Add scope to CustomEmoji to find emoji for resource

Award Emoji can be awarded on many things and it can be difficult to
determine which namespace the awardable belongs to.

Thus to centralize the logic that finds the custom emoji for an
awardable, we introduce a scope on the CustomEmoji model that accepts a
resource (being either a Project or a Group), determines it's root
namespace, and finds all CustomEmoji for it. In combination with the
previous commit, all the Awardable models respond to #resource_parent,
which can be provided to this new scope.

This change fixes award emoji on merge requests, epics, and issues in
nested groups.

Changelog: fixed

app/models/award_emoji.rb

@@ -19,6 +19,8 @@ class AwardEmoji < ApplicationRecord
 
   participant :user
 
+  delegate :resource_parent, to: :awardable, allow_nil: true
+
   scope :downvotes, -> { named(DOWNVOTE_NAME) }
   scope :upvotes, -> { named(UPVOTE_NAME) }
   scope :named, -> (names) { where(name: names) }
@@ -63,7 +65,7 @@ class AwardEmoji < ApplicationRecord
   def url
     return if TanukiEmoji.find_by_alpha_code(name)
 
-    awardable.try(:namespace)&.custom_emoji&.by_name(name)&.first&.url
+    CustomEmoji.for_resource(resource_parent).by_name(name).select(:url).first&.url
   end
 
   def expire_cache

app/models/custom_emoji.rb

@@ -28,6 +28,19 @@ class CustomEmoji < ApplicationRecord
 
   alias_attribute :url, :file # this might need a change in https://gitlab.com/gitlab-org/gitlab/-/issues/230467
 
+  # Find custom emoji for the given resource.
+  # A resource can be either a Project or a Group, or anything responding to #root_ancestor.
+  # Usually it's the return value of #resource_parent on any model.
+  scope :for_resource, -> (resource) do
+    return none if resource.nil?
+
+    namespace = resource.root_ancestor
+
+    return none if namespace.nil?
+
+    namespace.custom_emoji
+  end
+
   private
 
   def valid_emoji_name

app/validators/gitlab/emoji_name_validator.rb

@@ -24,11 +24,9 @@ module Gitlab
     end
 
     def valid_custom_emoji?(record, value)
-      namespace = record.try(:awardable).try(:namespace)
+      resource = record.try(:resource_parent)
 
-      return unless namespace
-
-      namespace.custom_emoji&.by_name(value.to_s)&.any?
+      CustomEmoji.for_resource(resource).by_name(value.to_s).any?
     end
   end
 end

ee/spec/models/ee/award_emoji_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe AwardEmoji do
+  describe 'validations' do
+    context 'custom emoji' do
+      let_it_be(:user) { create(:user) }
+      let_it_be(:group) { create(:group) }
+      let_it_be(:emoji) { create(:custom_emoji, name: 'partyparrot', namespace: group) }
+
+      before do
+        group.add_maintainer(user)
+      end
+
+      it 'accepts custom emoji on epic' do
+        epic = create(:epic, group: group)
+        new_award = build(:award_emoji, user: user, awardable: epic, name: emoji.name)
+
+        expect(new_award).to be_valid
+      end
+
+      it 'accepts custom emoji on subgroup epic' do
+        subgroup = create(:group, parent: group)
+        epic = create(:epic, group: subgroup)
+        new_award = build(:award_emoji, user: user, awardable: epic, name: emoji.name)
+
+        expect(new_award).to be_valid
+      end
+    end
+  end
+end

spec/models/award_emoji_spec.rb

@@ -59,17 +59,41 @@ RSpec.describe AwardEmoji do
       end
     end
 
-    it 'accepts custom emoji' do
-      user  = create(:user)
-      group = create(:group)
-      group.add_maintainer(user)
+    context 'custom emoji' do
+      let_it_be(:user) { create(:user) }
+      let_it_be(:group) { create(:group) }
+      let_it_be(:emoji) { create(:custom_emoji, name: 'partyparrot', namespace: group) }
 
-      project = create(:project, namespace: group)
-      issue = create(:issue, project: project)
-      emoji = create(:custom_emoji, name: 'partyparrot', namespace: group)
-      new_award = build(:award_emoji, user: user, awardable: issue, name: emoji.name)
+      before do
+        group.add_maintainer(user)
+      end
+
+      %i[issue merge_request note_on_issue snippet].each do |awardable_type|
+        let_it_be(:project) { create(:project, namespace: group) }
+        let(:awardable) { create(awardable_type, project: project) }
+
+        it "is accepted on #{awardable_type}" do
+          new_award = build(:award_emoji, user: user, awardable: awardable, name: emoji.name)
+
+          expect(new_award).to be_valid
+        end
+      end
 
-      expect(new_award).to be_valid
+      it 'is accepted on subgroup issue' do
+        subgroup = create(:group, parent: group)
+        project = create(:project, namespace: subgroup)
+        issue = create(:issue, project: project)
+        new_award = build(:award_emoji, user: user, awardable: issue, name: emoji.name)
+
+        expect(new_award).to be_valid
+      end
+
+      it 'is not supported on personal snippet (yet)' do
+        snippet = create(:personal_snippet)
+        new_award = build(:award_emoji, user: snippet.author, awardable: snippet, name: 'null')
+
+        expect(new_award).not_to be_valid
+      end
     end
   end