Add GraphQL migration to set epic of an issue

- Add create  EpicIssues::Create migration
- Add docs and update graphQL schema
- Add  mutation specs
- Add changelog file
- Add specs for mutation request

Use epic related_issues to return epic issue type

doc/api/graphql/reference/gitlab_schema.graphql

@@ -2219,6 +2219,61 @@ type Epic implements Noteable {
   webUrl: String!
 }
 
+"""
+Autogenerated input type of EpicAddIssue
+"""
+input EpicAddIssueInput {
+  """
+  A unique identifier for the client performing the mutation.
+  """
+  clientMutationId: String
+
+  """
+  The group the epic to mutate belongs to
+  """
+  groupPath: ID!
+
+  """
+  The iid of the epic to mutate
+  """
+  iid: ID!
+
+  """
+  The iid of the issue to be added
+  """
+  issueIid: String!
+
+  """
+  The project the issue belongs to
+  """
+  projectPath: ID!
+}
+
+"""
+Autogenerated return type of EpicAddIssue
+"""
+type EpicAddIssuePayload {
+  """
+  A unique identifier for the client performing the mutation.
+  """
+  clientMutationId: String
+
+  """
+  The epic after mutation
+  """
+  epic: Epic
+
+  """
+  The epic-issue relation
+  """
+  epicIssue: EpicIssue
+
+  """
+  Reasons why the mutation failed.
+  """
+  errors: [String!]!
+}
+
 """
 The connection type for Epic.
 """
@@ -2689,7 +2744,7 @@ input EpicSetSubscriptionInput {
   clientMutationId: String
 
   """
-  The group the epic to mutate is in
+  The group the epic to mutate belongs to
   """
   groupPath: ID!
 
@@ -4872,6 +4927,7 @@ type Mutation {
   designManagementUpload(input: DesignManagementUploadInput!): DesignManagementUploadPayload
   destroyNote(input: DestroyNoteInput!): DestroyNotePayload
   destroySnippet(input: DestroySnippetInput!): DestroySnippetPayload
+  epicAddIssue(input: EpicAddIssueInput!): EpicAddIssuePayload
   epicSetSubscription(input: EpicSetSubscriptionInput!): EpicSetSubscriptionPayload
   epicTreeReorder(input: EpicTreeReorderInput!): EpicTreeReorderPayload
   issueSetConfidential(input: IssueSetConfidentialInput!): IssueSetConfidentialPayload

doc/api/graphql/reference/gitlab_schema.json

@@ -19402,6 +19402,33 @@
               "isDeprecated": false,
               "deprecationReason": null
             },
+            {
+              "name": "epicAddIssue",
+              "description": null,
+              "args": [
+                {
+                  "name": "input",
+                  "description": null,
+                  "type": {
+                    "kind": "NON_NULL",
+                    "name": null,
+                    "ofType": {
+                      "kind": "INPUT_OBJECT",
+                      "name": "EpicAddIssueInput",
+                      "ofType": null
+                    }
+                  },
+                  "defaultValue": null
+                }
+              ],
+              "type": {
+                "kind": "OBJECT",
+                "name": "EpicAddIssuePayload",
+                "ofType": null
+              },
+              "isDeprecated": false,
+              "deprecationReason": null
+            },
             {
               "name": "epicSetSubscription",
               "description": null,
@@ -25120,7 +25147,7 @@
             },
             {
               "name": "groupPath",
-              "description": "The group the epic to mutate is in",
+              "description": "The group the epic to mutate belongs to",
               "type": {
                 "kind": "NON_NULL",
                 "name": null,
@@ -25161,6 +25188,164 @@
           "enumValues": null,
           "possibleTypes": null
         },
+        {
+          "kind": "OBJECT",
+          "name": "EpicAddIssuePayload",
+          "description": "Autogenerated return type of EpicAddIssue",
+          "fields": [
+            {
+              "name": "clientMutationId",
+              "description": "A unique identifier for the client performing the mutation.",
+              "args": [
+
+              ],
+              "type": {
+                "kind": "SCALAR",
+                "name": "String",
+                "ofType": null
+              },
+              "isDeprecated": false,
+              "deprecationReason": null
+            },
+            {
+              "name": "epic",
+              "description": "The epic after mutation",
+              "args": [
+
+              ],
+              "type": {
+                "kind": "OBJECT",
+                "name": "Epic",
+                "ofType": null
+              },
+              "isDeprecated": false,
+              "deprecationReason": null
+            },
+            {
+              "name": "epicIssue",
+              "description": "The epic-issue relation",
+              "args": [
+
+              ],
+              "type": {
+                "kind": "OBJECT",
+                "name": "EpicIssue",
+                "ofType": null
+              },
+              "isDeprecated": false,
+              "deprecationReason": null
+            },
+            {
+              "name": "errors",
+              "description": "Reasons why the mutation failed.",
+              "args": [
+
+              ],
+              "type": {
+                "kind": "NON_NULL",
+                "name": null,
+                "ofType": {
+                  "kind": "LIST",
+                  "name": null,
+                  "ofType": {
+                    "kind": "NON_NULL",
+                    "name": null,
+                    "ofType": {
+                      "kind": "SCALAR",
+                      "name": "String",
+                      "ofType": null
+                    }
+                  }
+                }
+              },
+              "isDeprecated": false,
+              "deprecationReason": null
+            }
+          ],
+          "inputFields": null,
+          "interfaces": [
+
+          ],
+          "enumValues": null,
+          "possibleTypes": null
+        },
+        {
+          "kind": "INPUT_OBJECT",
+          "name": "EpicAddIssueInput",
+          "description": "Autogenerated input type of EpicAddIssue",
+          "fields": null,
+          "inputFields": [
+            {
+              "name": "iid",
+              "description": "The iid of the epic to mutate",
+              "type": {
+                "kind": "NON_NULL",
+                "name": null,
+                "ofType": {
+                  "kind": "SCALAR",
+                  "name": "ID",
+                  "ofType": null
+                }
+              },
+              "defaultValue": null
+            },
+            {
+              "name": "groupPath",
+              "description": "The group the epic to mutate belongs to",
+              "type": {
+                "kind": "NON_NULL",
+                "name": null,
+                "ofType": {
+                  "kind": "SCALAR",
+                  "name": "ID",
+                  "ofType": null
+                }
+              },
+              "defaultValue": null
+            },
+            {
+              "name": "projectPath",
+              "description": "The project the issue belongs to",
+              "type": {
+                "kind": "NON_NULL",
+                "name": null,
+                "ofType": {
+                  "kind": "SCALAR",
+                  "name": "ID",
+                  "ofType": null
+                }
+              },
+              "defaultValue": null
+            },
+            {
+              "name": "issueIid",
+              "description": "The iid of the issue to be added",
+              "type": {
+                "kind": "NON_NULL",
+                "name": null,
+                "ofType": {
+                  "kind": "SCALAR",
+                  "name": "String",
+                  "ofType": null
+                }
+              },
+              "defaultValue": null
+            },
+            {
+              "name": "clientMutationId",
+              "description": "A unique identifier for the client performing the mutation.",
+              "type": {
+                "kind": "SCALAR",
+                "name": "String",
+                "ofType": null
+              },
+              "defaultValue": null
+            }
+          ],
+          "interfaces": null,
+          "enumValues": null,
+          "possibleTypes": null
+        },
         {
           "kind": "OBJECT",
           "name": "__Schema",

doc/api/graphql/reference/index.md

@@ -346,6 +346,17 @@ Represents an epic.
 | `webPath` | String! | Web path of the epic |
 | `webUrl` | String! | Web URL of the epic |
 
+## EpicAddIssuePayload
+
+Autogenerated return type of EpicAddIssue
+
+| Name  | Type  | Description |
+| ---   |  ---- | ----------  |
+| `clientMutationId` | String | A unique identifier for the client performing the mutation. |
+| `epic` | Epic | The epic after mutation |
+| `epicIssue` | EpicIssue | The epic-issue relation |
+| `errors` | String! => Array | Reasons why the mutation failed. |
+
 ## EpicDescendantCount
 
 Counts of descendent epics.

ee/app/graphql/ee/types/mutation_type.rb

@@ -13,6 +13,7 @@ module EE
         mount_mutation ::Mutations::Epics::Update
         mount_mutation ::Mutations::Epics::Create
         mount_mutation ::Mutations::Epics::SetSubscription
+        mount_mutation ::Mutations::Epics::AddIssue
       end
     end
   end

ee/app/graphql/mutations/epics/add_issue.rb

+# frozen_string_literal: true
+
+module Mutations
+  module Epics
+    class AddIssue < Base
+      include Mutations::ResolvesIssuable
+
+      graphql_name 'EpicAddIssue'
+
+      authorize :admin_epic
+
+      argument :project_path, GraphQL::ID_TYPE,
+               required: true,
+               description: 'The project the issue belongs to'
+
+      argument :issue_iid, GraphQL::STRING_TYPE,
+               required: true,
+               description: 'The iid of the issue to be added'
+
+      field :epic_issue,
+            Types::EpicIssueType,
+            null: true,
+            description: 'The epic-issue relation'
+
+      def resolve(group_path:, iid:, project_path:, issue_iid:)
+        epic = authorized_find!(group_path: group_path, iid: iid)
+        issue = resolve_issuable(type: :issue, parent_path: project_path, iid: issue_iid)
+        service = create_epic_issue(epic, issue)
+        epic_issue = service[:status] == :success ? find_epic_issue(epic, issue) : nil
+
+        {
+          epic_issue: epic_issue,
+          errors: service[:message] || []
+        }
+      end
+
+      private
+
+      def create_epic_issue(epic, issue)
+        ::EpicIssues::CreateService.new(epic, current_user, { target_issuable: issue }).execute
+      end
+
+      def find_epic_issue(epic, issue)
+        Epic.related_issues(ids: epic.id).find_by_id(issue.id)
+      end
+    end
+  end
+end

ee/app/graphql/mutations/epics/base.rb

@@ -11,7 +11,7 @@ module Mutations
 
       argument :group_path, GraphQL::ID_TYPE,
                required: true,
-               description: 'The group the epic to mutate is in'
+               description: 'The group the epic to mutate belongs to'
 
       field :epic,
             Types::EpicType,

ee/changelogs/unreleased/36309-graphql-mutation-for-updating-epic-associated-with-issue-2.yml

+---
+title: Add GraphQL mutation to set the epic of an issue
+merge_request: 25628
+author:
+type: added

ee/spec/graphql/mutations/epics/add_issue_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe Mutations::Epics::AddIssue do
+  let_it_be(:group) { create(:group) }
+  let_it_be(:project) { create(:project, namespace: group) }
+  let_it_be(:epic) { create(:epic, group: group) }
+  let(:user) { issue.author }
+  let(:issue) { create(:issue, project: project) }
+
+  subject(:mutation) { described_class.new(object: group, context: { current_user: user }) }
+
+  describe '#resolve' do
+    subject do
+      mutation.resolve(
+        group_path: group.full_path,
+        iid: epic.iid,
+        issue_iid: issue.iid,
+        project_path: project.full_path
+      )
+    end
+
+    it 'raises an error if the resource is not accessible to the user' do
+      expect { subject }.to raise_error(Gitlab::Graphql::Errors::ResourceNotAvailable)
+    end
+
+    context 'when the user can update the epic' do
+      before do
+        stub_licensed_features(epics: true)
+        group.add_developer(user)
+      end
+
+      it 'adds the issue to the epic' do
+        expect(subject[:epic_issue]).to eq(issue)
+        expect(subject[:epic_issue].epic).to eq(epic)
+        expect(issue.reload.epic).to eq(epic)
+        expect(subject[:errors]).to be_empty
+      end
+
+      it 'returns error if the issue is already assigned to the epic' do
+        issue.update!(epic: epic)
+
+        expect(subject[:errors]).to eq('Issue(s) already assigned')
+      end
+
+      it 'returns error if issue is not found' do
+        issue.update!(project: create(:project))
+
+        expect(subject[:errors]).to eq('No Issue found for given params')
+      end
+    end
+  end
+end

ee/spec/requests/api/graphql/mutations/epics/add_issue_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe 'Add an issue to an Epic' do
+  include GraphqlHelpers
+
+  let_it_be(:current_user) { create(:user) }
+  let_it_be(:group) { create(:group) }
+  let_it_be(:project) { create(:project, namespace: group) }
+  let(:epic) { create(:epic, group: group) }
+  let(:issue) { create(:issue, project: project) }
+
+  let(:mutation) do
+    params = { group_path: group.full_path, iid: epic.iid.to_s, issue_iid: issue.iid.to_s, project_path: project.full_path }
+
+    graphql_mutation(:epic_add_issue, params)
+  end
+
+  shared_examples 'mutation without access' do
+    it_behaves_like 'a mutation that returns top-level errors',
+      errors: ['The resource that you are attempting to access does not exist '\
+        'or you don\'t have permission to perform this action']
+
+    it 'does not add issue to the epic' do
+      post_graphql_mutation(mutation, current_user: current_user)
+
+      expect(issue.epic).to be_nil
+    end
+  end
+
+  context 'when epics feature is disabled' do
+    it_behaves_like 'mutation without access'
+  end
+
+  context 'when epics feature is enabled' do
+    before do
+      stub_licensed_features(epics: true)
+    end
+
+    context 'when the user is a group member' do
+      before do
+        group.add_developer(current_user)
+      end
+
+      it 'adds the issue to the epic' do
+        post_graphql_mutation(mutation, current_user: current_user)
+        response = graphql_mutation_response(:epic_add_issue)
+
+        expect(response['errors']).to be_empty
+        expect(response['epicIssue']['iid']).to eq(issue.iid.to_s)
+        expect(response['epicIssue']['epic']['iid']).to eq(epic.iid.to_s)
+        expect(issue.epic).to eq(epic)
+      end
+    end
+
+    context 'when the user is not a group member' do
+      it_behaves_like 'mutation without access'
+    end
+  end
+end