Add Model#attributes helper; make test attributes explicit

Author: bf4

CHANGELOG.md

@@ -6,10 +6,14 @@ Breaking changes:
 
 Features:
 
+- [#2021](https://github.com/rails-api/active_model_serializers/pull/2021) ActiveModelSerializers::Model#attributes. (@bf4)
+
 Fixes:
 
 Misc:
 
+- [#2021](https://github.com/rails-api/active_model_serializers/pull/2021) Make test attributes explicit. Tests have Model#associations. (@bf4)
+
 ### [v0.10.4 (2017-01-06)](https://github.com/rails-api/active_model_serializers/compare/v0.10.3...v0.10.4)
 
 Misc:

README.md

@@ -116,7 +116,7 @@ class SomeResource < ActiveRecord::Base
 end
 # or
 class SomeResource < ActiveModelSerializers::Model
-  attr_accessor :title, :body
+  attributes :title, :body
 end
 ```
 
@@ -279,7 +279,7 @@ which is a simple serializable PORO (Plain-Old Ruby Object).
 
 ```ruby
 class MyModel < ActiveModelSerializers::Model
-  attr_accessor :id, :name, :level
+  attributes :id, :name, :level
 end
 ```
 

docs/howto/serialize_poro.md

@@ -2,13 +2,16 @@
 
 # How to serialize a Plain-Old Ruby Object (PORO)
 
-When you are first getting started with ActiveModelSerializers, it may seem only `ActiveRecord::Base` objects can be serializable, but pretty much any object can be serializable with ActiveModelSerializers.  Here is an example of a PORO that is serializable:
+When you are first getting started with ActiveModelSerializers, it may seem only `ActiveRecord::Base` objects can be serializable,
+but pretty much any object can be serializable with ActiveModelSerializers.
+Here is an example of a PORO that is serializable in most situations:
+
 ```ruby
 # my_model.rb
 class MyModel
   alias :read_attribute_for_serialization :send
   attr_accessor :id, :name, :level
-  
+
   def initialize(attributes)
     @id = attributes[:id]
     @name = attributes[:name]
@@ -21,12 +24,16 @@ class MyModel
 end
 ```
 
-Fortunately, ActiveModelSerializers provides a [`ActiveModelSerializers::Model`](https://github.com/rails-api/active_model_serializers/blob/master/lib/active_model_serializers/model.rb) which you can use in production code that will make your PORO a lot cleaner.  The above code now becomes:
+The spec that defines which methods ActiveModelSerializers expects is [ActiveModel/Serializer/Lint/Tests](../../lib/active_model/serializer/lint.rb).
+An implementation of the complete spec is included either for use or as reference:
+[`ActiveModelSerializers::Model`](../../lib/active_model_serializers/model.rb).
+You can use in production code that will make your PORO a lot cleaner.  The above code now becomes:
+
 ```ruby
 # my_model.rb
 class MyModel < ActiveModelSerializers::Model
-  attr_accessor :id, :name, :level
+  attributes :id, :name, :level
 end
 ```
 
-The default serializer would be `MyModelSerializer`.
+The default serializer would be `MyModelSerializer`.

lib/active_model_serializers.rb

@@ -38,6 +38,14 @@ def self.default_include_directive
     @default_include_directive ||= JSONAPI::IncludeDirective.new(config.default_includes, allow_wildcard: true)
   end
 
+  def self.silence_warnings
+    original_verbose = $VERBOSE
+    $VERBOSE = nil
+    yield
+  ensure
+    $VERBOSE = original_verbose
+  end
+
   require 'active_model/serializer/version'
   require 'active_model/serializer'
   require 'active_model/serializable_resource'

lib/active_model_serializers/model.rb

@@ -1,40 +1,71 @@
-# ActiveModelSerializers::Model is a convenient
-# serializable class to inherit from when making
-# serializable non-activerecord objects.
+# ActiveModelSerializers::Model is a convenient superclass when making serializable non-activerecord objects.
+# It also serves as documentation of an implementation that satisfies ActiveModel::Serializer::Lint::Tests.
 module ActiveModelSerializers
   class Model
-    include ActiveModel::Model
     include ActiveModel::Serializers::JSON
+    include ActiveModel::Model
 
-    attr_reader :attributes, :errors
+    # @method :attributes
+    #   - the attributes hash returned by `#attributes` will always be the value of the attributes passed in at initialization,
+    #   regardless of what attr_* methods were defined.  The attributes are modified
+    #   - unset attributes, rather than being nil, will not be included in the attributes hash, even when an `attr_accessor` exists.
+    #   - the only way to change the change the attributes after initialization is to mutate the `attributes` directly.  Accessor methods
+    #   will NOT mutate the attributes.  (This is a bug).
+    #
+    # For now, the Model only supports the notion of 'attributes'. In the tests, we do support 'associations' on the PORO,
+    # in order to adds accessors for values that should not appear in the attributes hash, as we model associations.
+    # However, it is not yet clear if it makes sense for a PORO to have associations outside of the tests.
+    def self.attributes(*names)
+      # Silence redefinition of methods warnings
+      ActiveModelSerializers.silence_warnings do
+        attr_accessor(*names)
+      end
+    end
+
+    # Support for validation and other ActiveModel::Errors
+    attr_reader :errors
+
+    attr_writer :updated_at
 
     def initialize(attributes = {})
-      @attributes = attributes && attributes.symbolize_keys
+      attributes ||= {} # protect against nil
+      @attributes = attributes.symbolize_keys.with_indifferent_access
       @errors = ActiveModel::Errors.new(self)
       super
     end
 
-    # Defaults to the downcased model name.
-    def id
-      attributes.fetch(:id) { self.class.name.downcase }
+    # The only way to change the attributes of an instance is to directly mutate the attributes.
+    #
+    #   model.attributes[:foo] = :bar
+    def attributes
+      instance_variable_get(:@attributes)
     end
 
-    # Defaults to the downcased model name and updated_at
-    def cache_key
-      attributes.fetch(:cache_key) { "#{self.class.name.downcase}/#{id}-#{updated_at.strftime('%Y%m%d%H%M%S%9N')}" }
+    # Defaults to the downcased model name.
+    # This probably isn't a good default, since it's not a unique instance identifier,
+    # but that's what is currently implemented \_('-')_/
+    # NOTE that though +id+ is defined, it will only show up
+    # in +attributes+ when it is passed in to the initializer or added to +attributes+,
+    # such as <tt>attributes[:id] = 5</tt>.
+    def id
+      instance_variable_get(:@attributes).fetch(:id) { self.class.model_name.name && self.class.model_name.name.downcase }
     end
 
-    # Defaults to the time the serializer file was modified.
+    # When not set, defaults to the time the file was modified.
+    # NOTE that though +updated_at+ and +updated_at=+ are defined, it will only show up
+    # in +attributes+ when it is passed in to the initializer or added to +attributes+,
+    # such as <tt>attributes[:updated_at] = Time.current</tt>.
     def updated_at
-      attributes.fetch(:updated_at) { File.mtime(__FILE__) }
+      defined?(@updated_at) ? @updated_at : File.mtime(__FILE__)
     end
 
-    def read_attribute_for_serialization(key)
-      if key == :id || key == 'id'
-        attributes.fetch(key) { id }
-      else
-        attributes[key]
-      end
+    # To customize model behavior, this method must be redefined. However,
+    # there are other ways of setting the +cache_key+ a serializer uses.
+    def cache_key
+      ActiveSupport::Cache.expand_cache_key([
+        self.class.model_name.name.downcase,
+        "#{id}-#{updated_at.strftime('%Y%m%d%H%M%S%9N')}"
+      ].compact)
     end
 
     # The following methods are needed to be minimally implemented for ActiveModel::Errors

test/action_controller/adapter_selector_test.rb

@@ -15,7 +15,7 @@ def render_using_adapter_override
         end
 
         def render_skipping_adapter
-          @profile = Profile.new(name: 'Name 1', description: 'Description 1', comments: 'Comments 1')
+          @profile = Profile.new(id: 'render_skipping_adapter_id', name: 'Name 1', description: 'Description 1', comments: 'Comments 1')
           render json: @profile, adapter: false
         end
       end
@@ -46,7 +46,7 @@ def test_render_using_adapter_override
 
       def test_render_skipping_adapter
         get :render_skipping_adapter
-        assert_equal '{"name":"Name 1","description":"Description 1","comments":"Comments 1"}', response.body
+        assert_equal '{"id":"render_skipping_adapter_id","name":"Name 1","description":"Description 1"}', response.body
       end
     end
   end

test/action_controller/json_api/fields_test.rb

@@ -5,7 +5,16 @@ module Serialization
     class JsonApi
       class FieldsTest < ActionController::TestCase
         class FieldsTestController < ActionController::Base
-          class PostSerializer < ActiveModel::Serializer
+          class AuthorWithName < Author
+            attributes :first_name, :last_name
+          end
+          class AuthorWithNameSerializer < AuthorSerializer
+            type 'authors'
+          end
+          class PostWithPublishAt < Post
+            attributes :publish_at
+          end
+          class PostWithPublishAtSerializer < ActiveModel::Serializer
             type 'posts'
             attributes :title, :body, :publish_at
             belongs_to :author
@@ -14,19 +23,19 @@ class PostSerializer < ActiveModel::Serializer
 
           def setup_post
             ActionController::Base.cache_store.clear
-            @author = Author.new(id: 1, first_name: 'Bob', last_name: 'Jones')
+            @author = AuthorWithName.new(id: 1, first_name: 'Bob', last_name: 'Jones')
             @comment1 = Comment.new(id: 7, body: 'cool', author: @author)
             @comment2 = Comment.new(id: 12, body: 'awesome', author: @author)
-            @post = Post.new(id: 1337, title: 'Title 1', body: 'Body 1',
-                             author: @author, comments: [@comment1, @comment2],
-                             publish_at: '2020-03-16T03:55:25.291Z')
+            @post = PostWithPublishAt.new(id: 1337, title: 'Title 1', body: 'Body 1',
+                                          author: @author, comments: [@comment1, @comment2],
+                                          publish_at: '2020-03-16T03:55:25.291Z')
             @comment1.post = @post
             @comment2.post = @post
           end
 
           def render_fields_works_on_relationships
             setup_post
-            render json: @post, serializer: PostSerializer, adapter: :json_api, fields: { posts: [:author] }
+            render json: @post, serializer: PostWithPublishAtSerializer, adapter: :json_api, fields: { posts: [:author] }
           end
         end
 

test/action_controller/json_api/transform_test.rb

@@ -5,9 +5,17 @@ module Serialization
     class JsonApi
       class KeyTransformTest < ActionController::TestCase
         class KeyTransformTestController < ActionController::Base
-          class Post < ::Model; end
-          class Author < ::Model; end
-          class TopComment < ::Model; end
+          class Post < ::Model
+            attributes :title, :body, :publish_at
+            associations :author, :top_comments
+          end
+          class Author < ::Model
+            attributes :first_name, :last_name
+          end
+          class TopComment < ::Model
+            attributes :body
+            associations :author, :post
+          end
           class PostSerializer < ActiveModel::Serializer
             type 'posts'
             attributes :title, :body, :publish_at

test/action_controller/namespace_lookup_test.rb

@@ -3,10 +3,16 @@
 module ActionController
   module Serialization
     class NamespaceLookupTest < ActionController::TestCase
-      class Book < ::Model; end
-      class Page < ::Model; end
-      class Chapter < ::Model; end
-      class Writer < ::Model; end
+      class Book < ::Model
+        attributes :title, :body
+        associations :writer, :chapters
+      end
+      class Chapter < ::Model
+        attributes :title
+      end
+      class Writer < ::Model
+        attributes :name
+      end
 
       module Api
         module V2
@@ -93,7 +99,7 @@ def explicit_namespace_as_symbol
             end
 
             def invalid_namespace
-              book = Book.new(title: 'New Post', body: 'Body')
+              book = Book.new(id: 'invalid_namespace_book_id', title: 'New Post', body: 'Body')
 
               render json: book, namespace: :api_v2
             end
@@ -205,7 +211,7 @@ def namespace_set_by_request_headers
 
         assert_serializer ActiveModel::Serializer::Null
 
-        expected = { 'title' => 'New Post', 'body' => 'Body' }
+        expected = { 'id' => 'invalid_namespace_book_id', 'title' => 'New Post', 'body' => 'Body' }
         actual = JSON.parse(@response.body)
 
         assert_equal expected, actual

test/action_controller/serialization_scope_name_test.rb

@@ -2,16 +2,16 @@
 
 module SerializationScopeTesting
   class User < ActiveModelSerializers::Model
-    attr_accessor :id, :name, :admin
+    attributes :id, :name, :admin
     def admin?
       admin
     end
   end
   class Comment < ActiveModelSerializers::Model
-    attr_accessor :id, :body
+    attributes :id, :body
   end
   class Post < ActiveModelSerializers::Model
-    attr_accessor :id, :title, :body, :comments
+    attributes :id, :title, :body, :comments
   end
   class PostSerializer < ActiveModel::Serializer
     attributes :id, :title, :body, :comments