From f8b637e47948bb67fcf7fc5091e6d3d8c3e1e009 Mon Sep 17 00:00:00 2001
From: Lee Richmond <lrichmond1@bloomberg.net>
Date: Mon, 5 Sep 2016 09:48:06 -0400
Subject: [PATCH] Ensure generator picks up ApplicationSerializer

ApplicationSerializer could exist, but not be loaded. So, we check
existence by looking at the filesystem instead of defined?.

Fixes https://github.com/rails-api/active_model_serializers/issues/1890
---
 CHANGELOG.md                                 |  1 +
 lib/generators/rails/serializer_generator.rb |  2 +-
 test/generators/serializer_generator_test.rb | 26 ++++++++++++++++----
 3 files changed, 23 insertions(+), 6 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 417197494..c00f90e29 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,7 @@ Breaking changes:
 Fixes:
 
 - [#1887](https://github.com/rails-api/active_model_serializers/pull/1887) Make the comment reflect what the function does (@johnnymo87)
+- [#1890](https://github.com/rails-api/active_model_serializers/issues/1890) Ensure generator Inherits from ApplicationSerializer when available (@richmolj)
 
 Features:
 
diff --git a/lib/generators/rails/serializer_generator.rb b/lib/generators/rails/serializer_generator.rb
index 16a47a61c..e670d5cf6 100644
--- a/lib/generators/rails/serializer_generator.rb
+++ b/lib/generators/rails/serializer_generator.rb
@@ -25,7 +25,7 @@ def association_names
       def parent_class_name
         if options[:parent]
           options[:parent]
-        elsif defined?(::ApplicationSerializer)
+        elsif 'ApplicationSerializer'.safe_constantize
           'ApplicationSerializer'
         else
           'ActiveModel::Serializer'
diff --git a/test/generators/serializer_generator_test.rb b/test/generators/serializer_generator_test.rb
index 562b93380..54a678b16 100644
--- a/test/generators/serializer_generator_test.rb
+++ b/test/generators/serializer_generator_test.rb
@@ -20,11 +20,10 @@ def test_generates_a_namespaced_serializer
   end
 
   def test_uses_application_serializer_if_one_exists
-    Object.const_set(:ApplicationSerializer, Class.new)
-    run_generator
-    assert_file 'app/serializers/account_serializer.rb', /class AccountSerializer < ApplicationSerializer/
-  ensure
-    Object.send :remove_const, :ApplicationSerializer
+    stub_safe_constantize(expected: 'ApplicationSerializer') do
+      run_generator
+      assert_file 'app/serializers/account_serializer.rb', /class AccountSerializer < ApplicationSerializer/
+    end
   end
 
   def test_uses_given_parent
@@ -54,4 +53,21 @@ def test_with_no_attributes_does_not_add_extra_space
       end
     end
   end
+
+  private
+
+  def stub_safe_constantize(expected:)
+    String.class_eval do
+      alias_method :old, :safe_constantize
+    end
+    String.send(:define_method, :safe_constantize) do
+      Class if self == expected
+    end
+
+    yield
+  ensure
+    String.class_eval do
+      alias_method :safe_constantize, :old
+    end
+  end
 end