Include parent_iid and parent link in epic responses

Fixes https://gitlab.com/gitlab-org/gitlab/-/issues/347527

Changelog: added
EE: true

doc/api/epics.md

@@ -49,6 +49,8 @@ NOTE:
 
 ## List epics for a group
 
+> `parent_iid` and `_links[parent]` in response were [introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/347527) in GitLab 14.6.
+
 Gets all epics of the requested group and its subgroups.
 
 ```plaintext
@@ -89,6 +91,7 @@ Example response:
   "iid": 4,
   "group_id": 7,
   "parent_id": 23,
+  "parent_iid": 3,
   "title": "Accusamus iste et ullam ratione voluptatem omnis debitis dolor est.",
   "description": "Molestias dolorem eos vitae expedita impedit necessitatibus quo voluptatum.",
   "state": "opened",
@@ -128,7 +131,8 @@ Example response:
   "_links":{
       "self": "http://gitlab.example.com/api/v4/groups/7/epics/4",
       "epic_issues": "http://gitlab.example.com/api/v4/groups/7/epics/4/issues",
-      "group":"http://gitlab.example.com/api/v4/groups/7"
+      "group":"http://gitlab.example.com/api/v4/groups/7",
+      "parent":"http://gitlab.example.com/api/v4/groups/7/epics/3"
   }
   },
   {
@@ -136,6 +140,7 @@ Example response:
   "iid": 35,
   "group_id": 17,
   "parent_id": 19,
+  "parent_iid": 1,
   "title": "Accusamus iste et ullam ratione voluptatem omnis debitis dolor est.",
   "description": "Molestias dolorem eos vitae expedita impedit necessitatibus quo voluptatum.",
   "state": "opened",
@@ -174,7 +179,8 @@ Example response:
   "_links":{
       "self": "http://gitlab.example.com/api/v4/groups/17/epics/35",
       "epic_issues": "http://gitlab.example.com/api/v4/groups/17/epics/35/issues",
-      "group":"http://gitlab.example.com/api/v4/groups/17"
+      "group":"http://gitlab.example.com/api/v4/groups/17",
+      "parent":"http://gitlab.example.com/api/v4/groups/17/epics/1"
   }
   }
 ]
@@ -182,6 +188,8 @@ Example response:
 
 ## Single epic
 
+> `parent_iid` and `_links[parent]` in response were [introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/347527) in GitLab 14.6.
+
 Gets a single epic
 
 ```plaintext
@@ -204,6 +212,8 @@ Example response:
   "id": 30,
   "iid": 5,
   "group_id": 7,
+  "parent_id": null,
+  "parent_iid": null,
   "title": "Ea cupiditate dolores ut vero consequatur quasi veniam voluptatem et non.",
   "description": "Molestias dolorem eos vitae expedita impedit necessitatibus quo voluptatum.",
   "state": "opened",
@@ -243,13 +253,16 @@ Example response:
   "_links":{
       "self": "http://gitlab.example.com/api/v4/groups/7/epics/5",
       "epic_issues": "http://gitlab.example.com/api/v4/groups/7/epics/5/issues",
-      "group":"http://gitlab.example.com/api/v4/groups/7"
+      "group":"http://gitlab.example.com/api/v4/groups/7",
+      "parent": null
   }
 }
 ```
 
 ## New epic
 
+> `parent_iid` and `_links[parent]` in response were [introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/347527) in GitLab 14.6.
+
 Creates a new epic.
 
 NOTE:
@@ -276,7 +289,7 @@ POST /groups/:id/epics
 | `parent_id`         | integer/string   | no         | The ID of a parent epic (in GitLab 11.11 and later) |
 
 ```shell
-curl --request POST --header "PRIVATE-TOKEN: <your_access_token>" "https://gitlab.example.com/api/v4/groups/1/epics?title=Epic&description=Epic%20description"
+curl --request POST --header "PRIVATE-TOKEN: <your_access_token>" "https://gitlab.example.com/api/v4/groups/1/epics?title=Epic&description=Epic%20description&parent_id=29"
 ```
 
 Example response:
@@ -286,6 +299,8 @@ Example response:
   "id": 33,
   "iid": 6,
   "group_id": 7,
+  "parent_id": 29,
+  "parent_iid": 4,
   "title": "Epic",
   "description": "Epic description",
   "state": "opened",
@@ -325,13 +340,16 @@ Example response:
   "_links":{
     "self": "http://gitlab.example.com/api/v4/groups/7/epics/6",
     "epic_issues": "http://gitlab.example.com/api/v4/groups/7/epics/6/issues",
-    "group":"http://gitlab.example.com/api/v4/groups/7"
+    "group":"http://gitlab.example.com/api/v4/groups/7",
+    "parent": "http://gitlab.example.com/api/v4/groups/7/epics/4"
   }
 }
 ```
 
 ## Update epic
 
+> `parent_iid` and `_links[parent]` in response were [introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/347527) in GitLab 14.6.
+
 Updates an epic.
 
 NOTE:
@@ -371,6 +389,8 @@ Example response:
   "id": 33,
   "iid": 6,
   "group_id": 7,
+  "parent_id": null,
+  "parent_iid": null,
   "title": "New Title",
   "description": "Epic description",
   "state": "opened",

ee/app/models/ee/epic.rb

@@ -137,7 +137,7 @@ module EE
         where(boards_epic_board_positions: { relative_position: nil })
       end
 
-      scope :with_api_entity_associations, -> { preload(:author, :labels, group: :route) }
+      scope :with_api_entity_associations, -> { preload(:author, :labels, :parent, group: :route) }
       scope :start_date_inherited, -> { where(start_date_is_fixed: [nil, false]) }
       scope :due_date_inherited, -> { where(due_date_is_fixed: [nil, false]) }
 

ee/lib/ee/api/entities/epic.rb

@@ -12,6 +12,9 @@ module EE
         expose :iid
         expose :group_id
         expose :parent_id
+        expose :parent_iid do |epic|
+          epic.parent.iid if epic.has_parent?
+        end
         expose :title
         expose :description
         expose :confidential
@@ -92,6 +95,10 @@ module EE
           expose :group do |epic|
             expose_url(api_v4_groups_path(id: epic.group_id))
           end
+
+          expose :parent do |epic|
+            expose_url(api_v4_groups_epics_path(id: epic.parent.group_id, epic_iid: epic.parent.iid)) if epic.has_parent?
+          end
         end
       end
     end

ee/spec/fixtures/api/schemas/public_api/v4/epic.json

@@ -5,6 +5,7 @@
     "iid": { "type": "integer" },
     "group_id": { "type": "integer" },
     "parent_id": { "type": ["integer", "null"] },
+    "parent_iid": { "type": ["integer", "null"] },
     "title": { "type": "string" },
     "description": { "type": ["string", "null"] },
     "confidential": { "type": "boolean" },
@@ -58,6 +59,7 @@
         "self": { "type": "uri" },
         "epic_issues": { "type": "uri" },
         "group": { "type": "uri" },
+        "parent": { "type": "uri" },
         "additionalProperties": false
       }
     }

ee/spec/requests/api/epics_spec.rb

@@ -96,8 +96,8 @@ RSpec.describe API::Epics do
         pat = create(:personal_access_token, user: user)
         subgroup_1 = create(:group, parent: group)
         subgroup_2 = create(:group, parent: subgroup_1)
-        create(:epic, group: subgroup_1)
-        create(:epic, group: subgroup_2)
+        epic1 = create(:epic, group: subgroup_1)
+        epic2 = create(:epic, group: subgroup_2, parent_id: epic.id)
 
         control = ActiveRecord::QueryRecorder.new(skip_cached: false) do
           get api(url, personal_access_token: pat), params: params
@@ -105,6 +105,8 @@ RSpec.describe API::Epics do
 
         label_2 = create(:label)
         create_list(:labeled_epic, 2, group: group, labels: [label_2])
+        create_list(:epic, 2, group: subgroup_1, parent_id: epic1.id)
+        create_list(:epic, 2, group: subgroup_2, parent_id: epic2.id)
 
         expect { get api(url, personal_access_token: pat), params: params }.not_to exceed_all_query_limit(control)
         expect(response).to have_gitlab_http_status(:ok)
@@ -156,6 +158,24 @@ RSpec.describe API::Epics do
       end
     end
 
+    context 'with a parent epic' do
+      let!(:epic) { create(:epic, group: group) }
+      let!(:epic2) { create(:epic, group: group, parent_id: epic.id) }
+
+      before do
+        stub_licensed_features(epics: true)
+      end
+
+      it 'returns parent_id and parent_iid' do
+        get api(url, user)
+
+        epics = json_response
+
+        expect(epics.map { |e| e["parent_id"] }).to match_array([nil, epic.id])
+        expect(epics.map { |e| e["parent_iid"] }).to match_array([nil, epic.iid])
+      end
+    end
+
     context 'with multiple epics' do
       let(:user2) { create(:user) }
       let!(:epic) do
@@ -569,6 +589,20 @@ RSpec.describe API::Epics do
         expect(links['self']).to end_with("/api/v4/groups/#{epic.group.id}/epics/#{epic.iid}")
         expect(links['epic_issues']).to end_with("/api/v4/groups/#{epic.group.id}/epics/#{epic.iid}/issues")
         expect(links['group']).to end_with("/api/v4/groups/#{epic.group.id}")
+        expect(links['parent']).to eq(nil)
+      end
+
+      context 'with a parent epic' do
+        let!(:epic2) { create(:epic, group: group, parent_id: epic.id) }
+        let(:url) { "/groups/#{group.path}/epics/#{epic2.iid}" }
+
+        it 'exposes parent link' do
+          get api(url)
+
+          links = json_response['_links']
+
+          expect(links['parent']).to end_with("/api/v4/groups/#{epic.group.id}/epics/#{epic.iid}")
+        end
       end
 
       it_behaves_like 'can admin epics'
@@ -619,6 +653,14 @@ RSpec.describe API::Epics do
           expect(response).to match_response_schema('public_api/v4/epic', dir: 'ee')
         end
 
+        it 'exposes parent information' do
+          post api(url, user), params: params
+
+          expect(json_response['parent_id']).to eq(parent_epic.id)
+          expect(json_response['parent_iid']).to eq(parent_epic.iid)
+          expect(json_response['_links']['parent']).to end_with("/api/v4/groups/#{parent_epic.group.id}/epics/#{parent_epic.iid}")
+        end
+
         it 'creates a new epic' do
           epic = Epic.last