Implement QuickActions::TargetService

app/controllers/projects/autocomplete_sources_controller.rb

 class Projects::AutocompleteSourcesController < Projects::ApplicationController
-  before_action :load_autocomplete_service
+  before_action :load_autocomplete_service, except: [:members]
 
   def members
     render json: ::Projects::ParticipantsService.new(@project, current_user).execute(target)
@@ -32,6 +32,8 @@ class Projects::AutocompleteSourcesController < Projects::ApplicationController
   end
 
   def target
-    @autocomplete_service.target(params[:type], params[:type_id])
+    QuickActions::TargetService
+      .new(project, current_user)
+      .execute(params[:type], params[:type_id])
   end
 end

app/services/preview_markdown_service.rb

@@ -29,9 +29,9 @@ class PreviewMarkdownService < BaseService
   end
 
   def find_commands_target
-    Projects::AutocompleteService
+    QuickActions::TargetService
       .new(project, current_user)
-      .target(commands_target_type, commands_target_id)
+      .execute(commands_target_type, commands_target_id)
   end
 
   def commands_target_type

app/services/projects/autocomplete_service.rb

@@ -51,16 +51,5 @@ module Projects
 
       QuickActions::InterpretService.new(project, current_user).available_commands(noteable)
     end
-
-    def target(type, type_id)
-      case type&.downcase
-      when 'issue'
-        IssuesFinder.new(current_user, project_id: project.id).find_by(iid: type_id) || project.issues.build
-      when 'mergerequest'
-        MergeRequestsFinder.new(current_user, project_id: project.id).find_by(iid: type_id) || project.merge_requests.build
-      when 'commit'
-        project.commit(type_id)
-      end
-    end
   end
 end

app/services/quick_actions/target_service.rb

+# frozen_string_literal: true
+
+module QuickActions
+  class TargetService < BaseService
+    def execute(type, type_id)
+      case type&.downcase
+      when 'issue'
+        issue(type_id)
+      when 'mergerequest'
+        merge_request(type_id)
+      when 'commit'
+        commit(type_id)
+      end
+    end
+
+    private
+
+    def issue(type_id)
+      IssuesFinder.new(current_user, project_id: project.id).find_by(iid: type_id) || project.issues.build
+    end
+
+    def merge_request(type_id)
+      MergeRequestsFinder.new(current_user, project_id: project.id).find_by(iid: type_id) || project.merge_requests.build
+    end
+
+    def commit(type_id)
+      return nil unless type_id
+
+      project.commit(type_id)
+    end
+  end
+end

spec/services/quick_actions/target_service_spec.rb

+require 'spec_helper'
+
+describe QuickActions::TargetService do
+  let(:project) { create(:project) }
+  let(:user) { create(:user) }
+  let(:service) { described_class.new(project, user) }
+
+  before do
+    project.add_maintainer(user)
+  end
+
+  describe '#execute' do
+    shared_examples 'no target' do |type_id:|
+      it 'returns nil' do
+        target = service.execute(type, type_id)
+
+        expect(target).to be_nil
+      end
+    end
+
+    shared_examples 'find target' do
+      it 'returns the target' do
+        found_target = service.execute(type, target_id)
+
+        expect(found_target).to eq(target)
+      end
+    end
+
+    shared_examples 'build target' do |type_id:|
+      it 'builds a new target' do
+        target = service.execute(type, type_id)
+
+        expect(target.project).to eq(project)
+        expect(target).to be_new_record
+      end
+    end
+
+    context 'for issue' do
+      let(:target) { create(:issue, project: project) }
+      let(:target_id) { target.iid }
+      let(:type) { 'Issue' }
+
+      it_behaves_like 'find target'
+      it_behaves_like 'build target', type_id: nil
+      it_behaves_like 'build target', type_id: -1
+    end
+
+    context 'for merge request' do
+      let(:target) { create(:merge_request, source_project: project) }
+      let(:target_id) { target.iid }
+      let(:type) { 'MergeRequest' }
+
+      it_behaves_like 'find target'
+      it_behaves_like 'build target', type_id: nil
+      it_behaves_like 'build target', type_id: -1
+    end
+
+    context 'for commit' do
+      let(:project) { create(:project, :repository) }
+      let(:target) { project.commit }
+      let(:target_id) { target.sha }
+      let(:type) { 'Commit' }
+
+      it_behaves_like 'find target'
+      it_behaves_like 'no target', type_id: 'invalid_sha'
+      it_behaves_like 'no target', type_id: nil
+    end
+
+    context 'for unknown type' do
+      let(:type) { 'unknown' }
+
+      it_behaves_like 'no target', type_id: :unused
+    end
+  end
+end