Modify MergeRequestsFinder to allow filtering by commit

app/controllers/projects/commit_controller.rb

@@ -65,7 +65,11 @@ class Projects::CommitController < Projects::ApplicationController
   # rubocop: enable CodeReuse/ActiveRecord
 
   def merge_requests
-    @merge_requests = @commit.merge_requests.map do |mr|
+    @merge_requests = MergeRequestsFinder.new(
+      current_user,
+      project_id: @project.id,
+      commit_sha: @commit.sha
+    ).execute.map do |mr|
       { iid: mr.iid, path: merge_request_path(mr), title: mr.title }
     end
 

app/finders/merge_requests_finder.rb

@@ -36,13 +36,20 @@ class MergeRequestsFinder < IssuableFinder
   end
 
   def filter_items(_items)
-    items = by_source_branch(super)
+    items = by_commit(super)
+    items = by_source_branch(items)
     items = by_wip(items)
     by_target_branch(items)
   end
 
   private
 
+  def by_commit(items)
+    return items unless params[:commit_sha].presence
+
+    items.by_commit_sha(params[:commit_sha])
+  end
+
   def source_branch
     @source_branch ||= params[:source_branch].presence
   end

lib/api/commits.rb

@@ -323,7 +323,13 @@ module API
         commit = user_project.commit(params[:sha])
         not_found! 'Commit' unless commit
 
-        present paginate(commit.merge_requests), with: Entities::MergeRequestBasic
+        commit_merge_requests = MergeRequestsFinder.new(
+          current_user,
+          project_id: user_project.id,
+          commit_sha: commit.sha
+        ).execute
+
+        present paginate(commit_merge_requests), with: Entities::MergeRequestBasic
       end
     end
   end

spec/finders/merge_requests_finder_spec.rb

@@ -31,7 +31,7 @@ describe MergeRequestsFinder do
       p
     end
   end
-  let(:project4) { create_project_without_n_plus_1(group: subgroup) }
+  let(:project4) { create_project_without_n_plus_1(:repository, group: subgroup) }
   let(:project5) { create_project_without_n_plus_1(group: subgroup) }
   let(:project6) { create_project_without_n_plus_1(group: subgroup) }
 
@@ -68,6 +68,15 @@ describe MergeRequestsFinder do
       expect(merge_requests.size).to eq(2)
     end
 
+    it 'filters by commit sha' do
+      merge_requests = described_class.new(
+        user,
+        commit_sha: merge_request5.merge_request_diff.last_commit_sha
+      ).execute
+
+      expect(merge_requests).to contain_exactly(merge_request5)
+    end
+
     context 'filtering by group' do
       it 'includes all merge requests when user has access' do
         params = { group_id: group.id }
@@ -269,6 +278,21 @@ describe MergeRequestsFinder do
         expect(merge_requests).to contain_exactly(old_merge_request, new_merge_request)
       end
     end
+
+    context 'when project restricts merge requests' do
+      let(:non_member) { create(:user) }
+      let(:project) { create(:project, :repository, :public, :merge_requests_private) }
+      let!(:merge_request) { create(:merge_request, source_project: project) }
+
+      it "returns nothing to to non members" do
+        merge_requests = described_class.new(
+          non_member,
+          project_id: project.id
+        ).execute
+
+        expect(merge_requests).to be_empty
+      end
+    end
   end
 
   describe '#row_count', :request_store do