[ruby-core:110483] [Ruby master Bug#19079] Modules included in a DelegateClass cannot override delegate methods

[ruby-core:110483] [Ruby master Bug#19079] Modules included in a DelegateClass cannot override delegate methods

[jonathanhefner (Jonathan Hefner)]

Issue #19079 has been reported by jonathanhefner (Jonathan Hefner).

----------------------------------------
Bug #19079: Modules included in a DelegateClass cannot override delegate methods
https://bugs.ruby-lang.org/issues/19079

* Author: jonathanhefner (Jonathan Hefner)
* Status: Open
* Priority: Normal
* ruby -v: ruby 3.1.2p20
* Backport: 2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: UNKNOWN
----------------------------------------
Because `DelegateClass` defines delegate methods on the class itself, those delegate methods come first in the method lookup chain.  This prevents included modules from overriding delegate methods:

  ```ruby
  Base = Class.new do
    def foo
      "base"
    end
  end

  Helper = Module.new do
    def foo
      "helper"
    end
  end

  WithHelper = DelegateClass(Base) { include Helper }

  WithHelper.new(Base.new).foo
  # => "base"
  ```

One possible solution would be to define the delegate methods in a separate module.  That way, other modules could come before it in the method lookup chain.



-- 
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[ruby-core:110484] [Ruby master Bug#19079] Modules included in a DelegateClass cannot override delegate methods

[jonathanhefner (Jonathan Hefner)]

Issue #19079 has been updated by jonathanhefner (Jonathan Hefner).


I have submitted a PR with the proposed solution: https://github.com/ruby/delegate/pull/14.

----------------------------------------
Bug #19079: Modules included in a DelegateClass cannot override delegate methods
https://bugs.ruby-lang.org/issues/19079#change-99804

* Author: jonathanhefner (Jonathan Hefner)
* Status: Open
* Priority: Normal
* ruby -v: ruby 3.1.2p20
* Backport: 2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: UNKNOWN
----------------------------------------
Because `DelegateClass` defines delegate methods on the class itself, those delegate methods come first in the method lookup chain.  This prevents included modules from overriding delegate methods:

  ```ruby
  Base = Class.new do
    def foo
      "base"
    end
  end

  Helper = Module.new do
    def foo
      "helper"
    end
  end

  WithHelper = DelegateClass(Base) { include Helper }

  WithHelper.new(Base.new).foo
  # => "base"
  ```

One possible solution would be to define the delegate methods in a separate module.  That way, other modules could come before it in the method lookup chain.



-- 
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[ruby-core:111104] [Ruby master Bug#19079] Modules included in a DelegateClass cannot override delegate methods

[matz (Yukihiro Matsumoto)]

Issue #19079 has been updated by matz (Yukihiro Matsumoto).

Status changed from Open to Rejected

The `DelegateClass` defines an anonymous class and defines forwarding methods to the class.  The reported (so-called) issue is a natural consequence of the above behavior. `include` add methods defined in a module **above** the current class, so forwarding methods have higher precedence. If you (re)define a method, it overwrites the forwarding method.

My opinion is that your assumption is wrong, so we don't need to fix. If you think we need to implement your assumption, you need to persuade us with the real world use-case.

Matz.


----------------------------------------
Bug #19079: Modules included in a DelegateClass cannot override delegate methods
https://bugs.ruby-lang.org/issues/19079#change-100371

* Author: jonathanhefner (Jonathan Hefner)
* Status: Rejected
* Priority: Normal
* ruby -v: ruby 3.1.2p20
* Backport: 2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: UNKNOWN
----------------------------------------
Because `DelegateClass` defines delegate methods on the class itself, those delegate methods come first in the method lookup chain.  This prevents included modules from overriding delegate methods:

  ```ruby
  Base = Class.new do
    def foo
      "base"
    end
  end

  Helper = Module.new do
    def foo
      "helper"
    end
  end

  WithHelper = DelegateClass(Base) { include Helper }

  WithHelper.new(Base.new).foo
  # => "base"
  ```

One possible solution would be to define the delegate methods in a separate module.  That way, other modules could come before it in the method lookup chain.



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[ruby-core:111126] [Ruby master Bug#19079] Modules included in a DelegateClass cannot override delegate methods

[matz (Yukihiro Matsumoto)]

Issue #19079 has been updated by matz (Yukihiro Matsumoto).


If you want to include a module to a delegated class, try the following:

```ruby
class WithHelper<DelegateClass(Base)
  include Helper
end
```

Matz.


----------------------------------------
Bug #19079: Modules included in a DelegateClass cannot override delegate methods
https://bugs.ruby-lang.org/issues/19079#change-100404

* Author: jonathanhefner (Jonathan Hefner)
* Status: Rejected
* Priority: Normal
* ruby -v: ruby 3.1.2p20
* Backport: 2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: UNKNOWN
----------------------------------------
Because `DelegateClass` defines delegate methods on the class itself, those delegate methods come first in the method lookup chain.  This prevents included modules from overriding delegate methods:

  ```ruby
  Base = Class.new do
    def foo
      "base"
    end
  end

  Helper = Module.new do
    def foo
      "helper"
    end
  end

  WithHelper = DelegateClass(Base) { include Helper }

  WithHelper.new(Base.new).foo
  # => "base"
  ```

One possible solution would be to define the delegate methods in a separate module.  That way, other modules could come before it in the method lookup chain.



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[ruby-core:111129] [Ruby master Bug#19079] Modules included in a DelegateClass cannot override delegate methods

[Hanmac (Hans Mackowiak)]

Issue #19079 has been updated by Hanmac (Hans Mackowiak).


you can also try prepend instead of include:

```ruby
WithHelper = DelegateClass(Base) { prepend Helper }
```

----------------------------------------
Bug #19079: Modules included in a DelegateClass cannot override delegate methods
https://bugs.ruby-lang.org/issues/19079#change-100407

* Author: jonathanhefner (Jonathan Hefner)
* Status: Rejected
* Priority: Normal
* ruby -v: ruby 3.1.2p20
* Backport: 2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: UNKNOWN
----------------------------------------
Because `DelegateClass` defines delegate methods on the class itself, those delegate methods come first in the method lookup chain.  This prevents included modules from overriding delegate methods:

  ```ruby
  Base = Class.new do
    def foo
      "base"
    end
  end

  Helper = Module.new do
    def foo
      "helper"
    end
  end

  WithHelper = DelegateClass(Base) { include Helper }

  WithHelper.new(Base.new).foo
  # => "base"
  ```

One possible solution would be to define the delegate methods in a separate module.  That way, other modules could come before it in the method lookup chain.



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 ______________________________________________
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[ruby-core:111132] [Ruby master Bug#19079] Modules included in a DelegateClass cannot override delegate methods

[jonathanhefner (Jonathan Hefner)]

Issue #19079 has been updated by jonathanhefner (Jonathan Hefner).


This issue occurred for a private module in Rails: https://github.com/rails/rails/pull/46189#discussion_r991440668.

Using `include` in a subclass works.  Using `prepend` also works, and is the workaround I used for the Rails module.

However, my proposed solution for this issue (https://github.com/ruby/delegate/pull/14) also solves #19079 with a performance improvement.

I opened this issue and #19079 because the current behavior seemed surprising to me.  In particular, I expected the `DelegateClass` block to behave just like a `Class.new` block.  I feel like that is a reasonable assumption based on [the documentation](https://github.com/ruby/delegate/blob/2e1272cadbf86a02a0084d03e336368556f0259e/lib/delegate.rb#L365-L369).

But, if my assumption is wrong, then I understand the decision.


----------------------------------------
Bug #19079: Modules included in a DelegateClass cannot override delegate methods
https://bugs.ruby-lang.org/issues/19079#change-100411

* Author: jonathanhefner (Jonathan Hefner)
* Status: Rejected
* Priority: Normal
* ruby -v: ruby 3.1.2p20
* Backport: 2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: UNKNOWN
----------------------------------------
Because `DelegateClass` defines delegate methods on the class itself, those delegate methods come first in the method lookup chain.  This prevents included modules from overriding delegate methods:

  ```ruby
  Base = Class.new do
    def foo
      "base"
    end
  end

  Helper = Module.new do
    def foo
      "helper"
    end
  end

  WithHelper = DelegateClass(Base) { include Helper }

  WithHelper.new(Base.new).foo
  # => "base"
  ```

One possible solution would be to define the delegate methods in a separate module.  That way, other modules could come before it in the method lookup chain.



-- 
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 ______________________________________________
 ruby-core mailing list -- ruby-core@ml.ruby-lang.org
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