Move codeowner checks into Commits::CreateService

Iteratively, we've pushed these checks into a number of different
locations, however having a unified, single-location for these checks is
for more sustainable into the future. By moving the existing "web
request" checks into Commits::CreateService, we can remove the existing
checks previously added to the file editor, enable checks on the Commits
REST API (create/update/delete, cherry-pick, revert), and can remove the
:skip_web_ui_code_owner_validations ermergency workaround

ee/app/controllers/ee/projects/blob_controller.rb

@@ -12,6 +12,7 @@ module EE
       private
 
       def validate_codeowner_rules
+        return unless ::Feature.enabled?(:use_legacy_codeowner_validations)
         return if params[:file_path].blank?
 
         codeowners_error = codeowners_check_error(project, branch_name, params[:file_path])

ee/app/services/ee/commits/create_service.rb

@@ -11,6 +11,7 @@ module EE
       def validate!
         super
 
+        validate_against_codeowner_rules!
         validate_repository_size!
       end
 
@@ -21,6 +22,56 @@ module EE
           raise_error(size_checker.error_message.commit_error)
         end
       end
+
+      def validate_against_codeowner_rules!
+        return if ::Feature.enabled?(:use_legacy_codeowner_validations)
+
+        codeowners_error = check_against_codeowners(project, params[:branch_name], extracted_paths)
+
+        if codeowners_error.present?
+          raise_error(codeowners_error.tr("\n", " "))
+        end
+      end
+
+      def check_against_codeowners(project, branch, paths)
+        return if paths.empty?
+
+        ::Gitlab::CodeOwners::Validator.new(project, branch, paths).execute
+      end
+
+      def extracted_paths
+        paths = []
+
+        paths << params[:file_path].presence
+        paths << paths_from_actions
+        paths << paths_from_start_sha
+        paths << paths_from_commit(params[:commit])
+
+        paths.flatten.compact.uniq
+      end
+
+      def paths_from_actions
+        return unless params[:actions].present?
+
+        params[:actions].flat_map do |entry|
+          [entry[:file_path], entry[:previous_path]]
+        end
+      end
+
+      def paths_from_start_sha
+        return unless params[:start_sha].present?
+
+        commit = project.commit(params[:start_sha])
+        return unless commit
+
+        paths_from_commit(commit)
+      end
+
+      def paths_from_commit(commit)
+        return unless commit.present?
+
+        commit.raw_deltas.flat_map { |diff| [diff.new_path, diff.old_path] }
+      end
     end
   end
 end

ee/lib/ee/gitlab/checks/diff_check.rb

@@ -31,6 +31,8 @@ module EE
         # Issue to remove this feature flag:
         # https://gitlab.com/gitlab-org/gitlab/-/issues/217427
         def skip_web_ui_code_owner_validations?
+          return true unless ::Feature.enabled?(:use_legacy_codeowner_validations)
+
           ::Feature.enabled?(:skip_web_ui_code_owner_validations, project)
         end
 

ee/spec/controllers/ee/projects/blob_controller_spec.rb

@@ -8,9 +8,30 @@ RSpec.describe Projects::BlobController do
   let(:project) { create(:project, :public, :repository) }
 
   shared_examples "file matches a codeowners rule" do
+    # Expected behavior for both these contexts should be equivalent, however
+    #   the feature flag is used in code to control which code path is followed.
+    #
+    context ":use_legacy_codeowner_validations is true" do
+      before do
+        stub_feature_flags(use_legacy_codeowner_validations: true)
+      end
+
+      it_behaves_like "renders to the expected_view with an error msg"
+    end
+
+    context ":use_legacy_codeowner_validations is false" do
+      before do
+        stub_feature_flags(use_legacy_codeowner_validations: false)
+      end
+
+      it_behaves_like "renders to the expected_view with an error msg"
+    end
+  end
+
+  shared_examples "renders to the expected_view with an error msg" do
     let(:error_msg) { "Example error msg" }
 
-    it "renders to the edit page with an error msg" do
+    it "renders to the expected_view with an error msg" do
       default_params[:file_path] = "CHANGELOG"
 
       expect_next_instance_of(Gitlab::CodeOwners::Validator) do |validator|

ee/spec/lib/gitlab/checks/diff_check_spec.rb

@@ -125,24 +125,42 @@ RSpec.describe Gitlab::Checks::DiffCheck do
             expect(subject).to receive(:updated_from_web?).and_return(true)
           end
 
-          context "when skip_web_ui_code_owner_validations is disabled" do
+          context "when use_legacy_codeowner_validations is enabled" do
             before do
-              stub_feature_flags(skip_web_ui_code_owner_validations: false)
-              allow(project).to receive(:branch_requires_code_owner_approval?)
-                .once.and_return(true)
+              stub_feature_flags(use_legacy_codeowner_validations: true)
             end
 
-            it "returns an array of Proc(s)" do
-              validations = subject.send(:path_validations)
-
-              expect(validations.any?).to be_truthy
-              expect(validations.any? { |v| !v.is_a? Proc }).to be_falsy
+            context "when skip_web_ui_code_owner_validations is disabled" do
+              before do
+                stub_feature_flags(skip_web_ui_code_owner_validations: false)
+                allow(project).to receive(:branch_requires_code_owner_approval?)
+                  .once.and_return(true)
+              end
+
+              it "returns an array of Proc(s)" do
+                validations = subject.send(:path_validations)
+
+                expect(validations.any?).to be_truthy
+                expect(validations.any? { |v| !v.is_a? Proc }).to be_falsy
+              end
+
+              context "when skip_web_ui_code_owner_validations is enabled" do
+                before do
+                  stub_feature_flags(skip_web_ui_code_owner_validations: true)
+                  expect(project).not_to receive(:branch_requires_code_owner_approval?)
+                end
+
+                it "returns an empty array" do
+                  expect(subject.send(:path_validations)).to eq([])
+                end
+              end
             end
           end
 
-          context "when skip_web_ui_code_owner_validations is enabled" do
+          context "when use_legacy_codeowner_validations is disabled" do
             before do
-              stub_feature_flags(skip_web_ui_code_owner_validations: true)
+              stub_feature_flags(use_legacy_codeowner_validations: false)
+
               expect(project).not_to receive(:branch_requires_code_owner_approval?)
             end