Fix inclusion to correctly disallow outside values

NEWS.md

@@ -70,6 +70,11 @@ is now:
   * *PR: [#1073]*
   * *Original issue: [#949]*
 
+* Fix `validate_inclusion_of` so that if it fails, it will no longer blow up
+  with the error "undefined method \`attribute_setter' for nil:NilClass".
+
+  * *Original issue: [#904]*
+
 ### Features
 
 * Add `required` and `optional` qualifiers to `belong_to` and `have_one`
@@ -143,6 +148,7 @@ is now:
 [#961]: https://github.com/thoughtbot/shoulda-matchers/issues/961
 [795ca68]: https://github.com/thoughtbot/shoulda-matchers/commit/795ca688bff08590dbd2ab6f2b51ea415e0c7473
 [#1089]: https://github.com/thoughtbot/shoulda-matchers/pulls/1089
+[#904]: https://github.com/thoughtbot/shoulda-matchers/issues/904
 
 ### Improvements
 

lib/shoulda/matchers/active_model/validate_inclusion_of_matcher.rb

@@ -465,8 +465,8 @@ def disallows_value_outside_of_array?
             end
           end
 
-          !values_outside_of_array.any? do |value|
-            allows_value_of(value, @low_message)
+          values_outside_of_array.all? do |value|
+            disallows_value_of(value, @low_message)
           end
         end
 

spec/unit/shoulda/matchers/active_model/validate_inclusion_of_matcher_spec.rb

@@ -448,9 +448,21 @@ def configure_validation_matcher(matcher)
 
     define_method(:valid_values) { args.fetch(:possible_values) }
 
-    it 'does not match a record with no validations' do
-      builder = build_object
-      expect_not_to_match_on_values(builder, possible_values)
+    context 'when the record has no validations' do
+      it 'passes when used in the negative' do
+        builder = build_object
+        expect_not_to_match_on_values(builder, possible_values)
+      end
+
+      it 'fails when used in the positive with an appropriate failure message' do
+        builder = build_object
+
+        assertion = lambda do
+          expect_to_match_on_values(builder, possible_values)
+        end
+
+        expect(&assertion).to fail
+      end
     end
 
     it 'matches given the same array of valid values' do

spec/unit_spec_helper.rb

@@ -1,6 +1,7 @@
 require_relative 'support/unit/load_environment'
 
 require 'rspec/rails'
+require 'rspec/matchers/fail_matchers'
 require 'shoulda-matchers'
 
 require 'spec_helper'
@@ -10,6 +11,8 @@
 end
 
 RSpec.configure do |config|
+  config.include RSpec::Matchers::FailMatchers
+
   UnitTests::ActionPackVersions.configure_example_group(config)
   UnitTests::ActiveModelHelpers.configure_example_group(config)
   UnitTests::ActiveModelVersions.configure_example_group(config)