %w(Issue MergeRequest).freeze

      expose :id
+      expose :type
      expose :note, as: :body
      expose :attachment_identifier, as: :attachment
      expose :author, using: Entities::UserBasic
@@ -640,6 +641,12 @@ module API
      expose(:noteable_iid) { |note| note.noteable.iid if NOTEABLE_TYPES_WITH_IID.include?(note.noteable_type) }
    end

+    class Discussion < Grape::Entity
+      expose :id
+      expose :individual_note?, as: :individual_note
+      expose :notes, using: Entities::Note
+    end
+
    class AwardEmoji < Grape::Entity
      expose :id
      expose :name

--- a/lib/api/helpers/notes_helpers.rb
+++ b/lib/api/helpers/notes_helpers.rb
+module API
+  module Helpers
+    module NotesHelpers
+      def update_note(noteable, note_id)
+        note = noteable.notes.find(params[:note_id])
+
+        authorize! :admin_note, note
+
+        opts = {
+          note: params[:body]
+        }
+        parent = noteable_parent(noteable)
+        project = parent if parent.is_a?(Project)
+
+        note = ::Notes::UpdateService.new(project, current_user, opts).execute(note)
+
+        if note.valid?
+          present note, with: Entities::Note
+        else
+          bad_request!("Failed to save note #{note.errors.messages}")
+        end
+      end
+
+      def delete_note(noteable, note_id)
+        note = noteable.notes.find(note_id)
+
+        authorize! :admin_note, note
+
+        parent = noteable_parent(noteable)
+        project = parent if parent.is_a?(Project)
+        destroy_conditionally!(note) do |note|
+          ::Notes::DestroyService.new(project, current_user).execute(note)
+        end
+      end
+
+      def get_note(noteable, note_id)
+        note = noteable.notes.with_metadata.find(params[:note_id])
+        can_read_note = can?(current_user, noteable_read_ability_name(noteable), noteable) && !note.cross_reference_not_visible_for?(current_user)
+
+        if can_read_note
+          present note, with: Entities::Note
+        else
+          not_found!("Note")
+        end
+      end
+
+      def noteable_read_ability_name(noteable)
+        "read_#{noteable.class.to_s.underscore}".to_sym
+      end
+
+      def find_noteable(parent, noteables_str, noteable_id)
+        public_send("find_#{parent}_#{noteables_str.singularize}", noteable_id) # rubocop:disable GitlabSecurity/PublicSend
+      end
+
+      def noteable_parent(noteable)
+        public_send("user_#{noteable.class.parent_class.to_s.underscore}") # rubocop:disable GitlabSecurity/PublicSend
+      end
+
+      def create_note(noteable, opts)
+        noteables_str = noteable.model_name.to_s.underscore.pluralize
+
+        return not_found!(noteables_str) unless can?(current_user, noteable_read_ability_name(noteable), noteable)
+
+        authorize! :create_note, noteable
+
+        parent = noteable_parent(noteable)
+        if opts[:created_at]
+          opts.delete(:created_at) unless current_user.admin? || parent.owner == current_user
+        end
+
+        project = parent if parent.is_a?(Project)
+        ::Notes::CreateService.new(project, current_user, opts).execute
+      end
+    end
+  end
+end
--- a/lib/api/notes.rb
+++ b/lib/api/notes.rb
 module API
  class Notes < Grape::API
    include PaginationParams
+    helpers ::API::Helpers::NotesHelpers

    before { authenticate! }

    NOTEABLE_TYPES = [Issue, MergeRequest, Snippet].freeze

+    NOTEABLE_TYPES.each do |noteable_type|
+      parent_type = noteable_type.parent_class.to_s.underscore
+      noteables_str = noteable_type.to_s.underscore.pluralize
+
      params do
-      requires :id, type: String, desc: 'The ID of a project'
+        requires :id, type: String, desc: "The ID of a #{parent_type}"
      end
-    resource :projects, requirements: API::PROJECT_ENDPOINT_REQUIREMENTS do
-      NOTEABLE_TYPES.each do |noteable_type|
+      resource parent_type.pluralize.to_sym, requirements: API::PROJECT_ENDPOINT_REQUIREMENTS do
        noteables_str = noteable_type.to_s.underscore.pluralize

-        desc 'Get a list of project +noteable+ notes' do
+        desc "Get a list of #{noteable_type.to_s.downcase} notes" do
          success Entities::Note
        end
        params do
@@ -25,7 +29,7 @@ module API
          use :pagination
        end
        get ":id/#{noteables_str}/:noteable_id/notes" do
-          noteable = find_project_noteable(noteables_str, params[:noteable_id])
+          noteable = find_noteable(parent_type, noteables_str, params[:noteable_id])

          if can?(current_user, noteable_read_ability_name(noteable), noteable)
            # We exclude notes that are cross-references and that cannot be viewed
@@ -46,7 +50,7 @@ module API
          end
        end

-        desc 'Get a single +noteable+ note' do
+        desc "Get a single #{noteable_type.to_s.downcase} note" do
          success Entities::Note
        end
        params do
@@ -54,18 +58,11 @@ module API
          requires :noteable_id, type: Integer, desc: 'The ID of the noteable'
        end
        get ":id/#{noteables_str}/:noteable_id/notes/:note_id" do
-          noteable = find_project_noteable(noteables_str, params[:noteable_id])
-          note = noteable.notes.with_metadata.find(params[:note_id])
-          can_read_note = can?(current_user, noteable_read_ability_name(noteable), noteable) && !note.cross_reference_not_visible_for?(current_user)
-
-          if can_read_note
-            present note, with: Entities::Note
-          else
-            not_found!("Note")
-          end
+          noteable = find_noteable(parent_type, noteables_str, params[:noteable_id])
+          get_note(noteable, params[:note_id])
        end

-        desc 'Create a new +noteable+ note' do
+        desc "Create a new #{noteable_type.to_s.downcase} note" do
          success Entities::Note
        end
        params do
@@ -74,34 +71,25 @@ module API
          optional :created_at, type: String, desc: 'The creation date of the note'
        end
        post ":id/#{noteables_str}/:noteable_id/notes" do
-          noteable = find_project_noteable(noteables_str, params[:noteable_id])
+          noteable = find_noteable(parent_type, noteables_str, params[:noteable_id])

          opts = {
            note: params[:body],
            noteable_type: noteables_str.classify,
-            noteable_id: noteable.id
+            noteable_id: noteable.id,
+            created_at: params[:created_at]
          }

-          if can?(current_user, noteable_read_ability_name(noteable), noteable)
-            authorize! :create_note, noteable
-
-            if params[:created_at] && (current_user.admin? || user_project.owner == current_user)
-              opts[:created_at] = params[:created_at]
-            end
-
-            note = ::Notes::CreateService.new(user_project, current_user, opts).execute
+          note = create_note(noteable, opts)

          if note.valid?
            present note, with: Entities.const_get(note.class.name)
          else
-              not_found!("Note #{note.errors.messages}")
-            end
-          else
-            not_found!("Note")
+            bad_request!("Note #{note.errors.messages}")
          end
        end

-        desc 'Update an existing +noteable+ note' do
+        desc "Update an existing #{noteable_type.to_s.downcase} note" do
          success Entities::Note
        end
        params do
@@ -110,24 +98,12 @@ module API
          requires :body, type: String, desc: 'The content of a note'
        end
        put ":id/#{noteables_str}/:noteable_id/notes/:note_id" do
-          note = user_project.notes.find(params[:note_id])
-
-          authorize! :admin_note, note
+          noteable = find_noteable(parent_type, noteables_str, params[:noteable_id])

-          opts = {
-            note: params[:body]
-          }
-
-          note = ::Notes::UpdateService.new(user_project, current_user, opts).execute(note)
-
-          if note.valid?
-            present note, with: Entities::Note
-          else
-            render_api_error!("Failed to save note #{note.errors.messages}", 400)
-          end
+          update_note(noteable, params[:note_id])
        end

-        desc 'Delete a +noteable+ note' do
+        desc "Delete a #{noteable_type.to_s.downcase} note" do
          success Entities::Note
        end
        params do
@@ -135,24 +111,10 @@ module API
          requires :note_id, type: Integer, desc: 'The ID of a note'
        end
        delete ":id/#{noteables_str}/:noteable_id/notes/:note_id" do
-          note = user_project.notes.find(params[:note_id])
+          noteable = find_noteable(parent_type, noteables_str, params[:noteable_id])

-          authorize! :admin_note, note
-
-          destroy_conditionally!(note) do |note|
-            ::Notes::DestroyService.new(user_project, current_user).execute(note)
-          end
-        end
-      end
+          delete_note(noteable, params[:note_id])
        end
-
-    helpers do
-      def find_project_noteable(noteables_str, noteable_id)
-        public_send("find_project_#{noteables_str.singularize}", noteable_id) # rubocop:disable GitlabSecurity/PublicSend
-      end
-
-      def noteable_read_ability_name(noteable)
-        "read_#{noteable.class.to_s.underscore}".to_sym
      end
    end
  end

--- a/spec/factories/notes.rb
+++ b/spec/factories/notes.rb
@@ -16,6 +16,8 @@ FactoryBot.define do
    factory :note_on_personal_snippet,   traits: [:on_personal_snippet]
    factory :system_note,                traits: [:system]

+    factory :discussion_note, class: DiscussionNote
+
    factory :discussion_note_on_merge_request, traits: [:on_merge_request], class: DiscussionNote do
      association :project, :repository

@@ -31,6 +33,8 @@ FactoryBot.define do

    factory :discussion_note_on_personal_snippet, traits: [:on_personal_snippet], class: DiscussionNote

+    factory :discussion_note_on_snippet, traits: [:on_snippet], class: DiscussionNote
+
    factory :legacy_diff_note_on_commit, traits: [:on_commit, :legacy_diff_note], class: LegacyDiffNote

    factory :legacy_diff_note_on_merge_request, traits: [:on_merge_request, :legacy_diff_note], class: LegacyDiffNote do
@@ -96,6 +100,10 @@ FactoryBot.define do
      noteable { create(:issue, project: project) }
    end

+    trait :on_snippet do
+      noteable { create(:snippet, project: project) }
+    end
+
    trait :on_merge_request do
      noteable { create(:merge_request, source_project: project) }
    end

--- a/spec/fixtures/api/schemas/public_api/v4/notes.json
+++ b/spec/fixtures/api/schemas/public_api/v4/notes.json
@@ -4,6 +4,7 @@
    "type": "object",
    "properties" : {
      "id": { "type": "integer" },
+      "type": { "type": ["string", "null"] },
      "body": { "type": "string" },
      "attachment": { "type": ["string", "null"] },
      "author": {

--- a/spec/requests/api/discussions_spec.rb
+++ b/spec/requests/api/discussions_spec.rb
+require 'spec_helper'
+
+describe API::Discussions do
+  let(:user) { create(:user) }
+  let!(:project) { create(:project, :public, namespace: user.namespace) }
+  let(:private_user)    { create(:user) }
+
+  before do
+    project.add_reporter(user)
+  end
+
+  context "when noteable is an Issue" do
+    let!(:issue) { create(:issue, project: project, author: user) }
+    let!(:issue_note) { create(:discussion_note_on_issue, noteable: issue, project: project, author: user) }
+
+    it_behaves_like "discussions API", 'projects', 'issues', 'iid' do
+      let(:parent) { project }
+      let(:noteable) { issue }
+      let(:note) { issue_note }
+    end
+  end
+
+  context "when noteable is a Snippet" do
+    let!(:snippet) { create(:project_snippet, project: project, author: user) }
+    let!(:snippet_note) { create(:discussion_note_on_snippet, noteable: snippet, project: project, author: user) }
+
+    it_behaves_like "discussions API", 'projects', 'snippets', 'id' do
+      let(:parent) { project }
+      let(:noteable) { snippet }
+      let(:note) { snippet_note }
+    end
+  end
+end
--- a/spec/requests/api/notes_spec.rb
+++ b/spec/requests/api/notes_spec.rb
@@ -3,95 +3,63 @@ require 'spec_helper'
 describe API::Notes do
  let(:user) { create(:user) }
  let!(:project) { create(:project, :public, namespace: user.namespace) }
-  let!(:issue) { create(:issue, project: project, author: user) }
-  let!(:merge_request) { create(:merge_request, source_project: project, target_project: project, author: user) }
-  let!(:snippet) { create(:project_snippet, project: project, author: user) }
-  let!(:issue_note) { create(:note, noteable: issue, project: project, author: user) }
-  let!(:merge_request_note) { create(:note, noteable: merge_request, project: project, author: user) }
-  let!(:snippet_note) { create(:note, noteable: snippet, project: project, author: user) }
-
-  # For testing the cross-reference of a private issue in a public issue
  let(:private_user)    { create(:user) }
-  let(:private_project) do
-    create(:project, namespace: private_user.namespace)
-    .tap { |p| p.add_master(private_user) }
-  end
-  let(:private_issue)    { create(:issue, project: private_project) }
-
-  let(:ext_proj)  { create(:project, :public) }
-  let(:ext_issue) { create(:issue, project: ext_proj) }
-
-  let!(:cross_reference_note) do
-    create :note,
-    noteable: ext_issue, project: ext_proj,
-    note: "mentioned in issue #{private_issue.to_reference(ext_proj)}",
-    system: true
-  end

  before do
    project.add_reporter(user)
  end

-  describe "GET /projects/:id/noteable/:noteable_id/notes" do
  context "when noteable is an Issue" do
-      context 'sorting' do
-        before do
-          create_list(:note, 3, noteable: issue, project: project, author: user)
-        end
-
-        it 'sorts by created_at in descending order by default' do
-          get api("/projects/#{project.id}/issues/#{issue.iid}/notes", user)
-
-          response_dates = json_response.map { |noteable| noteable['created_at'] }
+    let!(:issue) { create(:issue, project: project, author: user) }
+    let!(:issue_note) { create(:note, noteable: issue, project: project, author: user) }

-          expect(json_response.length).to eq(4)
-          expect(response_dates).to eq(response_dates.sort.reverse)
+    it_behaves_like "noteable API", 'projects', 'issues', 'iid' do
+      let(:parent) { project }
+      let(:noteable) { issue }
+      let(:note) { issue_note }
    end

-        it 'sorts by ascending order when requested' do
-          get api("/projects/#{project.id}/issues/#{issue.iid}/notes?sort=asc", user)
-
-          response_dates = json_response.map { |noteable| noteable['created_at'] }
+    context 'when user does not have access to create noteable' do
+      let(:private_issue) { create(:issue, project: create(:project, :private)) }

-          expect(json_response.length).to eq(4)
-          expect(response_dates).to eq(response_dates.sort)
+      ##
+      # We are posting to project user has access to, but we use issue id
+      # from a different project, see #15577
+      #
+      before do
+        post api("/projects/#{private_issue.project.id}/issues/#{private_issue.iid}/notes", user),
+             body: 'Hi!'
      end

-        it 'sorts by updated_at in descending order when requested' do
-          get api("/projects/#{project.id}/issues/#{issue.iid}/notes?order_by=updated_at", user)
-
-          response_dates = json_response.map { |noteable| noteable['updated_at'] }
-
-          expect(json_response.length).to eq(4)
-          expect(response_dates).to eq(response_dates.sort.reverse)
+      it 'responds with resource not found error' do
+        expect(response.status).to eq 404
      end

-        it 'sorts by updated_at in ascending order when requested' do
-          get api("/projects/#{project.id}/issues/#{issue.iid}/notes??order_by=updated_at&sort=asc", user)
-
-          response_dates = json_response.map { |noteable| noteable['updated_at'] }
-
-          expect(json_response.length).to eq(4)
-          expect(response_dates).to eq(response_dates.sort)
+      it 'does not create new note' do
+        expect(private_issue.notes.reload).to be_empty
      end
    end

-      it "returns an array of issue notes" do
-        get api("/projects/#{project.id}/issues/#{issue.iid}/notes", user)
-
-        expect(response).to have_gitlab_http_status(200)
-        expect(response).to include_pagination_headers
-        expect(json_response).to be_an Array
-        expect(json_response.first['body']).to eq(issue_note.note)
+    context "when referencing other project" do
+      # For testing the cross-reference of a private issue in a public project
+      let(:private_project) do
+        create(:project, namespace: private_user.namespace)
+        .tap { |p| p.add_master(private_user) }
      end
+      let(:private_issue)    { create(:issue, project: private_project) }

-      it "returns a 404 error when issue id not found" do
-        get api("/projects/#{project.id}/issues/12345/notes", user)
+      let(:ext_proj)  { create(:project, :public) }
+      let(:ext_issue) { create(:issue, project: ext_proj) }

-        expect(response).to have_gitlab_http_status(404)
+      let!(:cross_reference_note) do
+        create :note,
+        noteable: ext_issue, project: ext_proj,
+        note: "mentioned in issue #{private_issue.to_reference(ext_proj)}",
+        system: true
      end

-      context "and current user cannot view the notes" do
+      describe "GET /projects/:id/noteable/:noteable_id/notes" do
+        context "current user cannot view the notes" do
          it "returns an empty array" do
            get api("/projects/#{ext_proj.id}/issues/#{ext_issue.iid}/notes", user)

@@ -101,7 +69,7 @@ describe API::Notes do
            expect(json_response).to be_empty
          end

-        context "and issue is confidential" do
+          context "issue is confidential" do
            before do
              ext_issue.update_attributes(confidential: true)
            end
@@ -112,8 +80,9 @@ describe API::Notes do
              expect(response).to have_gitlab_http_status(404)
            end
          end
+        end

-        context "and current user can view the note" do
+        context "current user can view the note" do
          it "returns an empty array" do
            get api("/projects/#{ext_proj.id}/issues/#{ext_issue.iid}/notes", private_user)

@@ -124,153 +93,9 @@ describe API::Notes do
          end
        end
      end
-    end
-
-    context "when noteable is a Snippet" do
-      context 'sorting' do
-        before do
-          create_list(:note, 3, noteable: snippet, project: project, author: user)
-        end
-
-        it 'sorts by created_at in descending order by default' do
-          get api("/projects/#{project.id}/snippets/#{snippet.id}/notes", user)
-
-          response_dates = json_response.map { |noteable| noteable['created_at'] }
-
-          expect(json_response.length).to eq(4)
-          expect(response_dates).to eq(response_dates.sort.reverse)
-        end
-
-        it 'sorts by ascending order when requested' do
-          get api("/projects/#{project.id}/snippets/#{snippet.id}/notes?sort=asc", user)
-
-          response_dates = json_response.map { |noteable| noteable['created_at'] }
-
-          expect(json_response.length).to eq(4)
-          expect(response_dates).to eq(response_dates.sort)
-        end
-
-        it 'sorts by updated_at in descending order when requested' do
-          get api("/projects/#{project.id}/snippets/#{snippet.id}/notes?order_by=updated_at", user)
-
-          response_dates = json_response.map { |noteable| noteable['updated_at'] }
-
-          expect(json_response.length).to eq(4)
-          expect(response_dates).to eq(response_dates.sort.reverse)
-        end
-
-        it 'sorts by updated_at in ascending order when requested' do
-          get api("/projects/#{project.id}/snippets/#{snippet.id}/notes??order_by=updated_at&sort=asc", user)
-
-          response_dates = json_response.map { |noteable| noteable['updated_at'] }
-
-          expect(json_response.length).to eq(4)
-          expect(response_dates).to eq(response_dates.sort)
-        end
-      end
-      it "returns an array of snippet notes" do
-        get api("/projects/#{project.id}/snippets/#{snippet.id}/notes", user)
-
-        expect(response).to have_gitlab_http_status(200)
-        expect(response).to include_pagination_headers
-        expect(json_response).to be_an Array
-        expect(json_response.first['body']).to eq(snippet_note.note)
-      end
-
-      it "returns a 404 error when snippet id not found" do
-        get api("/projects/#{project.id}/snippets/42/notes", user)
-
-        expect(response).to have_gitlab_http_status(404)
-      end
-
-      it "returns 404 when not authorized" do
-        get api("/projects/#{project.id}/snippets/#{snippet.id}/notes", private_user)
-
-        expect(response).to have_gitlab_http_status(404)
-      end
-    end
-
-    context "when noteable is a Merge Request" do
-      context 'sorting' do
-        before do
-          create_list(:note, 3, noteable: merge_request, project: project, author: user)
-        end
-
-        it 'sorts by created_at in descending order by default' do
-          get api("/projects/#{project.id}/merge_requests/#{merge_request.iid}/notes", user)
-
-          response_dates = json_response.map { |noteable| noteable['created_at'] }
-
-          expect(json_response.length).to eq(4)
-          expect(response_dates).to eq(response_dates.sort.reverse)
-        end
-
-        it 'sorts by ascending order when requested' do
-          get api("/projects/#{project.id}/merge_requests/#{merge_request.iid}/notes?sort=asc", user)
-
-          response_dates = json_response.map { |noteable| noteable['created_at'] }
-
-          expect(json_response.length).to eq(4)
-          expect(response_dates).to eq(response_dates.sort)
-        end
-
-        it 'sorts by updated_at in descending order when requested' do
-          get api("/projects/#{project.id}/merge_requests/#{merge_request.iid}/notes?order_by=updated_at", user)
-
-          response_dates = json_response.map { |noteable| noteable['updated_at'] }
-
-          expect(json_response.length).to eq(4)
-          expect(response_dates).to eq(response_dates.sort.reverse)
-        end
-
-        it 'sorts by updated_at in ascending order when requested' do
-          get api("/projects/#{project.id}/merge_requests/#{merge_request.iid}/notes??order_by=updated_at&sort=asc", user)
-
-          response_dates = json_response.map { |noteable| noteable['updated_at'] }
-
-          expect(json_response.length).to eq(4)
-          expect(response_dates).to eq(response_dates.sort)
-        end
-      end
-      it "returns an array of merge_requests notes" do
-        get api("/projects/#{project.id}/merge_requests/#{merge_request.iid}/notes", user)
-
-        expect(response).to have_gitlab_http_status(200)
-        expect(response).to include_pagination_headers
-        expect(json_response).to be_an Array
-        expect(json_response.first['body']).to eq(merge_request_note.note)
-      end
-
-      it "returns a 404 error if merge request id not found" do
-        get api("/projects/#{project.id}/merge_requests/4444/notes", user)
-
-        expect(response).to have_gitlab_http_status(404)
-      end
-
-      it "returns 404 when not authorized" do
-        get api("/projects/#{project.id}/merge_requests/4444/notes", private_user)
-
-        expect(response).to have_gitlab_http_status(404)
-      end
-    end
-  end

      describe "GET /projects/:id/noteable/:noteable_id/notes/:note_id" do
-    context "when noteable is an Issue" do
-      it "returns an issue note by id" do
-        get api("/projects/#{project.id}/issues/#{issue.iid}/notes/#{issue_note.id}", user)
-
-        expect(response).to have_gitlab_http_status(200)
-        expect(json_response['body']).to eq(issue_note.note)
-      end
-
-      it "returns a 404 error if issue note not found" do
-        get api("/projects/#{project.id}/issues/#{issue.iid}/notes/12345", user)
-
-        expect(response).to have_gitlab_http_status(404)
-      end
-
-      context "and current user cannot view the note" do
+        context "current user cannot view the notes" do
          it "returns a 404 error" do
            get api("/projects/#{ext_proj.id}/issues/#{ext_issue.iid}/notes/#{cross_reference_note.id}", user)

@@ -288,8 +113,9 @@ describe API::Notes do
              expect(response).to have_gitlab_http_status(404)
            end
          end
+        end

-        context "and current user can view the note" do
+        context "current user can view the note" do
          it "returns an issue note by id" do
            get api("/projects/#{ext_proj.id}/issues/#{ext_issue.iid}/notes/#{cross_reference_note.id}", private_user)

@@ -299,132 +125,27 @@ describe API::Notes do
        end
      end
    end
-
-    context "when noteable is a Snippet" do
-      it "returns a snippet note by id" do
-        get api("/projects/#{project.id}/snippets/#{snippet.id}/notes/#{snippet_note.id}", user)
-
-        expect(response).to have_gitlab_http_status(200)
-        expect(json_response['body']).to eq(snippet_note.note)
-      end
-
-      it "returns a 404 error if snippet note not found" do
-        get api("/projects/#{project.id}/snippets/#{snippet.id}/notes/12345", user)
-
-        expect(response).to have_gitlab_http_status(404)
-      end
-    end
-  end
-
-  describe "POST /projects/:id/noteable/:noteable_id/notes" do
-    context "when noteable is an Issue" do
-      it "creates a new issue note" do
-        post api("/projects/#{project.id}/issues/#{issue.iid}/notes", user), body: 'hi!'
-
-        expect(response).to have_gitlab_http_status(201)
-        expect(json_response['body']).to eq('hi!')
-        expect(json_response['author']['username']).to eq(user.username)
-      end
-
-      it "returns a 400 bad request error if body not given" do
-        post api("/projects/#{project.id}/issues/#{issue.iid}/notes", user)
-
-        expect(response).to have_gitlab_http_status(400)
-      end
-
-      it "returns a 401 unauthorized error if user not authenticated" do
-        post api("/projects/#{project.id}/issues/#{issue.iid}/notes"), body: 'hi!'
-
-        expect(response).to have_gitlab_http_status(401)
-      end
-
-      context 'when an admin or owner makes the request' do
-        it 'accepts the creation date to be set' do
-          creation_time = 2.weeks.ago
-          post api("/projects/#{project.id}/issues/#{issue.iid}/notes", user),
-            body: 'hi!', created_at: creation_time
-
-          expect(response).to have_gitlab_http_status(201)
-          expect(json_response['body']).to eq('hi!')
-          expect(json_response['author']['username']).to eq(user.username)
-          expect(Time.parse(json_response['created_at'])).to be_like_time(creation_time)
-        end
-      end
-
-      context 'when the user is posting an award emoji on an issue created by someone else' do
-        let(:issue2) { create(:issue, project: project) }
-
-        it 'creates a new issue note' do
-          post api("/projects/#{project.id}/issues/#{issue2.iid}/notes", user), body: ':+1:'
-
-          expect(response).to have_gitlab_http_status(201)
-          expect(json_response['body']).to eq(':+1:')
-        end
-      end
-
-      context 'when the user is posting an award emoji on his/her own issue' do
-        it 'creates a new issue note' do
-          post api("/projects/#{project.id}/issues/#{issue.iid}/notes", user), body: ':+1:'
-
-          expect(response).to have_gitlab_http_status(201)
-          expect(json_response['body']).to eq(':+1:')
-        end
-      end
  end

  context "when noteable is a Snippet" do
-      it "creates a new snippet note" do
-        post api("/projects/#{project.id}/snippets/#{snippet.id}/notes", user), body: 'hi!'
-
-        expect(response).to have_gitlab_http_status(201)
-        expect(json_response['body']).to eq('hi!')
-        expect(json_response['author']['username']).to eq(user.username)
-      end
-
-      it "returns a 400 bad request error if body not given" do
-        post api("/projects/#{project.id}/snippets/#{snippet.id}/notes", user)
-
-        expect(response).to have_gitlab_http_status(400)
-      end
-
-      it "returns a 401 unauthorized error if user not authenticated" do
-        post api("/projects/#{project.id}/snippets/#{snippet.id}/notes"), body: 'hi!'
-
-        expect(response).to have_gitlab_http_status(401)
-      end
-    end
-
-    context 'when user does not have access to read the noteable' do
-      it 'responds with 404' do
-        project = create(:project, :private) { |p| p.add_guest(user) }
-        issue = create(:issue, :confidential, project: project)
-
-        post api("/projects/#{project.id}/issues/#{issue.iid}/notes", user),
-          body: 'Foo'
+    let!(:snippet) { create(:project_snippet, project: project, author: user) }
+    let!(:snippet_note) { create(:note, noteable: snippet, project: project, author: user) }

-        expect(response).to have_gitlab_http_status(404)
+    it_behaves_like "noteable API", 'projects', 'snippets', 'id' do
+      let(:parent) { project }
+      let(:noteable) { snippet }
+      let(:note) { snippet_note }
    end
  end

-    context 'when user does not have access to create noteable' do
-      let(:private_issue) { create(:issue, project: create(:project, :private)) }
-
-      ##
-      # We are posting to project user has access to, but we use issue id
-      # from a different project, see #15577
-      #
-      before do
-        post api("/projects/#{private_issue.project.id}/issues/#{private_issue.iid}/notes", user),
-             body: 'Hi!'
-      end
+  context "when noteable is a Merge Request" do
+    let!(:merge_request) { create(:merge_request, source_project: project, target_project: project, author: user) }
+    let!(:merge_request_note) { create(:note, noteable: merge_request, project: project, author: user) }

-      it 'responds with resource not found error' do
-        expect(response.status).to eq 404
-      end
-
-      it 'does not create new note' do
-        expect(private_issue.notes.reload).to be_empty
-      end
+    it_behaves_like "noteable API", 'projects', 'merge_requests', 'iid' do
+      let(:parent) { project }
+      let(:noteable) { merge_request }
+      let(:note) { merge_request_note }
    end

    context 'when the merge request discussion is locked' do
@@ -461,145 +182,4 @@ describe API::Notes do
      end
    end
  end
-
-  describe "POST /projects/:id/noteable/:noteable_id/notes to test observer on create" do
-    it "creates an activity event when an issue note is created" do
-      expect(Event).to receive(:create!)
-
-      post api("/projects/#{project.id}/issues/#{issue.iid}/notes", user), body: 'hi!'
-    end
-  end
-
-  describe 'PUT /projects/:id/noteable/:noteable_id/notes/:note_id' do
-    context 'when noteable is an Issue' do
-      it 'returns modified note' do
-        put api("/projects/#{project.id}/issues/#{issue.iid}/"\
-                  "notes/#{issue_note.id}", user), body: 'Hello!'
-
-        expect(response).to have_gitlab_http_status(200)
-        expect(json_response['body']).to eq('Hello!')
-      end
-
-      it 'returns a 404 error when note id not found' do
-        put api("/projects/#{project.id}/issues/#{issue.iid}/notes/12345", user),
-                body: 'Hello!'
-
-        expect(response).to have_gitlab_http_status(404)
-      end
-
-      it 'returns a 400 bad request error if body not given' do
-        put api("/projects/#{project.id}/issues/#{issue.iid}/"\
-                  "notes/#{issue_note.id}", user)
-
-        expect(response).to have_gitlab_http_status(400)
-      end
-    end
-
-    context 'when noteable is a Snippet' do
-      it 'returns modified note' do
-        put api("/projects/#{project.id}/snippets/#{snippet.id}/"\
-                  "notes/#{snippet_note.id}", user), body: 'Hello!'
-
-        expect(response).to have_gitlab_http_status(200)
-        expect(json_response['body']).to eq('Hello!')
-      end
-
-      it 'returns a 404 error when note id not found' do
-        put api("/projects/#{project.id}/snippets/#{snippet.id}/"\
-                  "notes/12345", user), body: "Hello!"
-
-        expect(response).to have_gitlab_http_status(404)
-      end
-    end
-
-    context 'when noteable is a Merge Request' do
-      it 'returns modified note' do
-        put api("/projects/#{project.id}/merge_requests/#{merge_request.iid}/"\
-                  "notes/#{merge_request_note.id}", user), body: 'Hello!'
-
-        expect(response).to have_gitlab_http_status(200)
-        expect(json_response['body']).to eq('Hello!')
-      end
-
-      it 'returns a 404 error when note id not found' do
-        put api("/projects/#{project.id}/merge_requests/#{merge_request.iid}/"\
-                  "notes/12345", user), body: "Hello!"
-
-        expect(response).to have_gitlab_http_status(404)
-      end
-    end
-  end
-
-  describe 'DELETE /projects/:id/noteable/:noteable_id/notes/:note_id' do
-    context 'when noteable is an Issue' do
-      it 'deletes a note' do
-        delete api("/projects/#{project.id}/issues/#{issue.iid}/"\
-                   "notes/#{issue_note.id}", user)
-
-        expect(response).to have_gitlab_http_status(204)
-        # Check if note is really deleted
-        delete api("/projects/#{project.id}/issues/#{issue.iid}/"\
-                   "notes/#{issue_note.id}", user)
-        expect(response).to have_gitlab_http_status(404)
-      end
-
-      it 'returns a 404 error when note id not found' do
-        delete api("/projects/#{project.id}/issues/#{issue.iid}/notes/12345", user)
-
-        expect(response).to have_gitlab_http_status(404)
-      end
-
-      it_behaves_like '412 response' do
-        let(:request) { api("/projects/#{project.id}/issues/#{issue.iid}/notes/#{issue_note.id}", user) }
-      end
-    end
-
-    context 'when noteable is a Snippet' do
-      it 'deletes a note' do
-        delete api("/projects/#{project.id}/snippets/#{snippet.id}/"\
-                   "notes/#{snippet_note.id}", user)
-
-        expect(response).to have_gitlab_http_status(204)
-        # Check if note is really deleted
-        delete api("/projects/#{project.id}/snippets/#{snippet.id}/"\
-                   "notes/#{snippet_note.id}", user)
-        expect(response).to have_gitlab_http_status(404)
-      end
-
-      it 'returns a 404 error when note id not found' do
-        delete api("/projects/#{project.id}/snippets/#{snippet.id}/"\
-                   "notes/12345", user)
-
-        expect(response).to have_gitlab_http_status(404)
-      end
-
-      it_behaves_like '412 response' do
-        let(:request) { api("/projects/#{project.id}/snippets/#{snippet.id}/notes/#{snippet_note.id}", user) }
-      end
-    end
-
-    context 'when noteable is a Merge Request' do
-      it 'deletes a note' do
-        delete api("/projects/#{project.id}/merge_requests/"\
-                   "#{merge_request.iid}/notes/#{merge_request_note.id}", user)
-
-        expect(response).to have_gitlab_http_status(204)
-        # Check if note is really deleted
-        delete api("/projects/#{project.id}/merge_requests/"\
-                   "#{merge_request.iid}/notes/#{merge_request_note.id}", user)
-        expect(response).to have_gitlab_http_status(404)
-      end
-
-      it 'returns a 404 error when note id not found' do
-        delete api("/projects/#{project.id}/merge_requests/"\
-                   "#{merge_request.iid}/notes/12345", user)
-
-        expect(response).to have_gitlab_http_status(404)
-      end
-
-      it_behaves_like '412 response' do
-        let(:request) { api("/projects/#{project.id}/merge_requests/#{merge_request.iid}/notes/#{merge_request_note.id}", user) }
-      end
-    end
-  end
 end
--- a/spec/support/shared_examples/requests/api/discussions.rb
+++ b/spec/support/shared_examples/requests/api/discussions.rb
+shared_examples 'discussions API' do |parent_type, noteable_type, id_name|
+  describe "GET /#{parent_type}/:id/#{noteable_type}/:noteable_id/discussions" do
+    it "returns an array of discussions" do
+      get api("/#{parent_type}/#{parent.id}/#{noteable_type}/#{noteable[id_name]}/discussions", user)
+
+      expect(response).to have_gitlab_http_status(200)
+      expect(response).to include_pagination_headers
+      expect(json_response).to be_an Array
+      expect(json_response.first['id']).to eq(note.discussion_id)
+    end
+
+    it "returns a 404 error when noteable id not found" do
+      get api("/#{parent_type}/#{parent.id}/#{noteable_type}/12345/discussions", user)
+
+      expect(response).to have_gitlab_http_status(404)
+    end
+
+    it "returns 404 when not authorized" do
+      parent.update!(visibility_level: Gitlab::VisibilityLevel::PRIVATE)
+
+      get api("/#{parent_type}/#{parent.id}/#{noteable_type}/#{noteable[id_name]}/discussions", private_user)
+
+      expect(response).to have_gitlab_http_status(404)
+    end
+  end
+
+  describe "GET /#{parent_type}/:id/#{noteable_type}/:noteable_id/discussions/:discussion_id" do
+    it "returns a discussion by id" do
+      get api("/#{parent_type}/#{parent.id}/#{noteable_type}/#{noteable[id_name]}/discussions/#{note.discussion_id}", user)
+
+      expect(response).to have_gitlab_http_status(200)
+      expect(json_response['id']).to eq(note.discussion_id)
+      expect(json_response['notes'].first['body']).to eq(note.note)
+    end
+
+    it "returns a 404 error if discussion not found" do
+      get api("/#{parent_type}/#{parent.id}/#{noteable_type}/#{noteable[id_name]}/discussions/12345", user)
+
+      expect(response).to have_gitlab_http_status(404)
+    end
+  end
+
+  describe "POST /#{parent_type}/:id/#{noteable_type}/:noteable_id/discussions" do
+    it "creates a new note" do
+      post api("/#{parent_type}/#{parent.id}/#{noteable_type}/#{noteable[id_name]}/discussions", user), body: 'hi!'
+
+      expect(response).to have_gitlab_http_status(201)
+      expect(json_response['notes'].first['body']).to eq('hi!')
+      expect(json_response['notes'].first['author']['username']).to eq(user.username)
+    end
+
+    it "returns a 400 bad request error if body not given" do
+      post api("/#{parent_type}/#{parent.id}/#{noteable_type}/#{noteable[id_name]}/discussions", user)
+
+      expect(response).to have_gitlab_http_status(400)
+    end
+
+    it "returns a 401 unauthorized error if user not authenticated" do
+      post api("/#{parent_type}/#{parent.id}/#{noteable_type}/#{noteable[id_name]}/discussions"), body: 'hi!'
+
+      expect(response).to have_gitlab_http_status(401)
+    end
+
+    context 'when an admin or owner makes the request' do
+      it 'accepts the creation date to be set' do
+        creation_time = 2.weeks.ago
+        post api("/#{parent_type}/#{parent.id}/#{noteable_type}/#{noteable[id_name]}/discussions", user),
+          body: 'hi!', created_at: creation_time
+
+        expect(response).to have_gitlab_http_status(201)
+        expect(json_response['notes'].first['body']).to eq('hi!')
+        expect(json_response['notes'].first['author']['username']).to eq(user.username)
+        expect(Time.parse(json_response['notes'].first['created_at'])).to be_like_time(creation_time)
+      end
+    end
+
+    context 'when user does not have access to read the discussion' do
+      before do
+        parent.update!(visibility_level: Gitlab::VisibilityLevel::PRIVATE)
+      end
+
+      it 'responds with 404' do
+        post api("/#{parent_type}/#{parent.id}/#{noteable_type}/#{noteable[id_name]}/discussions", private_user),
+          body: 'Foo'
+
+        expect(response).to have_gitlab_http_status(404)
+      end
+    end
+  end
+
+  describe "POST /#{parent_type}/:id/#{noteable_type}/:noteable_id/discussions/:discussion_id/notes" do
+    it 'adds a new note to the discussion' do
+      post api("/#{parent_type}/#{parent.id}/#{noteable_type}/#{noteable[id_name]}/"\
+               "discussions/#{note.discussion_id}/notes", user), body: 'Hello!'
+
+      expect(response).to have_gitlab_http_status(201)
+      expect(json_response['body']).to eq('Hello!')
+      expect(json_response['type']).to eq('DiscussionNote')
+    end
+
+    it 'returns a 400 bad request error if body not given' do
+      post api("/#{parent_type}/#{parent.id}/#{noteable_type}/#{noteable[id_name]}/"\
+               "discussions/#{note.discussion_id}/notes", user)
+
+      expect(response).to have_gitlab_http_status(400)
+    end
+
+    it "returns a 400 bad request error if discussion is individual note" do
+      note.update_attribute(:type, nil)
+
+      post api("/#{parent_type}/#{parent.id}/#{noteable_type}/#{noteable[id_name]}/"\
+               "discussions/#{note.discussion_id}/notes", user), body: 'hi!'
+
+      expect(response).to have_gitlab_http_status(400)
+    end
+  end
+
+  describe "PUT /#{parent_type}/:id/#{noteable_type}/:noteable_id/discussions/:discussion_id/notes/:note_id" do
+    it 'returns modified note' do
+      put api("/#{parent_type}/#{parent.id}/#{noteable_type}/#{noteable[id_name]}/"\
+              "discussions/#{note.discussion_id}/notes/#{note.id}", user), body: 'Hello!'
+
+      expect(response).to have_gitlab_http_status(200)
+      expect(json_response['body']).to eq('Hello!')
+    end
+
+    it 'returns a 404 error when note id not found' do
+      put api("/#{parent_type}/#{parent.id}/#{noteable_type}/#{noteable[id_name]}/"\
+              "discussions/#{note.discussion_id}/notes/12345", user),
+              body: 'Hello!'
+
+      expect(response).to have_gitlab_http_status(404)
+    end
+
+    it 'returns a 400 bad request error if body not given' do
+      put api("/#{parent_type}/#{parent.id}/#{noteable_type}/#{noteable[id_name]}/"\
+              "discussions/#{note.discussion_id}/notes/#{note.id}", user)
+
+      expect(response).to have_gitlab_http_status(400)
+    end
+  end
+
+  describe "DELETE /#{parent_type}/:id/#{noteable_type}/:noteable_id/discussions/:discussion_id/notes/:note_id" do
+    it 'deletes a note' do
+      delete api("/#{parent_type}/#{parent.id}/#{noteable_type}/#{noteable[id_name]}/"\
+                 "discussions/#{note.discussion_id}/notes/#{note.id}", user)
+
+      expect(response).to have_gitlab_http_status(204)
+      # Check if note is really deleted
+      delete api("/#{parent_type}/#{parent.id}/#{noteable_type}/#{noteable[id_name]}/"\
+                 "discussions/#{note.discussion_id}/notes/#{note.id}", user)
+      expect(response).to have_gitlab_http_status(404)
+    end
+
+    it 'returns a 404 error when note id not found' do
+      delete api("/#{parent_type}/#{parent.id}/#{noteable_type}/#{noteable[id_name]}/"\
+                 "discussions/#{note.discussion_id}/notes/12345", user)
+
+      expect(response).to have_gitlab_http_status(404)
+    end
+
+    it_behaves_like '412 response' do
+      let(:request) do
+        api("/#{parent_type}/#{parent.id}/#{noteable_type}/#{noteable[id_name]}/"\
+            "discussions/#{note.discussion_id}/notes/#{note.id}", user)
+      end
+    end
+  end
+end
--- a/spec/support/shared_examples/requests/api/notes.rb
+++ b/spec/support/shared_examples/requests/api/notes.rb
+shared_examples 'noteable API' do |parent_type, noteable_type, id_name|
+  describe "GET /#{parent_type}/:id/#{noteable_type}/:noteable_id/notes" do
+    context 'sorting' do
+      before do
+        params = { noteable: noteable, author: user }
+        params[:project] = parent if parent.is_a?(Project)
+
+        create_list(:note, 3, params)
+      end
+
+      it 'sorts by created_at in descending order by default' do
+        get api("/#{parent_type}/#{parent.id}/#{noteable_type}/#{noteable[id_name]}/notes", user)
+
+        response_dates = json_response.map { |note| note['created_at'] }
+
+        expect(json_response.length).to eq(4)
+        expect(response_dates).to eq(response_dates.sort.reverse)
+      end
+
+      it 'sorts by ascending order when requested' do
+        get api("/#{parent_type}/#{parent.id}/#{noteable_type}/#{noteable[id_name]}/notes?sort=asc", user)
+
+        response_dates = json_response.map { |note| note['created_at'] }
+
+        expect(json_response.length).to eq(4)
+        expect(response_dates).to eq(response_dates.sort)
+      end
+
+      it 'sorts by updated_at in descending order when requested' do
+        get api("/#{parent_type}/#{parent.id}/#{noteable_type}/#{noteable[id_name]}/notes?order_by=updated_at", user)
+
+        response_dates = json_response.map { |note| note['updated_at'] }
+
+        expect(json_response.length).to eq(4)
+        expect(response_dates).to eq(response_dates.sort.reverse)
+      end
+
+      it 'sorts by updated_at in ascending order when requested' do
+        get api("/#{parent_type}/#{parent.id}/#{noteable_type}/#{noteable[id_name]}/notes?order_by=updated_at&sort=asc", user)
+
+        response_dates = json_response.map { |note| note['updated_at'] }
+
+        expect(json_response.length).to eq(4)
+        expect(response_dates).to eq(response_dates.sort)
+      end
+    end
+
+    it "returns an array of notes" do
+      get api("/#{parent_type}/#{parent.id}/#{noteable_type}/#{noteable[id_name]}/notes", user)
+
+      expect(response).to have_gitlab_http_status(200)
+      expect(response).to include_pagination_headers
+      expect(json_response).to be_an Array
+      expect(json_response.first['body']).to eq(note.note)
+    end
+
+    it "returns a 404 error when noteable id not found" do
+      get api("/#{parent_type}/#{parent.id}/#{noteable_type}/12345/notes", user)
+
+      expect(response).to have_gitlab_http_status(404)
+    end
+
+    it "returns 404 when not authorized" do
+      parent.update!(visibility_level: Gitlab::VisibilityLevel::PRIVATE)
+
+      get api("/#{parent_type}/#{parent.id}/#{noteable_type}/#{noteable[id_name]}/notes", private_user)
+
+      expect(response).to have_gitlab_http_status(404)
+    end
+  end
+
+  describe "GET /#{parent_type}/:id/#{noteable_type}/:noteable_id/notes/:note_id" do
+    it "returns a note by id" do
+      get api("/#{parent_type}/#{parent.id}/#{noteable_type}/#{noteable[id_name]}/notes/#{note.id}", user)
+
+      expect(response).to have_gitlab_http_status(200)
+      expect(json_response['body']).to eq(note.note)
+    end
+
+    it "returns a 404 error if note not found" do
+      get api("/#{parent_type}/#{parent.id}/#{noteable_type}/#{noteable[id_name]}/notes/12345", user)
+
+      expect(response).to have_gitlab_http_status(404)
+    end
+  end
+
+  describe "POST /#{parent_type}/:id/#{noteable_type}/:noteable_id/notes" do
+    it "creates a new note" do
+      post api("/#{parent_type}/#{parent.id}/#{noteable_type}/#{noteable[id_name]}/notes", user), body: 'hi!'
+
+      expect(response).to have_gitlab_http_status(201)
+      expect(json_response['body']).to eq('hi!')
+      expect(json_response['author']['username']).to eq(user.username)
+    end
+
+    it "returns a 400 bad request error if body not given" do
+      post api("/#{parent_type}/#{parent.id}/#{noteable_type}/#{noteable[id_name]}/notes", user)
+
+      expect(response).to have_gitlab_http_status(400)
+    end
+
+    it "returns a 401 unauthorized error if user not authenticated" do
+      post api("/#{parent_type}/#{parent.id}/#{noteable_type}/#{noteable[id_name]}/notes"), body: 'hi!'
+
+      expect(response).to have_gitlab_http_status(401)
+    end
+
+    it "creates an activity event when a note is created" do
+      expect(Event).to receive(:create!)
+
+      post api("/#{parent_type}/#{parent.id}/#{noteable_type}/#{noteable[id_name]}/notes", user), body: 'hi!'
+    end
+
+    context 'when an admin or owner makes the request' do
+      it 'accepts the creation date to be set' do
+        creation_time = 2.weeks.ago
+        post api("/#{parent_type}/#{parent.id}/#{noteable_type}/#{noteable[id_name]}/notes", user),
+          body: 'hi!', created_at: creation_time
+
+        expect(response).to have_gitlab_http_status(201)
+        expect(json_response['body']).to eq('hi!')
+        expect(json_response['author']['username']).to eq(user.username)
+        expect(Time.parse(json_response['created_at'])).to be_like_time(creation_time)
+      end
+    end
+
+    context 'when the user is posting an award emoji on a noteable created by someone else' do
+      it 'creates a new note' do
+        parent.add_developer(private_user)
+        post api("/#{parent_type}/#{parent.id}/#{noteable_type}/#{noteable[id_name]}/notes", private_user), body: ':+1:'
+
+        expect(response).to have_gitlab_http_status(201)
+        expect(json_response['body']).to eq(':+1:')
+      end
+    end
+
+    context 'when the user is posting an award emoji on his/her own noteable' do
+      it 'creates a new note' do
+        post api("/#{parent_type}/#{parent.id}/#{noteable_type}/#{noteable[id_name]}/notes", user), body: ':+1:'
+
+        expect(response).to have_gitlab_http_status(201)
+        expect(json_response['body']).to eq(':+1:')
+      end
+    end
+
+    context 'when user does not have access to read the noteable' do
+      before do
+        parent.update!(visibility_level: Gitlab::VisibilityLevel::PRIVATE)
+      end
+
+      it 'responds with 404' do
+        post api("/#{parent_type}/#{parent.id}/#{noteable_type}/#{noteable[id_name]}/notes", private_user),
+          body: 'Foo'
+
+        expect(response).to have_gitlab_http_status(404)
+      end
+    end
+  end
+
+  describe "PUT /#{parent_type}/:id/#{noteable_type}/:noteable_id/notes/:note_id" do
+    it 'returns modified note' do
+      put api("/#{parent_type}/#{parent.id}/#{noteable_type}/#{noteable[id_name]}/"\
+                "notes/#{note.id}", user), body: 'Hello!'
+
+      expect(response).to have_gitlab_http_status(200)
+      expect(json_response['body']).to eq('Hello!')
+    end
+
+    it 'returns a 404 error when note id not found' do
+      put api("/#{parent_type}/#{parent.id}/#{noteable_type}/#{noteable[id_name]}/notes/12345", user),
+              body: 'Hello!'
+
+      expect(response).to have_gitlab_http_status(404)
+    end
+
+    it 'returns a 400 bad request error if body not given' do
+      put api("/#{parent_type}/#{parent.id}/#{noteable_type}/#{noteable[id_name]}/"\
+                "notes/#{note.id}", user)
+
+      expect(response).to have_gitlab_http_status(400)
+    end
+  end
+
+  describe "DELETE /#{parent_type}/:id/#{noteable_type}/:noteable_id/notes/:note_id" do
+    it 'deletes a note' do
+      delete api("/#{parent_type}/#{parent.id}/#{noteable_type}/#{noteable[id_name]}/"\
+                 "notes/#{note.id}", user)
+
+      expect(response).to have_gitlab_http_status(204)
+      # Check if note is really deleted
+      delete api("/#{parent_type}/#{parent.id}/#{noteable_type}/#{noteable[id_name]}/"\
+                 "notes/#{note.id}", user)
+      expect(response).to have_gitlab_http_status(404)
+    end
+
+    it 'returns a 404 error when note id not found' do
+      delete api("/#{parent_type}/#{parent.id}/#{noteable_type}/#{noteable[id_name]}/notes/12345", user)
+
+      expect(response).to have_gitlab_http_status(404)
+    end
+
+    it_behaves_like '412 response' do
+      let(:request) { api("/#{parent_type}/#{parent.id}/#{noteable_type}/#{noteable[id_name]}/notes/#{note.id}", user) }
+    end
+  end
+end