Test for the new exception of delegate_missing_to (#30191)

* Add test for the new exception of delegate_missing_to

* Add a changelog entry

* Only check for nil if NoMethodError was raised

* Make method private

* Have to pass both target name and value

* Inline the re-raise

[Rafael Mendonça França + Anton Khamets]

3 files changed, 22 insertions, 3 deletions

diff --git a/activesupport/CHANGELOG.md b/activesupport/CHANGELOG.md
index d5087f67af..ac1043df78 100644
--- a/activesupport/CHANGELOG.md
+++ b/activesupport/CHANGELOG.md
@@ -1,3 +1,8 @@
+*   `Module#delegate_missing_to` now raises `DelegationError` if target is nil,
+    similar to `Module#delegate`.
+
+    *Anton Khamets*
+
 *   Update `String#camelize` to provide feedback when wrong option is passed
 
     `String#camelize` was returning nil without any feedback when an
diff --git a/activesupport/lib/active_support/core_ext/module/delegation.rb b/activesupport/lib/active_support/core_ext/module/delegation.rb
index c979af9de3..1840dc942f 100644
--- a/activesupport/lib/active_support/core_ext/module/delegation.rb
+++ b/activesupport/lib/active_support/core_ext/module/delegation.rb
@@ -273,10 +273,16 @@ class Module
       def method_missing(method, *args, &block)
         if #{target}.respond_to?(method)
           #{target}.public_send(method, *args, &block)
-        elsif #{target}.nil?
-          raise DelegationError, "\#{method} delegated to #{target}, but #{target} is nil"
         else
-          super
+          begin
+            super
+          rescue NoMethodError
+            if #{target}.nil?
+              raise DelegationError, "\#{method} delegated to #{target}, but #{target} is nil"
+            else
+              raise
+            end
+          end
         end
       end
     RUBY
diff --git a/activesupport/test/core_ext/module_test.rb b/activesupport/test/core_ext/module_test.rb
index 69c8a312d8..e918823074 100644
--- a/activesupport/test/core_ext/module_test.rb
+++ b/activesupport/test/core_ext/module_test.rb
@@ -374,6 +374,14 @@ class ModuleTest < ActiveSupport::TestCase
     assert_match(/undefined method `my_fake_method' for/, e.message)
   end
 
+  def test_delegate_missing_to_raises_delegation_error_if_target_nil
+    e = assert_raises(Module::DelegationError) do
+      DecoratedTester.new(nil).name
+    end
+
+    assert_equal "name delegated to client, but client is nil", e.message
+  end
+
   def test_delegate_missing_to_affects_respond_to
     assert DecoratedTester.new(@david).respond_to?(:name)
     assert_not DecoratedTester.new(@david).respond_to?(:private_name)