Simplify jsonapi_class configuration

Adds
• JSONAPI::Rails::SerializableClassMapping class
  Overriding Hash’s lookup can be confusing without creating an
  descendent class.
  - Old behavior
    inferrer.class == Hash
    Doesn’t make it obvious that there’s custom behavior
  - New behavior
    inferrer.class == JSONAPI::Rails::SerializableClassMapping
    Now it’s obvious where to look for the unusual behavior
  This setup also allows us to define the default mappings and the
  lookup behavior in separate configuration options
• configuration options for
  1. jsonapi_class_mapper
  2. jsonapi_class_mappings
  3. jsonapi_errors_class_mapper
    (fallback to jsonapi_class_mapper if nil)
  4. jsonapi_errors_class_mappings
Removes
• configration options for
  1. jsonapi_class
  2. jsonapi_errors_class

lib/generators/jsonapi/initializer/templates/initializer.rb

@@ -1,19 +1,22 @@
 JSONAPI::Rails.configure do |config|
-  # # Set a default serializable class mapping.
-  # config.jsonapi_class = Hash.new { |h, k|
-  #   names = k.to_s.split('::')
+  # # Set a default serializable class mapper
+  # config.jsonapi_class_mapper = -> (class_name) do
+  #   names = class_name.to_s.split('::')
   #   klass = names.pop
-  #   h[k] = [*names, "Serializable#{klass}"].join('::').safe_constantize
+  #   [*names, "Serializable#{klass}"].join('::').safe_constantize
+  # end
+  #
+  # # Set any default serializable class mappings
+  # config.jsonapi_class_mappings = {
   # }
   #
-  # # Set a default serializable class mapping for errors.
-  # config.jsonapi_errors_class = Hash.new { |h, k|
-  #   names = k.to_s.split('::')
-  #   klass = names.pop
-  #   h[k] = [*names, "Serializable#{klass}"].join('::').safe_constantize
-  # }.tap { |h|
-  #   h[:'ActiveModel::Errors'] = JSONAPI::Rails::SerializableActiveModelErrors
-  #   h[:Hash] = JSONAPI::Rails::SerializableErrorHash
+  # # Set a default serializable class mapper for errors.
+  # config.jsonapi_errors_class_mapper = config.jsonapi_class_mapper.dup
+  #
+  # # Set any default serializable class errors mappings
+  # config.jsonapi_errors_class_mappings = {
+  #   :'ActiveModel::Errors' => JSONAPI::Rails::SerializableActiveModelErrors,
+  #   :Hash => JSONAPI::Rails::SerializableErrorHash
   # }
   #
   # # Set a default JSON API object.

lib/jsonapi/rails/configuration.rb

@@ -7,22 +7,21 @@ class Configuration < ActiveSupport::InheritableOptions; end
 
     # @private
     module Configurable
-      DEFAULT_JSONAPI_CLASS = Hash.new do |h, k|
-        names = k.to_s.split('::')
+      DEFAULT_JSONAPI_CLASS_MAPPER = -> (class_name) do
+        names = class_name.to_s.split('::')
         klass = names.pop
-        h[k] = [*names, "Serializable#{klass}"].join('::').safe_constantize
-      end.freeze
+        [*names, "Serializable#{klass}"].join('::').safe_constantize
+      end
 
-      DEFAULT_JSONAPI_ERRORS_CLASS = DEFAULT_JSONAPI_CLASS.dup.merge!(
-        'ActiveModel::Errors'.to_sym =>
-        JSONAPI::Rails::SerializableActiveModelErrors,
-        'Hash'.to_sym => JSONAPI::Rails::SerializableErrorHash
-      ).freeze
+      DEFAULT_JSONAPI_CLASS_MAPPINGS = {}.freeze
 
-      DEFAULT_JSONAPI_OBJECT = {
-        version: '1.0'
+      DEFAULT_JSONAPI_ERROR_CLASS_MAPPINGS = {
+        :'ActiveModel::Errors' => JSONAPI::Rails::SerializableActiveModelErrors,
+        :Hash => JSONAPI::Rails::SerializableErrorHash
       }.freeze
 
+      DEFAULT_JSONAPI_OBJECT = { version: '1.0' }.freeze
+
       DEFAULT_JSONAPI_CACHE = ->() { nil }
 
       DEFAULT_JSONAPI_EXPOSE = lambda {
@@ -42,8 +41,10 @@ module Configurable
       DEFAULT_LOGGER = Logger.new(STDERR)
 
       DEFAULT_CONFIG = {
-        jsonapi_class: DEFAULT_JSONAPI_CLASS,
-        jsonapi_errors_class: DEFAULT_JSONAPI_ERRORS_CLASS,
+        jsonapi_class_mapper: DEFAULT_JSONAPI_CLASS_MAPPER,
+        jsonapi_class_mappings: DEFAULT_JSONAPI_CLASS_MAPPINGS,
+        jsonapi_errors_class_mapper: nil,
+        jsonapi_errors_class_mappings: DEFAULT_JSONAPI_ERROR_CLASS_MAPPINGS,
         jsonapi_cache:   DEFAULT_JSONAPI_CACHE,
         jsonapi_expose:  DEFAULT_JSONAPI_EXPOSE,
         jsonapi_fields:  DEFAULT_JSONAPI_FIELDS,

lib/jsonapi/rails/controller/hooks.rb

@@ -1,4 +1,5 @@
 require 'jsonapi/rails/configuration'
+require 'jsonapi/rails/serializable_class_mapping'
 
 module JSONAPI
   module Rails
@@ -11,14 +12,22 @@ module Hooks
         # Overridden by the `class` renderer option.
         # @return [Hash{Symbol=>Class}]
         def jsonapi_class
-          JSONAPI::Rails.config[:jsonapi_class].dup
+          JSONAPI::Rails::SerializableClassMapping.new(
+            JSONAPI::Rails.config[:jsonapi_class_mappings].dup,
+            &JSONAPI::Rails.config[:jsonapi_class_mapper]
+          )
         end
 
         # Hook for serializable class mapping (for errors).
         # Overridden by the `class` renderer option.
         # @return [Hash{Symbol=>Class}]
         def jsonapi_errors_class
-          JSONAPI::Rails.config[:jsonapi_errors_class].dup
+          class_mapper =
+            JSONAPI::Rails.config[:jsonapi_errors_class_mapper]&.dup ||
+            JSONAPI::Rails.config[:jsonapi_class_mapper].dup
+          JSONAPI::Rails::SerializableClassMapping.new(
+            JSONAPI::Rails.config[:jsonapi_errors_class_mappings], &class_mapper
+          )
         end
 
         # Hook for the jsonapi object.

lib/jsonapi/rails/serializable_class_mapping.rb

@@ -0,0 +1,11 @@
+module JSONAPI
+  module Rails
+    class SerializableClassMapping < Hash
+      def initialize(default_mappings = {}, &block)
+        super() do |hash, class_name_sym|
+          hash[class_name_sym] = yield(class_name_sym.to_s).safe_constantize
+        end
+      end
+    end
+  end
+end