Merge pull request #26017 from kaspth/parameters-yaml-format-backward…

…scompatibility

Make Parameters support legacy YAML encodings.

actionpack/lib/action_controller/metal/strong_parameters.rb

@@ -7,6 +7,12 @@
 require 'rack/test'
 require 'stringio'
 require 'set'
+require 'yaml'
+
+# Wire up YAML format compatibility with Rails 4.2. Makes the YAML parser call
+# `init_with` when it encounters `!ruby/hash-with-ivars:ActionController::Parameters`,
+# instead of trying to parse it as a regular hash subclass.
+YAML.load_tags['!ruby/hash-with-ivars:ActionController::Parameters'] = 'ActionController::Parameters'
 
 module ActionController
   # Raised when a required parameter is missing.
@@ -604,6 +610,19 @@ def inspect
       "<#{self.class} #{@parameters} permitted: #{@permitted}>"
     end
 
+    def init_with(coder) # :nodoc:
+      if coder.map['elements']
+        # YAML's Hash subclass format from Rails 4.2, where keys and values
+        # were stored under an elements hash and `permitted` within an ivars hash.
+        @parameters = coder.map['elements'].with_indifferent_access
+        @permitted  = coder.map['ivars'][:@permitted]
+      else
+        # YAML's Object format. Only needed because of the format
+        # backwardscompability above, otherwise equivalent to YAML's initialization.
+        @parameters, @permitted = coder.map['parameters'], coder.map['permitted']
+      end
+    end
+
     def method_missing(method_sym, *args, &block)
       if @parameters.respond_to?(method_sym)
         message = <<-DEPRECATE.squish

actionpack/test/controller/parameters/serialization_test.rb

@@ -0,0 +1,32 @@
+require 'abstract_unit'
+require 'action_controller/metal/strong_parameters'
+require 'active_support/core_ext/string/strip'
+
+class ParametersSerializationTest < ActiveSupport::TestCase
+  test 'yaml serialization' do
+    assert_equal <<-end_of_yaml.strip_heredoc, YAML.dump(ActionController::Parameters.new(key: :value))
+      --- !ruby/object:ActionController::Parameters
+      parameters: !ruby/hash:ActiveSupport::HashWithIndifferentAccess
+        key: :value
+      permitted: false
+    end_of_yaml
+  end
+
+  test 'yaml deserialization' do
+    params = ActionController::Parameters.new(key: :value)
+    roundtripped = YAML.load(YAML.dump(params))
+
+    assert_equal params, roundtripped
+    assert_not roundtripped.permitted?
+  end
+
+  test 'yaml backwardscompatible with hash inheriting parameters' do
+    assert_equal ActionController::Parameters.new(key: :value), YAML.load(<<-end_of_yaml.strip_heredoc)
+      --- !ruby/hash-with-ivars:ActionController::Parameters
+      elements:
+        key: :value
+      ivars:
+        :@permitted: false
+    end_of_yaml
+  end
+end