Redis: always return config hash

This is to prevent issues like
https://gitlab.com/gitlab-org/omnibus-gitlab/-/issues/6177.

lib/gitlab/redis/cache.rb

@@ -8,7 +8,9 @@ module Gitlab
       private
 
       def raw_config_hash
-        super || { url: 'redis://localhost:6380' }
+        config = super
+        config[:url] = 'redis://localhost:6380' if config[:url].blank?
+        config
       end
     end
   end

lib/gitlab/redis/queues.rb

@@ -2,6 +2,7 @@
 
 # We need this require for MailRoom
 require_relative 'wrapper' unless defined?(::Gitlab::Redis::Wrapper)
+require 'active_support/core_ext/object/blank'
 
 module Gitlab
   module Redis
@@ -12,7 +13,9 @@ module Gitlab
       private
 
       def raw_config_hash
-        super || { url: 'redis://localhost:6381' }
+        config = super
+        config[:url] = 'redis://localhost:6381' if config[:url].blank?
+        config
       end
     end
   end

lib/gitlab/redis/shared_state.rb

@@ -11,7 +11,9 @@ module Gitlab
       private
 
       def raw_config_hash
-        super || { url: 'redis://localhost:6382' }
+        config = super
+        config[:url] = 'redis://localhost:6382' if config[:url].blank?
+        config
       end
     end
   end

lib/gitlab/redis/wrapper.rb

@@ -133,6 +133,8 @@ module Gitlab
 
         if config_data
           config_data.is_a?(String) ? { url: config_data } : config_data.deep_symbolize_keys
+        else
+          { url: '' }
         end
       end
 

spec/support/redis/redis_shared_examples.rb

@@ -16,6 +16,7 @@ RSpec.shared_examples "redis_shared_examples" do
   let(:sentinel_port) { 26379 }
   let(:config_with_environment_variable_inside) { "spec/fixtures/config/redis_config_with_env.yml"}
   let(:config_env_variable_url) {"TEST_GITLAB_REDIS_URL"}
+  let(:rails_root) { Dir.mktmpdir('redis_shared_examples') }
 
   before do
     allow(described_class).to receive(:config_file_name).and_return(Rails.root.join(config_file_name).to_s)
@@ -29,8 +30,6 @@ RSpec.shared_examples "redis_shared_examples" do
   describe '.config_file_name' do
     subject { described_class.config_file_name }
 
-    let(:rails_root) { Dir.mktmpdir('redis_shared_examples') }
-
     before do
       # Undo top-level stub of config_file_name because we are testing that method now.
       allow(described_class).to receive(:config_file_name).and_call_original
@@ -237,6 +236,23 @@ RSpec.shared_examples "redis_shared_examples" do
         described_class.with { |_redis_shared_example| true }
       end
     end
+
+    context 'when there is no config at all' do
+      before do
+        # Undo top-level stub of config_file_name because we are testing that method now.
+        allow(described_class).to receive(:config_file_name).and_call_original
+
+        allow(described_class).to receive(:rails_root).and_return(rails_root)
+      end
+
+      after do
+        FileUtils.rm_rf(rails_root)
+      end
+
+      it 'can run an empty block' do
+        expect { described_class.with { nil } }.not_to raise_error
+      end
+    end
   end
 
   describe '#sentinels' do