Merge branch 'fix/471717-empty-changelog-config-yaml' into 'master'

Prevent 500 errors when evaluating empty changelog configs

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/166610



Merged-by: Joe Woodward <jwoodward@gitlab.com>
Approved-by: Naman Jagdish Gala <ngala@gitlab.com>
Approved-by: Eugie Limpin <elimpin@gitlab.com>
Co-authored-by: Joe Woodward <j@joewoodward.me>

lib/gitlab/changelog/config.rb

@@ -38,17 +38,13 @@ class Config
 
       def self.from_git(project, user = nil, path = nil)
         config_path = path.presence || DEFAULT_FILE_PATH
-        yaml = project.repository.changelog_config('HEAD', config_path)
+        config_yaml = project.repository.changelog_config('HEAD', config_path)
+        config_hash = YAML.safe_load(config_yaml) if config_yaml.present?
+        return new(project) if config_hash.nil?
 
-        if yaml.present?
-          begin
-            from_hash(project, YAML.safe_load(yaml), user)
-          rescue Psych::Exception
-            raise Error, "#{config_path} does not contain valid YAML"
-          end
-        else
-          new(project)
-        end
+        from_hash(project, config_hash, user)
+      rescue Psych::Exception
+        raise Error, "#{config_path} does not contain valid YAML"
       end
 
       def self.from_hash(project, hash, user = nil)

spec/lib/gitlab/changelog/config_spec.rb

@@ -2,7 +2,7 @@
 
 require 'spec_helper'
 
-RSpec.describe Gitlab::Changelog::Config do
+RSpec.describe Gitlab::Changelog::Config, feature_category: :source_code_management do
   include ProjectForksHelper
 
   let(:project) { build_stubbed(:project) }
@@ -57,17 +57,34 @@
       end
     end
 
-    context 'when changelog is empty' do
-      it 'returns the default configuration' do
-        allow(project.repository)
-          .to receive(:changelog_config)
-          .and_return("")
+    context 'when changelog config is empty' do
+      subject(:from_git) { described_class.from_git(project) }
+
+      shared_examples 'all attributes match the default config' do
+        let(:default_config) { described_class.new(project) }
+        let(:attributes) { %i[date_format categories template tag_regex always_credit_user_ids] }
+
+        it 'does not modify any attributes from the default config' do
+          attributes.each do |attribute|
+            expect(from_git.public_send(attribute)).to eql(default_config.public_send(attribute))
+          end
+        end
+      end
+
+      before do
+        allow(project.repository).to receive(:changelog_config).and_return(changelog_config_content)
+      end
+
+      context 'when changelog config does not contain a header' do
+        let(:changelog_config_content) { "" }
+
+        it_behaves_like 'all attributes match the default config'
+      end
 
-        expect(described_class)
-          .to receive(:new)
-          .with(project)
+      context 'when changelog config contains a header' do
+        let(:changelog_config_content) { "---\n\n" }
 
-        described_class.from_git(project)
+        it_behaves_like 'all attributes match the default config'
       end
     end
   end