Added a shared section to config/database.yml that will be loaded for all environments

Author: pschambacher

railties/CHANGELOG.md

@@ -1,8 +1,12 @@
+*   Added a shared section to config/database.yml that will be loaded for all environments.
+
+    *Pierre Schambacher*
+
 *   Namespace error pages' CSS selectors to stop the styles from bleeding into other pages
-    when using Turbolinks. 
-    
+    when using Turbolinks.
+
     *Jan Krutisch*
 
-    
+
 
 Please check [5-1-stable](https://github.com/rails/rails/blob/5-1-stable/railties/CHANGELOG.md) for previous changes.

railties/lib/rails/application/configuration.rb

@@ -133,7 +133,14 @@ def database_configuration
         config = if yaml && yaml.exist?
           require "yaml"
           require "erb"
-          YAML.load(ERB.new(yaml.read).result) || {}
+          loaded_yaml = YAML.load(ERB.new(yaml.read).result) || {}
+          shared = loaded_yaml.delete("shared")
+          if shared
+            loaded_yaml.each do |_k, values|
+              values.reverse_merge!(shared)
+            end
+          end
+          Hash.new(shared).merge(loaded_yaml)
         elsif ENV["DATABASE_URL"]
           # Value from ENV['DATABASE_URL'] is set to default database connection
           # by Active Record.

railties/test/application/configuration_test.rb

@@ -1407,6 +1407,40 @@ def index
       assert_match "config/database", err.message
     end
 
+    test "loads database.yml using shared keys" do
+      app_file "config/database.yml", <<-YAML
+        shared:
+          username: bobby
+          adapter: sqlite3
+
+        development:
+          database: 'dev_db'
+      YAML
+
+      app "development"
+
+      ar_config = Rails.application.config.database_configuration
+      assert_equal "sqlite3", ar_config["development"]["adapter"]
+      assert_equal "bobby",   ar_config["development"]["username"]
+      assert_equal "dev_db",  ar_config["development"]["database"]
+    end
+
+    test "loads database.yml using shared keys for undefined environments" do
+      app_file "config/database.yml", <<-YAML
+        shared:
+          username: bobby
+          adapter: sqlite3
+          database: 'dev_db'
+      YAML
+
+      app "development"
+
+      ar_config = Rails.application.config.database_configuration
+      assert_equal "sqlite3", ar_config["development"]["adapter"]
+      assert_equal "bobby",   ar_config["development"]["username"]
+      assert_equal "dev_db",  ar_config["development"]["database"]
+    end
+
     test "config.action_mailer.show_previews defaults to true in development" do
       app "development"