Add topic param to projects api

changelogs/unreleased/dz-api-filter-projects-by-topic.yml

+---
+title: Search projects by topic via API
+merge_request: 59900
+author:
+type: added

doc/api/projects.md

@@ -59,6 +59,7 @@ GET /projects
 | `sort`                                     | string   | **{dotted-circle}** No | Return projects sorted in `asc` or `desc` order. Default is `desc`. |
 | `starred`                                  | boolean  | **{dotted-circle}** No | Limit by projects starred by the current user. |
 | `statistics`                               | boolean  | **{dotted-circle}** No | Include project statistics. |
+| `topic`                                    | string   | **{dotted-circle}** No | Comma-separated topic names. Limit results to projects that match all of given topics. See `tag_list` attribute. |
 | `visibility`                               | string   | **{dotted-circle}** No | Limit by visibility `public`, `internal`, or `private`. |
 | `wiki_checksum_failed` **(PREMIUM)**       | boolean  | **{dotted-circle}** No | Limit projects where the wiki checksum calculation has failed ([Introduced](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/6137) in [GitLab Premium](https://about.gitlab.com/pricing/) 11.2). |
 | `with_custom_attributes`                   | boolean  | **{dotted-circle}** No | Include [custom attributes](custom_attributes.md) in response. _(admins only)_ |

lib/api/helpers.rb

@@ -592,18 +592,26 @@ module API
 
     def project_finder_params_ce
       finder_params = project_finder_params_visibility_ce
+
+      finder_params.merge!(
+        params
+          .slice(:search,
+                 :custom_attributes,
+                 :last_activity_after,
+                 :last_activity_before,
+                 :repository_storage)
+          .symbolize_keys
+          .compact
+      )
+
       finder_params[:with_issues_enabled] = true if params[:with_issues_enabled].present?
       finder_params[:with_merge_requests_enabled] = true if params[:with_merge_requests_enabled].present?
       finder_params[:without_deleted] = true
-      finder_params[:search] = params[:search] if params[:search]
       finder_params[:search_namespaces] = true if params[:search_namespaces].present?
       finder_params[:user] = params.delete(:user) if params[:user]
-      finder_params[:custom_attributes] = params[:custom_attributes] if params[:custom_attributes]
       finder_params[:id_after] = sanitize_id_param(params[:id_after]) if params[:id_after]
       finder_params[:id_before] = sanitize_id_param(params[:id_before]) if params[:id_before]
-      finder_params[:last_activity_after] = params[:last_activity_after] if params[:last_activity_after]
-      finder_params[:last_activity_before] = params[:last_activity_before] if params[:last_activity_before]
-      finder_params[:repository_storage] = params[:repository_storage] if params[:repository_storage]
+      finder_params[:tag] = params[:topic] if params[:topic].present?
       finder_params
     end
 

lib/api/projects.rb

@@ -117,6 +117,7 @@ module API
         optional :last_activity_after, type: DateTime, desc: 'Limit results to projects with last_activity after specified time. Format: ISO 8601 YYYY-MM-DDTHH:MM:SSZ'
         optional :last_activity_before, type: DateTime, desc: 'Limit results to projects with last_activity before specified time. Format: ISO 8601 YYYY-MM-DDTHH:MM:SSZ'
         optional :repository_storage, type: String, desc: 'Which storage shard the repository is on. Available only to admins'
+        optional :topic, type: Array[String], coerce_with: ::API::Validations::Types::CommaSeparatedToArray.coerce, desc: 'Comma-separated list of topics. Limit results to projects having all topics'
 
         use :optional_filter_params_ee
       end

spec/requests/api/projects_spec.rb

@@ -223,6 +223,52 @@ RSpec.describe API::Projects do
         expect(json_response.find { |hash| hash['id'] == project.id }.keys).not_to include('open_issues_count')
       end
 
+      context 'filter by topic (column tag_list)' do
+        before do
+          project.update!(tag_list: %w(ruby javascript))
+        end
+
+        it 'returns no projects' do
+          get api('/projects', user), params: { topic: 'foo' }
+
+          expect(response).to have_gitlab_http_status(:ok)
+          expect(response).to include_pagination_headers
+          expect(json_response).to be_empty
+        end
+
+        it 'returns matching project for a single topic' do
+          get api('/projects', user), params: { topic: 'ruby' }
+
+          expect(response).to have_gitlab_http_status(:ok)
+          expect(response).to include_pagination_headers
+          expect(json_response).to contain_exactly a_hash_including('id' => project.id)
+        end
+
+        it 'returns matching project for multiple topics' do
+          get api('/projects', user), params: { topic: 'ruby, javascript' }
+
+          expect(response).to have_gitlab_http_status(:ok)
+          expect(response).to include_pagination_headers
+          expect(json_response).to contain_exactly a_hash_including('id' => project.id)
+        end
+
+        it 'returns no projects if project match only some topic' do
+          get api('/projects', user), params: { topic: 'ruby, foo' }
+
+          expect(response).to have_gitlab_http_status(:ok)
+          expect(response).to include_pagination_headers
+          expect(json_response).to be_empty
+        end
+
+        it 'ignores topic if it is empty' do
+          get api('/projects', user), params: { topic: '' }
+
+          expect(response).to have_gitlab_http_status(:ok)
+          expect(response).to include_pagination_headers
+          expect(json_response).to be_present
+        end
+      end
+
       context 'and with_issues_enabled=true' do
         it 'only returns projects with issues enabled' do
           project.project_feature.update_attribute(:issues_access_level, ProjectFeature::DISABLED)