1 files changed, 165 insertions, 0 deletions
diff --git a/activemodel/lib/active_model/error.rb b/activemodel/lib/active_model/error.rb
new file mode 100644
index 0000000000..6deab3578d
--- /dev/null
+++ b/activemodel/lib/active_model/error.rb
@@ -0,0 +1,165 @@
+# frozen_string_literal: true
+
+require "active_support/core_ext/class/attribute"
+
+module ActiveModel
+  # == Active \Model \Error
+  #
+  # Represents one single error
+  class Error
+    CALLBACKS_OPTIONS = [:if, :unless, :on, :allow_nil, :allow_blank, :strict]
+    MESSAGE_OPTIONS = [:message]
+
+    class_attribute :i18n_customize_full_message, default: false
+
+    def self.full_message(attribute, message, base_class) # :nodoc:
+      return message if attribute == :base
+      attribute = attribute.to_s
+
+      if i18n_customize_full_message && base_class.respond_to?(:i18n_scope)
+        attribute = attribute.remove(/\[\d\]/)
+        parts = attribute.split(".")
+        attribute_name = parts.pop
+        namespace = parts.join("/") unless parts.empty?
+        attributes_scope = "#{base_class.i18n_scope}.errors.models"
+
+        if namespace
+          defaults = base_class.lookup_ancestors.map do |klass|
+            [
+              :"#{attributes_scope}.#{klass.model_name.i18n_key}/#{namespace}.attributes.#{attribute_name}.format",
+              :"#{attributes_scope}.#{klass.model_name.i18n_key}/#{namespace}.format",
+            ]
+          end
+        else
+          defaults = base_class.lookup_ancestors.map do |klass|
+            [
+              :"#{attributes_scope}.#{klass.model_name.i18n_key}.attributes.#{attribute_name}.format",
+              :"#{attributes_scope}.#{klass.model_name.i18n_key}.format",
+            ]
+          end
+        end
+
+        defaults.flatten!
+      else
+        defaults = []
+      end
+
+      defaults << :"errors.format"
+      defaults << "%{attribute} %{message}"
+
+      attr_name = attribute.tr(".", "_").humanize
+      attr_name = base_class.human_attribute_name(attribute, default: attr_name)
+
+      I18n.t(defaults.shift,
+        default:  defaults,
+        attribute: attr_name,
+        message:   message)
+    end
+
+    def self.generate_message(attribute, type, base, options) # :nodoc:
+      type = options.delete(:message) if options[:message].is_a?(Symbol)
+      value = (attribute != :base ? base.send(:read_attribute_for_validation, attribute) : nil)
+
+      options = {
+        model: base.model_name.human,
+        attribute: base.class.human_attribute_name(attribute),
+        value: value,
+        object: base
+      }.merge!(options)
+
+      if base.class.respond_to?(:i18n_scope)
+        i18n_scope = base.class.i18n_scope.to_s
+        defaults = base.class.lookup_ancestors.flat_map do |klass|
+          [ :"#{i18n_scope}.errors.models.#{klass.model_name.i18n_key}.attributes.#{attribute}.#{type}",
+            :"#{i18n_scope}.errors.models.#{klass.model_name.i18n_key}.#{type}" ]
+        end
+        defaults << :"#{i18n_scope}.errors.messages.#{type}"
+
+        catch(:exception) do
+          translation = I18n.translate(defaults.first, options.merge(default: defaults.drop(1), throw: true))
+          return translation unless translation.nil?
+        end unless options[:message]
+      else
+        defaults = []
+      end
+
+      defaults << :"errors.attributes.#{attribute}.#{type}"
+      defaults << :"errors.messages.#{type}"
+
+      key = defaults.shift
+      defaults = options.delete(:message) if options[:message]
+      options[:default] = defaults
+
+      I18n.translate(key, options)
+    end
+
+    def initialize(base, attribute, type = :invalid, **options)
+      @base = base
+      @attribute = attribute
+      @raw_type = type
+      @type = type || :invalid
+      @options = options
+    end
+
+    def initialize_dup(other)
+      @attribute = @attribute.dup
+      @raw_type = @raw_type.dup
+      @type = @type.dup
+      @options = @options.deep_dup
+    end
+
+    attr_reader :base, :attribute, :type, :raw_type, :options
+
+    def message
+      case raw_type
+      when Symbol
+        self.class.generate_message(attribute, raw_type, @base, options.except(*CALLBACKS_OPTIONS))
+      else
+        raw_type
+      end
+    end
+
+    def detail
+      { error: raw_type }.merge(options.except(*CALLBACKS_OPTIONS + MESSAGE_OPTIONS))
+    end
+
+    def full_message
+      self.class.full_message(attribute, message, @base.class)
+    end
+
+    # See if error matches provided +attribute+, +type+ and +options+.
+    def match?(attribute, type = nil, **options)
+      if @attribute != attribute || (type && @type != type)
+        return false
+      end
+
+      options.each do |key, value|
+        if @options[key] != value
+          return false
+        end
+      end
+
+      true
+    end
+
+    def strict_match?(attribute, type, **options)
+      return false unless match?(attribute, type)
+
+      options == @options.except(*CALLBACKS_OPTIONS + MESSAGE_OPTIONS)
+    end
+
+    def ==(other)
+      other.is_a?(self.class) && attributes_for_hash == other.attributes_for_hash
+    end
+    alias eql? ==
+
+    def hash
+      attributes_for_hash.hash
+    end
+
+    protected
+      def attributes_for_hash
+        [@base, @attribute, @raw_type, @options.except(*CALLBACKS_OPTIONS)]
+      end
+  end
+end