Inflections cleanup

1. Don’t use weird instance variable names
2. Don’t reach into the internals from the test (accessing ivars)
3. Properly reset the inflection rules after each test

(1) and (2) is to establish a clear boundary to make future refactors
easier.

(3) is to fix a bug where we modify the inflection rules and don’t reset
them properly after each test. We only attempt to do that for the `:en`
locale, but we have tests that modifies other locales that doesn’t get
cleaned up properly. For better or worse, the current API for loading
the default rules is to load `inflections.rb`, so let’s just do that and
reset the rules after each test.

Author: chancancode

actionpack/test/controller/params_wrapper_test.rb

@@ -339,27 +339,20 @@ def parse
 
   tests ParamswrappernewsController
 
-  def test_uses_model_attribute_names_with_irregular_inflection
-    with_dup do
-      ActiveSupport::Inflector.inflections do |inflect|
-        inflect.irregular "paramswrappernews_item", "paramswrappernews"
-      end
-
-      with_default_wrapper_options do
-        @request.env["CONTENT_TYPE"] = "application/json"
-        post :parse, params: { "username" => "sikachu", "test_attr" => "test_value" }
-        assert_parameters("username" => "sikachu", "test_attr" => "test_value", "paramswrappernews_item" => { "test_attr" => "test_value" })
-      end
-    end
+  def teardown
+    ActiveSupport::Inflector::Inflections.clear!
+    load "active_support/inflections.rb"
   end
 
-  private
+  def test_uses_model_attribute_names_with_irregular_inflection
+    ActiveSupport::Inflector.inflections do |inflect|
+      inflect.irregular "paramswrappernews_item", "paramswrappernews"
+    end
 
-    def with_dup
-      original = ActiveSupport::Inflector::Inflections.instance_variable_get(:@__instance__)[:en]
-      ActiveSupport::Inflector::Inflections.instance_variable_set(:@__instance__, en: original.dup)
-      yield
-    ensure
-      ActiveSupport::Inflector::Inflections.instance_variable_set(:@__instance__, en: original)
+    with_default_wrapper_options do
+      @request.env["CONTENT_TYPE"] = "application/json"
+      post :parse, params: { "username" => "sikachu", "test_attr" => "test_value" }
+      assert_parameters("username" => "sikachu", "test_attr" => "test_value", "paramswrappernews_item" => { "test_attr" => "test_value" })
     end
+  end
 end

activesupport/lib/active_support/inflector/inflections.rb

@@ -24,7 +24,7 @@ module Inflector
     # singularization rules that is runs. This guarantees that your rules run
     # before any of the rules that may already have been loaded.
     class Inflections
-      @__instance__ = {}
+      @instances = {}
 
       class Uncountables < Array
         def initialize
@@ -58,7 +58,11 @@ def to_regex(string)
       end
 
       def self.instance(locale = :en)
-        @__instance__[locale] ||= new
+        @instances[locale] ||= new
+      end
+
+      def self.clear! # :nodoc:
+        @instances = {}
       end
 
       attr_reader :plurals, :singulars, :uncountables, :humans, :acronyms, :acronym_regex
@@ -67,13 +71,6 @@ def initialize
         @plurals, @singulars, @uncountables, @humans, @acronyms, @acronym_regex = [], [], Uncountables.new, [], {}, /(?=a)b/
       end
 
-      # Private, for the test suite.
-      def initialize_dup(orig) # :nodoc:
-        %w(plurals singulars uncountables humans acronyms acronym_regex).each do |scope|
-          instance_variable_set("@#{scope}", orig.send(scope).dup)
-        end
-      end
-
       # Specifies a new acronym. An acronym must be specified as it will appear
       # in a camelized string. An underscore string that contains the acronym
       # will retain the acronym when passed to +camelize+, +humanize+, or

activesupport/test/inflector_test.rb

@@ -8,18 +8,10 @@ class InflectorTest < ActiveSupport::TestCase
   include InflectorTestCases
   include ConstantizeTestCases
 
-  def setup
-    # Dups the singleton before each test, restoring the original inflections later.
-    #
-    # This helper is implemented by setting @__instance__ because in some tests
-    # there are module functions that access ActiveSupport::Inflector.inflections,
-    # so we need to replace the singleton itself.
-    @original_inflections = ActiveSupport::Inflector::Inflections.instance_variable_get(:@__instance__)[:en]
-    ActiveSupport::Inflector::Inflections.instance_variable_set(:@__instance__, en: @original_inflections.dup)
-  end
-
   def teardown
-    ActiveSupport::Inflector::Inflections.instance_variable_set(:@__instance__, en: @original_inflections)
+    # Restore the default rules
+    ActiveSupport::Inflector::Inflections.clear!
+    load "active_support/inflections.rb"
   end
 
   def test_pluralize_plurals