Enable filtering milestones by search criteria in the API

- Also remove a redundant test

changelogs/unreleased/28807-search-for-milestone-by-title-in-rest-api.yml

+---
+title: Enable filtering milestones by search criteria in the API
+merge_request: 9606
+author:

doc/api/milestones.md

@@ -10,6 +10,7 @@ GET /projects/:id/milestones?iid=42
 GET /projects/:id/milestones?iid[]=42&iid[]=43
 GET /projects/:id/milestones?state=active
 GET /projects/:id/milestones?state=closed
+GET /projects/:id/milestones?search=version
 ```
 
 Parameters:
@@ -18,7 +19,8 @@ Parameters:
 | --------- | ---- | -------- | ----------- |
 | `id` | integer | yes | The ID of a project |
 | `iid` | Array[integer] | optional | Return only the milestone having the given `iid` |
-| `state` | string | optional | Return  only `active` or `closed` milestones` |
+| `state` | string | optional | Return only `active` or `closed` milestones` |
+| `search` | string | optional | Return only milestones with a title or description matching the provided string |
 
 ```bash
 curl --header "PRIVATE-TOKEN: 9koXpg98eAheJpvBs5tK" https://gitlab.example.com/api/v3/projects/5/milestones
@@ -115,4 +117,4 @@ GET /projects/:id/milestones/:milestone_id/merge_requests
 Parameters:
 
 - `id` (required) - The ID of a project
-- `milestone_id` (required) - The ID of a project milestone
+- `milestone_id` (required) - The ID of a project milestone
\ No newline at end of file

lib/api/helpers.rb

@@ -164,6 +164,10 @@ module API
       items.where(iid: iid)
     end
 
+    def filter_by_search(items, text)
+      items.search(text)
+    end
+
     # error helpers
 
     def forbidden!(reason = nil)

lib/api/milestones.rb

@@ -31,6 +31,7 @@ module API
         optional :state, type: String, values: %w[active closed all], default: 'all',
                          desc: 'Return "active", "closed", or "all" milestones'
         optional :iid, type: Array[Integer], desc: 'The IID of the milestone'
+        optional :search, type: String, desc: 'The search criteria for the title or description of the milestone'
         use :pagination
       end
       get ":id/milestones" do
@@ -39,6 +40,7 @@ module API
         milestones = user_project.milestones
         milestones = filter_milestones_state(milestones, params[:state])
         milestones = filter_by_iid(milestones, params[:iid]) if params[:iid].present?
+        milestones = filter_by_search(milestones, params[:search]) if params[:search]
 
         present paginate(milestones), with: Entities::Milestone
       end

spec/requests/api/milestones_spec.rb

@@ -4,8 +4,8 @@ describe API::Milestones, api: true  do
   include ApiHelpers
   let(:user) { create(:user) }
   let!(:project) { create(:empty_project, namespace: user.namespace ) }
-  let!(:closed_milestone) { create(:closed_milestone, project: project) }
-  let!(:milestone) { create(:milestone, project: project) }
+  let!(:closed_milestone) { create(:closed_milestone, project: project, title: 'version1', description: 'closed milestone') }
+  let!(:milestone) { create(:milestone, project: project, title: 'version2', description: 'open milestone') }
 
   before { project.team << [user, :developer] }
 
@@ -60,17 +60,28 @@ describe API::Milestones, api: true  do
       get api("/projects/#{project.id}/milestones", user), iid: [milestone.iid, closed_milestone.iid]
 
       expect(response).to have_http_status(200)
+      expect(response).to include_pagination_headers
       expect(json_response.size).to eq(2)
       expect(json_response.first['title']).to eq milestone.title
       expect(json_response.first['id']).to eq milestone.id
     end
 
-    it 'returns a project milestone by iid array' do
-      get api("/projects/#{project.id}/milestones", user), iid: [milestone.iid, closed_milestone.iid]
+    it 'returns a project milestone by searching for title' do
+      get api("/projects/#{project.id}/milestones", user), search: 'version2'
 
       expect(response).to have_http_status(200)
       expect(response).to include_pagination_headers
-      expect(json_response.size).to eq(2)
+      expect(json_response.size).to eq(1)
+      expect(json_response.first['title']).to eq milestone.title
+      expect(json_response.first['id']).to eq milestone.id
+    end
+
+    it 'returns a project milestones by searching for description' do
+      get api("/projects/#{project.id}/milestones", user), search: 'open'
+
+      expect(response).to have_http_status(200)
+      expect(response).to include_pagination_headers
+      expect(json_response.size).to eq(1)
       expect(json_response.first['title']).to eq milestone.title
       expect(json_response.first['id']).to eq milestone.id
     end