Infer type better with string extensions

ams.gemspec

@@ -31,8 +31,8 @@ Gem::Specification.new do |spec|
 
   spec.required_ruby_version = '>= 2.1'
 
-  rails_versions = ['>= 4.1', '< 6']
-  spec.add_runtime_dependency 'activemodel', rails_versions
+  # rails_versions = ['>= 4.1', '< 6']
+  # spec.add_runtime_dependency 'activemodel', rails_versions
   # 'activesupport', rails_versions
   # 'builder'
 

lib/ams/inflector.rb

@@ -0,0 +1,42 @@
+# frozen_string_literal: true
+
+# Adapted from
+# https://github.com/rails/rails/blob/master/activesupport/lib/active_support/inflector/methods.rb
+# https://github.com/mbj/inflecto/blob/master/lib/inflecto.rb
+module AMS
+  begin
+    require "active_support/inflector/methods"
+    # :nocov:
+    Inflector = ActiveSupport::Inflector
+    # :nocov:
+  rescue LoadError
+    module Inflector
+      extend self
+
+      # Makes an underscored, lowercase form from the expression in the string.
+      #
+      # Changes '::' to '/' to convert namespaces to paths.
+      #
+      #   underscore('ActiveModel')         # => "active_model"
+      #   underscore('ActiveModel::Errors') # => "active_model/errors"
+      #
+      # As a rule of thumb you can think of +underscore+ as the inverse of
+      # #camelize, though there are cases where that does not hold:
+      #
+      #   camelize(underscore('SSLError'))  # => "SslError"
+      def underscore(camel_cased_word)
+        return camel_cased_word unless /[A-Z-]|::/.match?(camel_cased_word)
+        word = camel_cased_word.to_s.gsub("::".freeze, "/".freeze)
+        word.gsub!(/([A-Z\d]+)([A-Z][a-z])/, '\1_\2'.freeze)
+        word.gsub!(/([a-z\d])([A-Z])/, '\1_\2'.freeze)
+        word.tr!("-".freeze, "_".freeze)
+        word.downcase!
+        word
+      end
+
+      def pluralize(word)
+        word + "s".freeze
+      end
+    end
+  end
+end

lib/ams/serializer.rb

@@ -1,6 +1,7 @@
 # frozen_string_literal: true
 
 require "json"
+require "ams/inflector"
 module AMS
   # Lightweight mapping of a model to a JSON API resource object
   # with attributes and relationships
@@ -62,11 +63,21 @@ module AMS
         $VERBOSE = original_verbose
       end
 
+      # @!visibility private
+      def _infer_type(base)
+        Inflector.pluralize(
+          Inflector.underscore(
+            base.name.split("::")[-1].sub(/Serializer/, "")
+          )
+         )
+      end
+
       def inherited(base)
         super
         base._attributes = _attributes.dup
         base._relations = _relations.dup
-        base._type = base.name.split("::")[-1].sub("Serializer", "").downcase
+        base._type = _infer_type(base)
+
         add_class_method "def class; #{base}; end", base
         add_instance_method "def id; object.id; end", base
       end