1 files changed, 38 insertions, 6 deletions

diff --git a/activemodel/lib/active_model/errors.rb b/activemodel/lib/active_model/errors.rb
index 696e6d31da..2f883917b0 100644
--- a/activemodel/lib/active_model/errors.rb
+++ b/activemodel/lib/active_model/errors.rb
@@ -71,8 +71,8 @@ module ActiveModel
     #   end
     def initialize(base)
       @base     = base
-      @messages = Hash.new { |messages, attribute| messages[attribute] = [] }
-      @details  = Hash.new { |details, attribute| details[attribute] = [] }
+      @messages = apply_default_array({})
+      @details = apply_default_array({})
     end
 
     def initialize_dup(other) # :nodoc:
@@ -147,9 +147,9 @@ module ActiveModel
 
     # Delete messages for +key+. Returns the deleted messages.
     #
-    #   person.errors[:name]    # => ["cannot be nil"]
+    #   person.errors[:name]        # => ["cannot be nil"]
     #   person.errors.delete(:name) # => ["cannot be nil"]
-    #   person.errors[:name]    # => []
+    #   person.errors[:name]        # => []
     def delete(key)
       details.delete(key)
       messages.delete(key)
@@ -382,10 +382,21 @@ module ActiveModel
     end
 
     # Returns +true+ if an error on the attribute with the given message is
-    # present, +false+ otherwise. +message+ is treated the same as for +add+.
+    # present, or +false+ otherwise. +message+ is treated the same as for +add+.
     #
     #   person.errors.add :name, :blank
-    #   person.errors.added? :name, :blank # => true
+    #   person.errors.added? :name, :blank           # => true
+    #   person.errors.added? :name, "can't be blank" # => true
+    #
+    # If the error message requires an option, then it returns +true+ with
+    # the correct option, or +false+ with an incorrect or missing option.
+    #
+    #  person.errors.add :name, :too_long, { count: 25 }
+    #  person.errors.added? :name, :too_long, count: 25                     # => true
+    #  person.errors.added? :name, "is too long (maximum is 25 characters)" # => true
+    #  person.errors.added? :name, :too_long, count: 24                     # => false
+    #  person.errors.added? :name, :too_long                                # => false
+    #  person.errors.added? :name, "is too long"                            # => false
     def added?(attribute, message = :invalid, options = {})
       message = message.call if message.respond_to?(:call)
       message = normalize_message(attribute, message, options)
@@ -493,6 +504,16 @@ module ActiveModel
       I18n.translate(key, options)
     end
 
+    def marshal_dump
+      [@base, without_default_proc(@messages), without_default_proc(@details)]
+    end
+
+    def marshal_load(array)
+      @base, @messages, @details = array
+      apply_default_array(@messages)
+      apply_default_array(@details)
+    end
+
   private
     def normalize_message(attribute, message, options)
       case message
@@ -506,6 +527,17 @@ module ActiveModel
     def normalize_detail(message, options)
       { error: message }.merge(options.except(*CALLBACKS_OPTIONS + MESSAGE_OPTIONS))
     end
+
+    def without_default_proc(hash)
+      hash.dup.tap do |new_h|
+        new_h.default_proc = nil
+      end
+    end
+
+    def apply_default_array(hash)
+      hash.default_proc = proc { |h, key| h[key] = [] }
+      hash
+    end
   end
 
   # Raised when a validation cannot be corrected by end users and are considered