Further clean-up of ActiveSupport::Callbacks

In #11195 I noticed a trailing comma in the docs, but I decided to
further clean it up.

What I have done:

* Clean up the trailing comma in the docs and some extra whitespace
  lines.
* Used `Array#extract` options to factor the repetitive pattern of
  `args.last.is_a(Hash) ? ...`
* Renamed the local var `config` to `options` in `define_callbacks`, as
  `options` seems to be the de facto name for the options objects.
* Renamed the local var `l` to `line` in `define_callback` (maybe it
  meant `lambda` in the context) as single `l` may look like `1` in some
  fonts.

1 files changed, 9 insertions, 10 deletions

diff --git a/activesupport/lib/active_support/callbacks.rb b/activesupport/lib/active_support/callbacks.rb
index 6168188d3b..5c738572a8 100644
--- a/activesupport/lib/active_support/callbacks.rb
+++ b/activesupport/lib/active_support/callbacks.rb
@@ -1,5 +1,6 @@
 require 'active_support/concern'
 require 'active_support/descendants_tracker'
+require 'active_support/core_ext/array/extract_options'
 require 'active_support/core_ext/class/attribute'
 require 'active_support/core_ext/kernel/reporting'
 require 'active_support/core_ext/kernel/singleton_class'
@@ -542,14 +543,12 @@ module ActiveSupport
         @callbacks = nil
         @chain.delete_if { |c| callback.duplicates?(c) }
       end
-
     end
 
     module ClassMethods
-
       def normalize_callback_params(filters, block) # :nodoc:
         type = CALLBACK_FILTER_TYPES.include?(filters.first) ? filters.shift : :before
-        options = filters.last.is_a?(Hash) ? filters.pop : {}
+        options = filters.extract_options!
         filters.unshift(block) if block
         [type, filters, options.dup]
       end
@@ -662,7 +661,7 @@ module ActiveSupport
       #   The current object and the return result of the callback will be called
       #   with the lambda.
       #
-      #     define_callbacks :validate, terminator: ->(target,result) { result == false },
+      #     define_callbacks :validate, terminator: ->(target, result) { result == false }
       #
       #   In this example, if any before validate callbacks returns +false+,
       #   other callbacks are not executed. Defaults to +false+, meaning no value
@@ -718,17 +717,17 @@ module ActiveSupport
       #
       #   would call <tt>Audit#save</tt>.
       def define_callbacks(*names)
-        config = names.last.is_a?(Hash) ? names.pop : {}
-        if config.key?(:terminator) && String === config[:terminator]
+        options = names.extract_options!
+        if options.key?(:terminator) && String === options[:terminator]
           ActiveSupport::Deprecation.warn "String based terminators are deprecated, please use a lambda"
-          value = config[:terminator]
-          l = class_eval "lambda { |result| #{value} }", __FILE__, __LINE__
-          config[:terminator] = lambda { |target, result| target.instance_exec(result, &l) }
+          value = options[:terminator]
+          line = class_eval "lambda { |result| #{value} }", __FILE__, __LINE__
+          options[:terminator] = lambda { |target, result| target.instance_exec(result, &line) }
         end
 
         names.each do |name|
           class_attribute "_#{name}_callbacks"
-          set_callbacks name, CallbackChain.new(name, config)
+          set_callbacks name, CallbackChain.new(name, options)
         end
       end