Expose project statistics on single requests via the API

+ The statistics parameter was already accepted
* This commit ensure that it is respected for GET /projects/:id endpoint
+ Add documentation of the parameter and update the example response for stats

changelogs/unreleased/31544-size-of-project-from-api.yml

+---
+title: Expose project statistics on single requests via the API
+merge_request:
+author:

doc/api/projects.md

@@ -185,6 +185,7 @@ Parameters:
 | Attribute | Type | Required | Description |
 | --------- | ---- | -------- | ----------- |
 | `id` | integer/string | yes | The ID or [URL-encoded path of the project](README.md#namespaced-path-encoding) |
+| `statistics` | boolean | no | Include project statistics |
 ```json
 {
@@ -256,7 +257,14 @@ Parameters:
   ],
   "only_allow_merge_if_pipeline_succeeds": false,
   "only_allow_merge_if_all_discussions_are_resolved": false,
-  "request_access_enabled": false
+  "request_access_enabled": false,
+  "statistics": {
+    "commit_count": 37,
+    "storage_size": 1038090,
+    "repository_size": 1038090,
+    "lfs_objects_size": 0,
+    "job_artifacts_size": 0
+  }
 }
 ```

lib/api/projects.rb

@@ -26,6 +26,10 @@ module API
       params :optional_params do
         use :optional_params_ce
       end
+
+      params :statistics_params do
+        optional :statistics, type: Boolean, default: false, desc: 'Include project statistics'
+      end
     end
     resource :projects do
@@ -56,10 +60,6 @@ module API
           optional :membership, type: Boolean, default: false, desc: 'Limit by projects that the current user is a member of'
         end
-        params :statistics_params do
-          optional :statistics, type: Boolean, default: false, desc: 'Include project statistics'
-        end
-
         params :create_params do
           optional :namespace_id, type: Integer, desc: 'Namespace ID for the new project. Default to the user namespace.'
           optional :import_url, type: String, desc: 'URL from which the project is imported'
@@ -85,6 +85,7 @@ module API
       end
       params do
         use :collection_params
+        use :statistics_params
       end
       get do
         entity = current_user ? Entities::ProjectWithAccess : Entities::BasicProjectDetails
@@ -151,10 +152,13 @@ module API
       desc 'Get a single project' do
         success Entities::ProjectWithAccess
       end
+      params do
+        use :statistics_params
+      end
       get ":id" do
         entity = current_user ? Entities::ProjectWithAccess : Entities::BasicProjectDetails
         present user_project, with: entity, current_user: current_user,
-                              user_can_admin_project: can?(current_user, :admin_project, user_project)
+                              user_can_admin_project: can?(current_user, :admin_project, user_project), statistics: params[:statistics]
       end
       desc 'Get events for a single project' do

spec/requests/api/projects_spec.rb

@@ -665,6 +665,20 @@ describe API::Projects do
         })
       end
+      it "does not include statistics by default" do
+        get api("/projects/#{project.id}", user)
+
+        expect(response).to have_http_status(200)
+        expect(json_response).not_to include 'statistics'
+      end
+
+      it "includes statistics if requested" do
+        get api("/projects/#{project.id}", user), statistics: true
+
+        expect(response).to have_http_status(200)
+        expect(json_response).to include 'statistics'
+      end
+
       describe 'permissions' do
         context 'all projects' do
           before { project.team << [user, :master] }