Merge branch 'master' into laurocaetano-fix_send_file

* master: (536 commits)
  doc, API example on how to use `Model#exists?` with multiple IDs. [ci skip]
  Restore DATABASE_URL even if it's nil in connection_handler test
  [ci skip] - error_messages_for has been deprecated since 2.3.8 - lets reduce any confusion for users
  Ensure Active Record connection consistency
  Revert "ask the fixture set for the sql statements"
  Check `respond_to` before delegation due to: https://github.com/ruby/ruby/commit/d781caaf313b8649948c107bba277e5ad7307314
  Adding Hash#compact and Hash#compact! methods
  MySQL version 4.1 was EOL on December 31, 2009 We should at least recommend modern versions of MySQL to users.
  clear cache on body close so that cache remains during rendering
  add a more restricted codepath for templates fixes #13390
  refactor generator tests to use block form of Tempfile
  Fix typo [ci skip]
  Move finish_template as the last public method in the generator
  Minor typos fix [ci skip]
  make `change_column_null` reversible. Closes #13576.
  create/drop test and development databases only if RAILS_ENV is nil
  Revert "Speedup String#to"
  typo fix in test name. [ci skip].
  `core_ext/string/access.rb` test what we are documenting.
  Fix typo in image_tag documentation
  ...

Conflicts:
	actionpack/CHANGELOG.md

1 files changed, 12 insertions, 5 deletions

diff --git a/railties/lib/rails/application/configuration.rb b/railties/lib/rails/application/configuration.rb
index dd0b9c6d70..e902205a13 100644
--- a/railties/lib/rails/application/configuration.rb
+++ b/railties/lib/rails/application/configuration.rb
@@ -76,6 +76,7 @@ module Rails
         @paths ||= begin
           paths = super
           paths.add "config/database",    with: "config/database.yml"
+          paths.add "config/secrets",     with: "config/secrets.yml"
           paths.add "config/environment", with: "config/environment.rb"
           paths.add "lib/templates"
           paths.add "log",                with: "log/#{Rails.env}.log"
@@ -87,17 +88,23 @@ module Rails
         end
       end
 
-      # Loads and returns the configuration of the database.
+      # Loads and returns the entire raw configuration of database from
+      # values stored in `config/database.yml`.
       def database_configuration
-        yaml = paths["config/database"].first
-        if File.exist?(yaml)
+        yaml = Pathname.new(paths["config/database"].first || "")
+
+        config = if yaml.exist?
           require "erb"
-          YAML.load ERB.new(IO.read(yaml)).result
+          YAML.load(ERB.new(yaml.read).result) || {}
         elsif ENV['DATABASE_URL']
-          nil
+          # Value from ENV['DATABASE_URL'] is set to default database connection
+          # by Active Record.
+          {}
         else
           raise "Could not load database configuration. No such file - #{yaml}"
         end
+
+        config
       rescue Psych::SyntaxError => e
         raise "YAML syntax error occurred while parsing #{paths["config/database"].first}. " \
               "Please note that YAML must be consistently indented using spaces. Tabs are not allowed. " \