Add source and target branch filters to merge requests API

app/finders/merge_requests_finder.rb

@@ -17,14 +17,42 @@
 #     sort: string
 #     non_archived: boolean
 #     my_reaction_emoji: string
+#     source_branch: string
+#     target_branch: string
 #
 class MergeRequestsFinder < IssuableFinder
   def klass
     MergeRequest
   end
 
+  def filter_items(_items)
+    items = by_source_branch(super)
+
+    by_target_branch(items)
+  end
+
   private
 
+  def source_branch
+    @source_branch ||= params[:source_branch].presence
+  end
+
+  def by_source_branch(items)
+    return items unless source_branch
+
+    items.where(source_branch: source_branch)
+  end
+
+  def target_branch
+    @target_branch ||= params[:target_branch].presence
+  end
+
+  def by_target_branch(items)
+    return items unless target_branch
+
+    items.where(target_branch: target_branch)
+  end
+
   def item_project_ids(items)
     items&.reorder(nil)&.select(:target_project_id)
   end

changelogs/unreleased/merge-requests-api-filter-by-branch.yml

+---
+title: Add support for filtering by source and target branch to merge requests API
+merge_request:
+author:
+type: added

doc/api/merge_requests.md

@@ -47,6 +47,8 @@ Parameters:
 | `author_id`         | integer  | no       | Returns merge requests created by the given user `id`. Combine with `scope=all` or `scope=assigned-to-me`              |
 | `assignee_id`       | integer  | no       | Returns merge requests assigned to the given user `id`                                                                 |
 | `my_reaction_emoji` | string   | no       | Return merge requests reacted by the authenticated user by the given `emoji` _([Introduced][ce-14016] in GitLab 10.0)_ |
+| `source_branch`     | string   | no       | Return merge requests with the given source branch                                                                     |
+| `target_branch`     | string   | no       | Return merge requests with the given target branch                                                                     |
 | `search`            | string   | no       | Search merge requests against their `title` and `description`                                                          |
 
 ```json
@@ -162,6 +164,8 @@ Parameters:
 | `author_id`         | integer        | no       | Returns merge requests created by the given user `id` _([Introduced][ce-13060] in GitLab 9.5)_                                 |
 | `assignee_id`       | integer        | no       | Returns merge requests assigned to the given user `id` _([Introduced][ce-13060] in GitLab 9.5)_                                |
 | `my_reaction_emoji` | string         | no       | Return merge requests reacted by the authenticated user by the given `emoji` _([Introduced][ce-14016] in GitLab 10.0)_         |
+| `source_branch`     | string   | no       | Return merge requests with the given source branch                                                                     |
+| `target_branch`     | string   | no       | Return merge requests with the given target branch                                                                     |
 | `search`            | string         | no       | Search merge requests against their `title` and `description`                                                                  |
 
 ```json

lib/api/merge_requests.rb

@@ -48,6 +48,8 @@ module API
         optional :scope, type: String, values: %w[created-by-me assigned-to-me all],
                          desc: 'Return merge requests for the given scope: `created-by-me`, `assigned-to-me` or `all`'
         optional :my_reaction_emoji, type: String, desc: 'Return issues reacted by the authenticated user by the given emoji'
+        optional :source_branch, type: String, desc: 'Return merge requests with the given source branch'
+        optional :target_branch, type: String, desc: 'Return merge requests with the given target branch'
         optional :search, type: String, desc: 'Search merge requests for text present in the title or description'
         use :pagination
       end

spec/finders/merge_requests_finder_spec.rb

@@ -18,7 +18,7 @@ describe MergeRequestsFinder do
   let(:project4) { create(:project, :public, group: subgroup) }
 
   let!(:merge_request1) { create(:merge_request, :simple, author: user, source_project: project2, target_project: project1) }
-  let!(:merge_request2) { create(:merge_request, :simple, author: user, source_project: project2, target_project: project1, state: 'closed') }
+  let!(:merge_request2) { create(:merge_request, :conflict, author: user, source_project: project2, target_project: project1, state: 'closed') }
   let!(:merge_request3) { create(:merge_request, :simple, author: user, source_project: project2, target_project: project2) }
   let!(:merge_request4) { create(:merge_request, :simple, author: user, source_project: project3, target_project: project3) }
   let!(:merge_request5) { create(:merge_request, :simple, author: user, source_project: project4, target_project: project4) }
@@ -74,6 +74,22 @@ describe MergeRequestsFinder do
       expect(merge_requests).to contain_exactly(merge_request1)
     end
 
+    it 'filters by source branch' do
+      params = { source_branch: merge_request2.source_branch }
+
+      merge_requests = described_class.new(user, params).execute
+
+      expect(merge_requests).to contain_exactly(merge_request2)
+    end
+
+    it 'filters by target branch' do
+      params = { target_branch: merge_request2.target_branch }
+
+      merge_requests = described_class.new(user, params).execute
+
+      expect(merge_requests).to contain_exactly(merge_request2)
+    end
+
     context 'filtering by group milestone' do
       let!(:group) { create(:group, :public) }
       let(:group_milestone) { create(:milestone, group: group) }

spec/requests/api/merge_requests_spec.rb

@@ -151,6 +151,26 @@ describe API::MergeRequests do
         expect(json_response.first['id']).to eq(merge_request3.id)
       end
 
+      context 'source_branch param' do
+        it 'returns merge requests with the given source branch' do
+          get api('/merge_requests', user), source_branch: merge_request_closed.source_branch, state: 'all'
+
+          expect(json_response.length).to eq(2)
+          expect(json_response.map { |mr| mr['id'] })
+            .to contain_exactly(merge_request_closed.id, merge_request_merged.id)
+        end
+      end
+
+      context 'target_branch param' do
+        it 'returns merge requests with the given target branch' do
+          get api('/merge_requests', user), target_branch: merge_request_closed.target_branch, state: 'all'
+
+          expect(json_response.length).to eq(2)
+          expect(json_response.map { |mr| mr['id'] })
+            .to contain_exactly(merge_request_closed.id, merge_request_merged.id)
+        end
+      end
+
       context 'search params' do
         before do
           merge_request.update(title: 'Search title', description: 'Search description')
@@ -426,6 +446,26 @@ describe API::MergeRequests do
           expect(response_dates).to eq(response_dates.sort)
         end
       end
+
+      context 'source_branch param' do
+        it 'returns merge requests with the given source branch' do
+          get api('/merge_requests', user), source_branch: merge_request_closed.source_branch, state: 'all'
+
+          expect(json_response.length).to eq(2)
+          expect(json_response.map { |mr| mr['id'] })
+            .to contain_exactly(merge_request_closed.id, merge_request_merged.id)
+        end
+      end
+
+      context 'target_branch param' do
+        it 'returns merge requests with the given target branch' do
+          get api('/merge_requests', user), target_branch: merge_request_closed.target_branch, state: 'all'
+
+          expect(json_response.length).to eq(2)
+          expect(json_response.map { |mr| mr['id'] })
+            .to contain_exactly(merge_request_closed.id, merge_request_merged.id)
+        end
+      end
     end
   end