Fix bug with internal project snippets and project maintainer

app/policies/project_snippet_policy.rb

@@ -31,7 +31,7 @@ class ProjectSnippetPolicy < BasePolicy
          ~can?(:read_all_resources))
   end.prevent :read_snippet
 
-  rule { internal_snippet & ~is_author & ~admin }.policy do
+  rule { internal_snippet & ~is_author & ~admin & ~project.maintainer }.policy do
     prevent :update_snippet
     prevent :admin_snippet
   end
@@ -42,7 +42,7 @@ class ProjectSnippetPolicy < BasePolicy
     prevent :admin_snippet
   end
 
-  rule { is_author | admin }.policy do
+  rule { is_author | admin | project.maintainer }.policy do
     enable :read_snippet
     enable :update_snippet
     enable :admin_snippet

changelogs/unreleased/fj-207803-fix-project-snippet-policy-bug.yml

+---
+title: Fix bug deleting internal project snippets by project maintainer
+merge_request: 25792
+author:
+type: fixed

spec/policies/project_snippet_policy_spec.rb

@@ -20,6 +20,7 @@ describe ProjectSnippetPolicy do
   subject { described_class.new(current_user, snippet) }
 
   shared_examples 'regular user access rights' do
+    context 'not snippet author' do
       context 'project team member (non guest)' do
         before do
           project.add_developer(current_user)
@@ -36,12 +37,22 @@ describe ProjectSnippetPolicy do
           project.add_guest(current_user)
         end
 
-      context 'not snippet author' do
         it do
           expect_allowed(:read_snippet, :create_note)
           expect_disallowed(:admin_snippet)
         end
       end
+
+      context 'project team member (maintainer)' do
+        before do
+          project.add_maintainer(current_user)
+        end
+
+        it do
+          expect_allowed(:read_snippet, :create_note)
+          expect_allowed(*author_permissions)
+        end
+      end
     end
 
     context 'snippet author' do
@@ -69,6 +80,17 @@ describe ProjectSnippetPolicy do
         end
       end
 
+      context 'project team member (maintainer)' do
+        before do
+          project.add_maintainer(current_user)
+        end
+
+        it do
+          expect_allowed(:read_snippet, :create_note)
+          expect_allowed(*author_permissions)
+        end
+      end
+
       context 'not a project member' do
         it do
           expect_allowed(:read_snippet, :create_note)