Add an API endpoint to determine the forks of a project

4 files changed, 169 insertions, 4 deletions

diff --git a/changelogs/unreleased/20049-projects-api-forks.yml b/changelogs/unreleased/20049-projects-api-forks.yml
new file mode 100644
index 00000000000..c6470620f57
--- /dev/null
+++ b/changelogs/unreleased/20049-projects-api-forks.yml
@@ -0,0 +1,5 @@
+---
+title: Add an API endpoint to determine the forks of a project
+merge_request:
+author:
+type: added
diff --git a/doc/api/projects.md b/doc/api/projects.md
index 3144220e588..07331d05231 100644
--- a/doc/api/projects.md
+++ b/doc/api/projects.md
@@ -635,6 +635,98 @@ POST /projects/:id/fork
 | `id` | integer/string | yes | The ID or [URL-encoded path of the project](README.md#namespaced-path-encoding) |
 | `namespace` | integer/string | yes | The ID or path of the namespace that the project will be forked to |
 
+## List Forks of a project
+
+>**Note:** This feature was introduced in GitLab 10.1
+
+List the projects accessible to the calling user that have an established, forked relationship with the specified project
+
+```
+GET /projects/:id/forks
+```
+
+| Attribute | Type | Required | Description |
+| --------- | ---- | -------- | ----------- |
+| `id` | integer/string | yes | The ID or [URL-encoded path of the project](README.md#namespaced-path-encoding) |
+| `archived` | boolean | no | Limit by archived status |
+| `visibility` | string | no | Limit by visibility `public`, `internal`, or `private` |
+| `order_by` | string | no | Return projects ordered by `id`, `name`, `path`, `created_at`, `updated_at`, or `last_activity_at` fields. Default is `created_at` |
+| `sort` | string | no | Return projects sorted in `asc` or `desc` order. Default is `desc` |
+| `search` | string | no | Return list of projects matching the search criteria |
+| `simple` | boolean | no | Return only the ID, URL, name, and path of each project |
+| `owned` | boolean | no | Limit by projects owned by the current user |
+| `membership` | boolean | no | Limit by projects that the current user is a member of |
+| `starred` | boolean | no | Limit by projects starred by the current user |
+| `statistics` | boolean | no | Include project statistics |
+| `with_issues_enabled` | boolean | no | Limit by enabled issues feature |
+| `with_merge_requests_enabled` | boolean | no | Limit by enabled merge requests feature |
+
+```bash
+curl --header "PRIVATE-TOKEN: 9koXpg98eAheJpvBs5tK" "https://gitlab.example.com/api/v4/projects/5/forks"
+```
+
+Example responses:
+
+```json
+[
+  {
+    "id": 3,
+    "description": null,
+    "default_branch": "master",
+    "visibility": "internal",
+    "ssh_url_to_repo": "git@example.com:diaspora/diaspora-project-site.git",
+    "http_url_to_repo": "http://example.com/diaspora/diaspora-project-site.git",
+    "web_url": "http://example.com/diaspora/diaspora-project-site",
+    "tag_list": [
+      "example",
+      "disapora project"
+    ],
+    "name": "Diaspora Project Site",
+    "name_with_namespace": "Diaspora / Diaspora Project Site",
+    "path": "diaspora-project-site",
+    "path_with_namespace": "diaspora/diaspora-project-site",
+    "issues_enabled": true,
+    "open_issues_count": 1,
+    "merge_requests_enabled": true,
+    "jobs_enabled": true,
+    "wiki_enabled": true,
+    "snippets_enabled": false,
+    "resolve_outdated_diff_discussions": false,
+    "container_registry_enabled": false,
+    "created_at": "2013-09-30T13:46:02Z",
+    "last_activity_at": "2013-09-30T13:46:02Z",
+    "creator_id": 3,
+    "namespace": {
+      "id": 3,
+      "name": "Diaspora",
+      "path": "diaspora",
+      "kind": "group",
+      "full_path": "diaspora"
+    },
+    "import_status": "none",
+    "archived": true,
+    "avatar_url": "http://example.com/uploads/project/avatar/3/uploads/avatar.png",
+    "shared_runners_enabled": true,
+    "forks_count": 0,
+    "star_count": 1,
+    "public_jobs": true,
+    "shared_with_groups": [],
+    "only_allow_merge_if_pipeline_succeeds": false,
+    "only_allow_merge_if_all_discussions_are_resolved": false,
+    "request_access_enabled": false,
+    "_links": {
+      "self": "http://example.com/api/v4/projects",
+      "issues": "http://example.com/api/v4/projects/1/issues",
+      "merge_requests": "http://example.com/api/v4/projects/1/merge_requests",
+      "repo_branches": "http://example.com/api/v4/projects/1/repository_branches",
+      "labels": "http://example.com/api/v4/projects/1/labels",
+      "events": "http://example.com/api/v4/projects/1/events",
+      "members": "http://example.com/api/v4/projects/1/members"
+    }
+  }
+]
+```
+
 ## Star a project
 
 Stars a given project. Returns status code `304` if the project is already starred.
diff --git a/lib/api/projects.rb b/lib/api/projects.rb
index 7dc19788462..aab7a6c3f93 100644
--- a/lib/api/projects.rb
+++ b/lib/api/projects.rb
@@ -70,8 +70,11 @@ module API
         optional :import_url, type: String, desc: 'URL from which the project is imported'
       end
 
-      def present_projects(options = {})
-        projects = ProjectsFinder.new(current_user: current_user, params: project_finder_params).execute
+      def load_projects
+        ProjectsFinder.new(current_user: current_user, params: project_finder_params).execute
+      end
+
+      def present_projects(projects, options = {})
         projects = reorder_projects(projects)
         projects = projects.with_statistics if params[:statistics]
         projects = projects.with_issues_enabled if params[:with_issues_enabled]
@@ -111,7 +114,7 @@ module API
 
         params[:user] = user
 
-        present_projects
+        present_projects load_projects
       end
     end
 
@@ -124,7 +127,7 @@ module API
         use :statistics_params
       end
       get do
-        present_projects
+        present_projects load_projects
       end
 
       desc 'Create new project' do
@@ -229,6 +232,18 @@ module API
         end
       end
 
+      desc 'List forks of this project' do
+        success Entities::Project
+      end
+      params do
+        use :collection_params
+      end
+      get ':id/forks' do
+        forks = ForkProjectsFinder.new(user_project, params: project_finder_params, current_user: current_user).execute
+
+        present_projects forks
+      end
+
       desc 'Update an existing project' do
         success Entities::Project
       end
diff --git a/spec/requests/api/projects_spec.rb b/spec/requests/api/projects_spec.rb
index 92e7d797cbd..508df990952 100644
--- a/spec/requests/api/projects_spec.rb
+++ b/spec/requests/api/projects_spec.rb
@@ -1181,6 +1181,59 @@ describe API::Projects do
         end
       end
     end
+
+    describe 'GET /projects/:id/forks' do
+      let(:private_fork) { create(:project, :private, :empty_repo) }
+      let(:member) { create(:user) }
+      let(:non_member) { create(:user) }
+
+      before do
+        private_fork.add_developer(member)
+      end
+
+      context 'for a forked project' do
+        before do
+          post api("/projects/#{private_fork.id}/fork/#{project_fork_source.id}", admin)
+          private_fork.reload
+          expect(private_fork.forked_from_project).not_to be_nil
+          expect(private_fork.forked?).to be_truthy
+          project_fork_source.reload
+          expect(project_fork_source.forks.length).to eq(1)
+          expect(project_fork_source.forks).to include(private_fork)
+        end
+
+        context 'for a user that can access the forks' do
+          it 'returns the forks' do
+            get api("/projects/#{project_fork_source.id}/forks", member)
+
+            expect(response).to have_http_status(200)
+            expect(response).to include_pagination_headers
+            expect(json_response.length).to eq(1)
+            expect(json_response[0]['name']).to eq(private_fork.name)
+          end
+        end
+
+        context 'for a user that cannot access the forks' do
+          it 'returns an empty array' do
+            get api("/projects/#{project_fork_source.id}/forks", non_member)
+
+            expect(response).to have_http_status(200)
+            expect(response).to include_pagination_headers
+            expect(json_response.length).to eq(0)
+          end
+        end
+      end
+
+      context 'for a non-forked project' do
+        it 'returns an empty array' do
+          get api("/projects/#{project_fork_source.id}/forks")
+
+          expect(response).to have_http_status(200)
+          expect(response).to include_pagination_headers
+          expect(json_response.length).to eq(0)
+        end
+      end
+    end
   end
 
   describe "POST /projects/:id/share" do