Merge 0-10-stable into master (to fix breaking change). (#2023)

* Merge pull request #1990 from mxie/mx-result-typo

Fix typos and capitalization in Relationship Links docs [ci skip]

* Merge pull request #1992 from ojiry/bump_ruby_versions

Run tests by Ruby 2.2.6 and 2.3.3

* Merge pull request #1994 from bf4/promote_architecture

Promote important architecture description that answers a lot of questions we get
Conflicts:
	docs/ARCHITECTURE.md

* Merge pull request #1999 from bf4/typos

Fix typos [ci skip]

* Merge pull request #2000 from berfarah/patch-1

Link to 0.10.3 tag instead of `master` branch

* Merge pull request #2007 from bf4/check_ci

Test was failing due to change in JSON exception message when parsing empty string

* Swap out KeyTransform for CaseTransform (#1993)

* delete KeyTransform, use CaseTransform

* added changelog

Conflicts:
	CHANGELOG.md

* Merge pull request #2005 from kofronpi/support-ruby-2.4

Update jsonapi runtime dependency to 0.1.1.beta6

* Bump to v0.10.4

* Merge pull request #2018 from rails-api/bump_version

Bump to v0.10.4 [ci skip]
Conflicts:
	CHANGELOG.md

* Merge pull request #2019 from bf4/fix_method_redefined_warning

Fix AMS warnings

* Merge pull request #2020 from bf4/silence_grape_warnings

Silence Grape warnings

* Merge pull request #2017 from bf4/remove_warnings

Fix mt6 assert_nil warnings

* Updated isolated tests to assert correct behavior. (#2010)

* Updated isolated tests to assert correct behavior.
* Added check to get unsafe params if rails version is great than 5

* Merge pull request #2012 from bf4/cleanup_isolated_jsonapi_renderer_tests_a_bit

Cleanup assertions in isolated jsonapi renderer tests a bit

* Add Model#attributes helper; make test attributes explicit

* Fix model attributes accessors

* Fix typos

* Randomize testing of compatibility layer against regressions

* Test bugfix

* Add CHANGELOG

* Merge pull request #1981 from groyoh/link_doc

Fix relationship links doc
Conflicts:
	CHANGELOG.md

lib/active_model_serializers/model.rb

@@ -1,16 +1,40 @@
-# ActiveModelSerializers::Model is a convenient
-# serializable class to inherit from when making
-# serializable non-activerecord objects.
+# ActiveModelSerializers::Model is a convenient superclass for making your models
+# from Plain-Old Ruby Objects (PORO). It also serves as a reference implementation
+# that satisfies ActiveModel::Serializer::Lint::Tests.
 module ActiveModelSerializers
   class Model
     include ActiveModel::Serializers::JSON
     include ActiveModel::Model
 
-    class_attribute :attribute_names
+    # Declare names of attributes to be included in +sttributes+ hash.
+    # Is only available as a class-method since the ActiveModel::Serialization mixin in Rails
+    # uses an +attribute_names+ local variable, which may conflict if we were to add instance methods here.
+    #
+    # @overload attribute_names
+    #   @return [Array<Symbol>]
+    class_attribute :attribute_names, instance_writer: false, instance_reader: false
     # Initialize +attribute_names+ for all subclasses.  The array is usually
     # mutated in the +attributes+ method, but can be set directly, as well.
     self.attribute_names = []
 
+    # Easily declare instance attributes with setters and getters for each.
+    #
+    # All attributes to initialize an instance must have setters.
+    # However, the hash turned by +attributes+ instance method will ALWAYS
+    # be the value of the initial attributes, regardless of what accessors are defined.
+    # The only way to change the change the attributes after initialization is
+    # to mutate the +attributes+ directly.
+    # Accessor methods do NOT mutate the attributes.  (This is a bug).
+    #
+    # @note For now, the Model only supports the notion of 'attributes'.
+    #   In the tests, there is a special Model that also supports 'associations'. This is
+    #   important so that we can add accessors for values that should not appear in the
+    #   attributes hash when modeling associations. It is not yet clear if it
+    #   makes sense for a PORO to have associations outside of the tests.
+    #
+    # @overload attributes(names)
+    #   @param names [Array<String, Symbol>]
+    #   @param name [String, Symbol]
     def self.attributes(*names)
       self.attribute_names |= names.map(&:to_sym)
       # Silence redefinition of methods warnings
@@ -19,31 +43,90 @@ module ActiveModelSerializers
       end
     end
 
-    attr_reader :errors
-    # NOTE that +updated_at+ isn't included in +attribute_names+,
-    # which means it won't show up in +attributes+ unless a subclass has
-    # either <tt>attributes :updated_at</tt> which will redefine the methods
-    # or <tt>attribute_names << :updated_at</tt>.
-    attr_writer :updated_at
-    # NOTE that +id+ will always be in +attributes+.
-    attributes :id
+    # Opt-in to breaking change
+    def self.derive_attributes_from_names_and_fix_accessors
+      unless included_modules.include?(DeriveAttributesFromNamesAndFixAccessors)
+        prepend(DeriveAttributesFromNamesAndFixAccessors)
+      end
+    end
 
+    module DeriveAttributesFromNamesAndFixAccessors
+      def self.included(base)
+        # NOTE that +id+ will always be in +attributes+.
+        base.attributes :id
+      end
+
+      # Override the initialize method so that attributes aren't processed.
+      #
+      # @param attributes [Hash]
+      def initialize(attributes = {})
+        @errors = ActiveModel::Errors.new(self)
+        super
+      end
+
+      # Override the +attributes+ method so that the hash is derived from +attribute_names+.
+      #
+      # The the fields in +attribute_names+ determines the returned hash.
+      # +attributes+ are returned frozen to prevent any expectations that mutation affects
+      # the actual values in the model.
+      def attributes
+        self.class.attribute_names.each_with_object({}) do |attribute_name, result|
+          result[attribute_name] = public_send(attribute_name).freeze
+        end.with_indifferent_access.freeze
+      end
+    end
+
+    # Support for validation and other ActiveModel::Errors
+    # @return [ActiveModel::Errors]
+    attr_reader :errors
+
+    # (see #updated_at)
+    attr_writer :updated_at
+
+    # The only way to change the attributes of an instance is to directly mutate the attributes.
+    # @example
+    #
+    #   model.attributes[:foo] = :bar
+    # @return [Hash]
+    attr_reader :attributes
+
+    # @param attributes [Hash]
     def initialize(attributes = {})
+      attributes ||= {} # protect against nil
+      @attributes = attributes.symbolize_keys.with_indifferent_access
       @errors = ActiveModel::Errors.new(self)
       super
     end
 
-    # The the fields in +attribute_names+ determines the returned hash.
-    # +attributes+ are returned frozen to prevent any expectations that mutation affects
-    # the actual values in the model.
-    def attributes
-      attribute_names.each_with_object({}) do |attribute_name, result|
-        result[attribute_name] = public_send(attribute_name).freeze
-      end.with_indifferent_access.freeze
+    # 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 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>.
+    # @return [String, Numeric, Symbol]
+    def id
+      attributes.fetch(:id) do
+        defined?(@id) ? @id : self.class.model_name.name && self.class.model_name.name.downcase
+      end
+    end
+
+    # When not set, defaults to the time the file was modified.
+    #
+    # @note 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>.
+    # @return [String, Numeric, Time]
+    def updated_at
+      attributes.fetch(:updated_at) do
+        defined?(@updated_at) ? @updated_at : File.mtime(__FILE__)
+      end
     end
 
     # To customize model behavior, this method must be redefined. However,
     # there are other ways of setting the +cache_key+ a serializer uses.
+    # @return [String]
     def cache_key
       ActiveSupport::Cache.expand_cache_key([
         self.class.model_name.name.downcase,
@@ -51,12 +134,6 @@ module ActiveModelSerializers
       ].compact)
     end
 
-    # When no set, defaults to the time the file was modified.
-    # See NOTE by attr_writer :updated_at
-    def updated_at
-      defined?(@updated_at) ? @updated_at : File.mtime(__FILE__)
-    end
-
     # The following methods are needed to be minimally implemented for ActiveModel::Errors
     # :nocov:
     def self.human_attribute_name(attr, _options = {})