Merge branch 'api-fix-milestone-iid-filter' into 'master'

API: Add iid filter to milestones

This was documented in the API docs but it was never working because the iid filter was never applied to the milestones. The tests were working by accident because the were checking the first element, which was by accident the request element. 

* Closes https://github.com/gitlabhq/gitlabhq/issues/10122

See merge request !3588

CHANGELOG

@@ -23,6 +23,7 @@ v 8.7.0 (unreleased)
   - Add default scope to projects to exclude projects pending deletion
   - Ensure empty recipients are rejected in BuildsEmailService
   - API: Ability to filter milestones by state `active` and `closed` (Robert Schilling)
+  - API: Fix milestone filtering by `iid` (Robert Schilling)
   - Implement 'Groups View' as an option for dashboard preferences !3379 (Elias W.)
   - Better errors handling when creating milestones inside groups
   - Implement 'TODOs View' as an option for dashboard preferences !3379 (Elias W.)

lib/api/milestones.rb

@@ -21,6 +21,7 @@ module API
       #   state (optional) - Return "active" or "closed" milestones
       # Example Request:
       #   GET /projects/:id/milestones
+      #   GET /projects/:id/milestones?iid=42
       #   GET /projects/:id/milestones?state=active
       #   GET /projects/:id/milestones?state=closed
       get ":id/milestones" do
@@ -28,6 +29,7 @@ module API
         milestones = user_project.milestones
         milestones = filter_milestones_state(milestones, params[:state])
+        milestones = filter_by_iid(milestones, params[:iid]) if params[:iid].present?
         present paginate(milestones), with: Entities::Milestone
       end

spec/requests/api/milestones_spec.rb

@@ -50,10 +50,12 @@ describe API::API, api: true  do
     end
     it 'should return a project milestone by iid' do
-      get api("/projects/#{project.id}/milestones?iid=#{milestone.iid}", user)
+      get api("/projects/#{project.id}/milestones?iid=#{closed_milestone.iid}", user)
+
       expect(response.status).to eq 200
-      expect(json_response.first['title']).to eq milestone.title
-      expect(json_response.first['id']).to eq milestone.id
+      expect(json_response.size).to eq(1)
+      expect(json_response.first['title']).to eq closed_milestone.title
+      expect(json_response.first['id']).to eq closed_milestone.id
     end
     it 'should return 401 error if user not authenticated' do