Merge pull request #39140 from Shopify/missing-name-corner-case

Make NameError#missing_name work even for real Ruby NameError

actionpack/test/controller/helper_test.rb

@@ -88,7 +88,11 @@ class HelpersTypoControllerTest < ActiveSupport::TestCase
   def test_helper_typo_error_message
     e = assert_raise(NameError) { HelpersTypoController.helper "admin/users" }
     # This message is better if autoloading.
-    assert_equal "uninitialized constant Admin::UsersHelper", e.message
+    if RUBY_VERSION >= "2.6"
+      assert_equal "uninitialized constant Admin::UsersHelper\nDid you mean?  Admin::UsersHelpeR", e.message
+    else
+      assert_equal "uninitialized constant Admin::UsersHelper", e.message
+    end
   end
 end
 

activesupport/lib/active_support/core_ext/name_error.rb

@@ -14,9 +14,22 @@ class NameError
     # It extends NameError#message with spell corrections which are SLOW.
     # We should use original_message message instead.
     message = respond_to?(:original_message) ? original_message : self.message
+    return unless message.start_with?("uninitialized constant ")
 
-    unless /undefined local variable or method/.match?(message)
-      $1 if /((::)?([A-Z]\w*)(::[A-Z]\w*)*)$/ =~ message
+    receiver = begin
+      self.receiver
+    rescue ArgumentError
+      nil
+    end
+
+    if receiver == Object
+      name.to_s
+    elsif receiver
+      "#{real_mod_name(receiver)}::#{self.name}"
+    else
+      if match = message.match(/((::)?([A-Z]\w*)(::[A-Z]\w*)*)$/)
+        match[1]
+      end
     end
   end
 
@@ -35,4 +48,18 @@ class NameError
       missing_name == name.to_s
     end
   end
+
+  private
+    UNBOUND_METHOD_MODULE_NAME = Module.instance_method(:name)
+    private_constant :UNBOUND_METHOD_MODULE_NAME
+
+    if UnboundMethod.method_defined?(:bind_call)
+      def real_mod_name(mod)
+        UNBOUND_METHOD_MODULE_NAME.bind_call(mod)
+      end
+    else
+      def real_mod_name(mod)
+        UNBOUND_METHOD_MODULE_NAME.bind(mod).call
+      end
+    end
 end

activesupport/lib/active_support/dependencies.rb

@@ -592,8 +592,8 @@ module ActiveSupport #:nodoc:
         end
       end
 
-      name_error = NameError.new("uninitialized constant #{qualified_name}", const_name)
-      name_error.set_backtrace(caller.reject { |l| l.start_with?(__FILE__) })
+      name_error = uninitialized_constant(qualified_name, const_name, receiver: from_mod)
+      name_error.set_backtrace(caller.reject { |l| l.start_with? __FILE__ })
       raise name_error
     end
 
@@ -801,6 +801,16 @@ module ActiveSupport #:nodoc:
     end
 
     private
+      if RUBY_VERSION < "2.6"
+        def uninitialized_constant(qualified_name, const_name, receiver:)
+          NameError.new("uninitialized constant #{qualified_name}", const_name)
+        end
+      else
+        def uninitialized_constant(qualified_name, const_name, receiver:)
+          NameError.new("uninitialized constant #{qualified_name}", const_name, receiver: receiver)
+        end
+      end
+
       # Returns the original name of a class or module even if `name` has been
       # overridden.
       def real_mod_name(mod)

activesupport/test/core_ext/name_error_test.rb

@@ -11,6 +11,9 @@ class NameErrorTest < ActiveSupport::TestCase
     assert_equal "NameErrorTest::SomeNameThatNobodyWillUse____Really", exc.missing_name
     assert exc.missing_name?(:SomeNameThatNobodyWillUse____Really)
     assert exc.missing_name?("NameErrorTest::SomeNameThatNobodyWillUse____Really")
+    if RUBY_VERSION >= "2.6"
+      assert_equal NameErrorTest, exc.receiver
+    end
   end
 
   def test_missing_method_should_ignore_missing_name
@@ -19,5 +22,6 @@ class NameErrorTest < ActiveSupport::TestCase
     end
     assert_not exc.missing_name?(:Foo)
     assert_nil exc.missing_name
+    assert_equal self, exc.receiver
   end
 end