Add support for ActiveModel::Errors.

Author: beauby

lib/jsonapi/rails/active_model_errors.rb

@@ -0,0 +1,39 @@
+module JSONAPI
+  module Rails
+    class ActiveModelError
+      def initialize(field, message, source)
+        @field   = field
+        @message = message
+        @source  = source
+
+        freeze
+      end
+
+      def as_jsonapi
+        {}.tap do |hash|
+          hash[:detail] = @message
+          hash[:title]  = "Invalid #{@field}" unless @field.nil?
+          hash[:source] = { pointer: @source } unless @source.nil?
+        end
+      end
+    end
+
+    class ActiveModelErrors
+      def initialize(errors, reverse_mapping)
+        @errors = errors
+        @reverse_mapping = reverse_mapping
+
+        freeze
+      end
+
+      def to_a
+        @errors.keys.flat_map do |key|
+          @errors.full_messages_for(key).map do |message|
+            ActiveModelError.new(key, message, @reverse_mapping[key])
+          end
+        end
+      end
+      alias to_array to_a
+    end
+  end
+end

lib/jsonapi/rails/railtie.rb

@@ -11,8 +11,8 @@ class Railtie < ::Rails::Railtie
       MEDIA_TYPE = 'application/vnd.api+json'.freeze
       PARSER = JSONAPI::Rails.parser
       RENDERERS = {
-        jsonapi:       JSONAPI::Rails.rails_renderer(SuccessRenderer),
-        jsonapi_error: JSONAPI::Rails.rails_renderer(ErrorRenderer)
+        jsonapi:        JSONAPI::Rails.rails_renderer(SuccessRenderer),
+        jsonapi_errors: JSONAPI::Rails.rails_renderer(ErrorsRenderer)
       }.freeze
 
       initializer 'jsonapi-rails.action_controller' do

lib/jsonapi/rails/renderer.rb

@@ -1,3 +1,4 @@
+require 'jsonapi/rails/active_model_errors'
 require 'jsonapi/serializable/renderer'
 
 module JSONAPI
@@ -16,9 +17,17 @@ def self.render(resources, options)
       end
     end
 
-    class ErrorRenderer
+    class ErrorsRenderer
       def self.render(errors, options)
-        # TODO(beauby): SerializableError inference on AR validation errors.
+        errors = [errors] unless errors.is_a?(Array)
+        errors = errors.flat_map do |error|
+          if error.is_a?(ActiveModel::Errors)
+            ActiveModelErrors.new(error, options[:_reverse_mapping]).to_a
+          else
+            error
+          end
+        end
+
         JSONAPI::Serializable::ErrorRenderer.render(errors, options)
       end
     end