Add projects parameter to IssuableFinder

app/finders/issuable_finder.rb

@@ -193,15 +193,30 @@ class IssuableFinder
     projects =
       if current_user && params[:authorized_only].presence && !current_user_related?
         current_user.authorized_projects(min_access_level)
-      elsif group
-        find_group_projects
       else
-        Project.public_or_visible_to_user(current_user, min_access_level)
+        projects_public_or_visible_to_user
       end
 
     @projects = projects.with_feature_available_for_user(klass, current_user).reorder(nil) # rubocop: disable CodeReuse/ActiveRecord
   end
 
+  def projects_public_or_visible_to_user
+    projects =
+      if group
+        if params[:projects]
+          find_group_projects.id_in(params[:projects])
+        else
+          find_group_projects
+        end
+      elsif params[:projects]
+        Project.id_in(params[:projects])
+      else
+        Project
+      end
+
+    projects.public_or_visible_to_user(current_user, min_access_level)
+  end
+
   def find_group_projects
     return Project.none unless group
 
@@ -209,7 +224,7 @@ class IssuableFinder
       Project.where(namespace_id: group.self_and_descendants) # rubocop: disable CodeReuse/ActiveRecord
     else
       group.projects
-    end.public_or_visible_to_user(current_user, min_access_level)
+    end
   end
 
   def search

spec/finders/issues_finder_spec.rb

@@ -42,6 +42,24 @@ describe IssuesFinder do
         end
       end
 
+      context 'filtering by projects' do
+        context 'when projects are passed in a list of ids' do
+          let(:params) { { projects: [project1.id] } }
+
+          it 'returns the issue belonging to the projects' do
+            expect(issues).to contain_exactly(issue1)
+          end
+        end
+
+        context 'when projects are passed in a subquery' do
+          let(:params) { { projects: Project.id_in(project1.id) } }
+
+          it 'returns the issue belonging to the projects' do
+            expect(issues).to contain_exactly(issue1)
+          end
+        end
+      end
+
       context 'filtering by group_id' do
         let(:params) { { group_id: group.id } }
 
@@ -49,6 +67,30 @@ describe IssuesFinder do
           it 'returns all group issues' do
             expect(issues).to contain_exactly(issue1)
           end
+
+          context 'when projects outside the group are passed' do
+            let(:params) { { group_id: group.id, projects: [project2.id] } }
+
+            it 'returns no issues' do
+              expect(issues).to be_empty
+            end
+          end
+
+          context 'when projects of the group are passed' do
+            let(:params) { { group_id: group.id, projects: [project1.id] } }
+
+            it 'returns the issue within the group and projects' do
+              expect(issues).to contain_exactly(issue1)
+            end
+          end
+
+          context 'when projects of the group are passed as a subquery' do
+            let(:params) { { group_id: group.id, projects: Project.id_in(project1.id) } }
+
+            it 'returns the issue within the group and projects' do
+              expect(issues).to contain_exactly(issue1)
+            end
+          end
         end
 
         context 'when include_subgroup param is true' do
@@ -59,6 +101,14 @@ describe IssuesFinder do
           it 'returns all group and subgroup issues' do
             expect(issues).to contain_exactly(issue1, issue4)
           end
+
+          context 'when mixed projects are passed' do
+            let(:params) { { group_id: group.id, projects: [project2.id, project3.id] } }
+
+            it 'returns the issue within the group and projects' do
+              expect(issues).to contain_exactly(issue4)
+            end
+          end
         end
       end
 

spec/finders/merge_requests_finder_spec.rb

@@ -13,7 +13,7 @@ describe MergeRequestsFinder do
         expect(merge_requests).to contain_exactly(merge_request1, merge_request4, merge_request5)
       end
 
-      it 'filters by project' do
+      it 'filters by project_id' do
         params = { project_id: project1.id, scope: 'authored', state: 'opened' }
 
         merge_requests = described_class.new(user, params).execute
@@ -21,6 +21,14 @@ describe MergeRequestsFinder do
         expect(merge_requests).to contain_exactly(merge_request1)
       end
 
+      it 'filters by projects' do
+        params = { projects: [project2.id, project3.id] }
+
+        merge_requests = described_class.new(user, params).execute
+
+        expect(merge_requests).to contain_exactly(merge_request3, merge_request4)
+      end
+
       it 'filters by commit sha' do
         merge_requests = described_class.new(
           user,
@@ -49,6 +57,16 @@ describe MergeRequestsFinder do
 
           expect(merge_requests).to contain_exactly(merge_request1, merge_request2, merge_request5)
         end
+
+        it 'filters by group projects including subgroups' do
+          # project3 is not in the group, so it should not return merge_request4
+          projects = [project3.id, project4.id]
+          params = { group_id: group.id, include_subgroups: true, projects: projects }
+
+          merge_requests = described_class.new(user, params).execute
+
+          expect(merge_requests).to contain_exactly(merge_request5)
+        end
       end
 
       it 'filters by non_archived' do