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, 44 insertions, 16 deletions

diff --git a/actionmailer/lib/action_mailer/base.rb b/actionmailer/lib/action_mailer/base.rb
index 501fee55aa..275f657f8a 100644
--- a/actionmailer/lib/action_mailer/base.rb
+++ b/actionmailer/lib/action_mailer/base.rb
@@ -50,7 +50,7 @@ module ActionMailer
   #
   # * <tt>mail</tt> - Allows you to specify email to be sent.
   #
-  # The hash passed to the mail method allows you to specify any header that a Mail::Message
+  # The hash passed to the mail method allows you to specify any header that a <tt>Mail::Message</tt>
   # will accept (any valid Email header including optional fields).
   #
   # The mail method, if not passed a block, will inspect your views and send all the views with
@@ -229,7 +229,7 @@ module ActionMailer
   # An interceptor class must implement the <tt>:delivering_email(message)</tt> method which will be
   # called before the email is sent, allowing you to make modifications to the email before it hits
   # the delivery agents. Your class should make any needed modifications directly to the passed
-  # in Mail::Message instance.
+  # in <tt>Mail::Message</tt> instance.
   #
   # = Default Hash
   #
@@ -308,6 +308,28 @@ module ActionMailer
   # Note that unless you have a specific reason to do so, you should prefer using before_action
   # rather than after_action in your ActionMailer classes so that headers are parsed properly.
   #
+  # = Previewing emails
+  #
+  # You can preview your email templates visually by adding a mailer preview file to the
+  # <tt>ActionMailer::Base.preview_path</tt>. Since most emails do something interesting
+  # with database data, you'll need to write some scenarios to load messages with fake data:
+  #
+  #   class NotifierPreview < ActionMailer::Preview
+  #     def welcome
+  #       Notifier.welcome(User.first)
+  #     end
+  #   end
+  #
+  # Methods must return a <tt>Mail::Message</tt> object which can be generated by calling the mailer
+  # method without the additional <tt>deliver</tt>. The location of the mailer previews
+  # directory can be configured using the <tt>preview_path</tt> option which has a default
+  # of <tt>test/mailers/previews</tt>:
+  #
+  #     config.action_mailer.preview_path = "#{Rails.root}/lib/mailer_previews"
+  #
+  # An overview of all previews is accessible at <tt>http://localhost:3000/rails/mailers</tt>
+  # on a running development server instance.
+  #
   # = Configuration options
   #
   # These options are specified on the class level, like
@@ -317,7 +339,7 @@ module ActionMailer
   #   per the above section.
   #
   # * <tt>logger</tt> - the logger is used for generating information on the mailing run if available.
-  #   Can be set to nil for no logging. Compatible with both Ruby's own Logger and Log4r loggers.
+  #   Can be set to +nil+ for no logging. Compatible with both Ruby's own +Logger+ and Log4r loggers.
   #
   # * <tt>smtp_settings</tt> - Allows detailed configuration for <tt>:smtp</tt> delivery method:
   #   * <tt>:address</tt> - Allows you to use a remote mail server. Just change it from its default
@@ -335,8 +357,9 @@ module ActionMailer
   #     and starts to use it.
   #   * <tt>:openssl_verify_mode</tt> - When using TLS, you can set how OpenSSL checks the certificate. This is
   #     really useful if you need to validate a self-signed and/or a wildcard certificate. You can use the name
-  #     of an OpenSSL verify constant ('none', 'peer', 'client_once', 'fail_if_no_peer_cert') or directly the
-  #     constant  (OpenSSL::SSL::VERIFY_NONE, OpenSSL::SSL::VERIFY_PEER, ...).
+  #     of an OpenSSL verify constant (<tt>'none'</tt>, <tt>'peer'</tt>, <tt>'client_once'</tt>,
+  #     <tt>'fail_if_no_peer_cert'</tt>) or directly the constant (<tt>OpenSSL::SSL::VERIFY_NONE</tt>,
+  #     <tt>OpenSSL::SSL::VERIFY_PEER</tt>, ...).
   #
   # * <tt>sendmail_settings</tt> - Allows you to override options for the <tt>:sendmail</tt> delivery method.
   #   * <tt>:location</tt> - The location of the sendmail executable. Defaults to <tt>/usr/sbin/sendmail</tt>.
@@ -351,7 +374,7 @@ module ActionMailer
   #
   # * <tt>delivery_method</tt> - Defines a delivery method. Possible values are <tt>:smtp</tt> (default),
   #   <tt>:sendmail</tt>, <tt>:test</tt>, and <tt>:file</tt>. Or you may provide a custom delivery method
-  #   object e.g. MyOwnDeliveryMethodClass. See the Mail gem documentation on the interface you need to
+  #   object e.g. +MyOwnDeliveryMethodClass+. See the Mail gem documentation on the interface you need to
   #   implement for a custom delivery agent.
   #
   # * <tt>perform_deliveries</tt> - Determines whether emails are actually sent from Action Mailer when you
@@ -362,6 +385,7 @@ module ActionMailer
   #   <tt>delivery_method :test</tt>. Most useful for unit and functional testing.
   class Base < AbstractController::Base
     include DeliveryMethods
+    include Previews
 
     abstract!
 
@@ -373,6 +397,8 @@ module ActionMailer
     include AbstractController::AssetPaths
     include AbstractController::Callbacks
 
+    include ActionView::Layouts
+
     PROTECTED_IVARS = AbstractController::Rendering::DEFAULT_PROTECTED_INSTANCE_VARIABLES + [:@_action_has_layout]
 
     def _protected_ivars # :nodoc:
@@ -404,7 +430,7 @@ module ActionMailer
 
       # Register an Observer which will be notified when mail is delivered.
       # Either a class or a string can be passed in as the Observer. If a string is passed in
-      # it will be +constantize+d.
+      # it will be <tt>constantize</tt>d.
       def register_observer(observer)
         delivery_observer = (observer.is_a?(String) ? observer.constantize : observer)
         Mail.register_observer(delivery_observer)
@@ -462,11 +488,11 @@ module ActionMailer
         end
       end
 
-      # Wraps an email delivery inside of ActiveSupport::Notifications instrumentation.
+      # Wraps an email delivery inside of <tt>ActiveSupport::Notifications</tt> instrumentation.
       #
-      # This method is actually called by the Mail::Message object itself
-      # through a callback when you call +:deliver+ on the Mail::Message,
-      # calling +deliver_mail+ directly and passing a Mail::Message will do
+      # This method is actually called by the <tt>Mail::Message</tt> object itself
+      # through a callback when you call <tt>:deliver</tt> on the <tt>Mail::Message</tt>,
+      # calling +deliver_mail+ directly and passing a <tt>Mail::Message</tt> will do
       # nothing except tell the logger you sent the email.
       def deliver_mail(mail) #:nodoc:
         ActiveSupport::Notifications.instrument("deliver.action_mailer") do |payload|
@@ -542,18 +568,18 @@ module ActionMailer
       self.class.mailer_name
     end
 
-    # Allows you to pass random and unusual headers to the new Mail::Message
+    # Allows you to pass random and unusual headers to the new <tt>Mail::Message</tt>
     # object which will add them to itself.
     #
     #   headers['X-Special-Domain-Specific-Header'] = "SecretValue"
     #
     # You can also pass a hash into headers of header field names and values,
-    # which will then be set on the Mail::Message object:
+    # which will then be set on the <tt>Mail::Message</tt> object:
     #
     #   headers 'X-Special-Domain-Specific-Header' => "SecretValue",
     #           'In-Reply-To' => incoming.message_id
     #
-    # The resulting Mail::Message will have the following in its header:
+    # The resulting <tt>Mail::Message</tt> will have the following in its header:
     #
     #   X-Special-Domain-Specific-Header: SecretValue
     def headers(args = nil)
@@ -642,8 +668,8 @@ module ActionMailer
     # templates in the view paths using by default the mailer name and the
     # method name that it is being called from, it will then create parts for
     # each of these templates intelligently, making educated guesses on correct
-    # content type and sequence, and return a fully prepared Mail::Message
-    # ready to call +:deliver+ on to send.
+    # content type and sequence, and return a fully prepared <tt>Mail::Message</tt>
+    # ready to call <tt>:deliver</tt> on to send.
     #
     # For example:
     #
@@ -689,6 +715,8 @@ module ActionMailer
     #   end
     #
     def mail(headers = {}, &block)
+      return @_message if @_mail_was_called && headers.blank? && !block
+
       @_mail_was_called = true
       m = @_message