Issue #16157 has been updated by Dan0042 (Daniel DeLorme).
Ok, I misunderstood what `pass_keywords` was doing; I thought it would only apply to `baz(*args)` in this case.
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Misc #16157: What is the correct and *portable* way to do generic delegation?
https://bugs.ruby-lang.org/issues/16157#change-81539
* Author: Dan0042 (Daniel DeLorme)
* Status: Open
* Priority: Normal
* Assignee:
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With the keyword argument changes in 2.7 we must now specify keyword arguments explicitly when doing generic delegation. But this change is not compatible with 2.6, where it adds an empty hash to the argument list of methods that do not need/accept keyword arguments.
To illustrate the problem:
```ruby
class ProxyWithoutKW < BasicObject
def initialize(target)
@target = target
end
def method_missing(*a, &b)
@target.send(*a, &b)
end
end
class ProxyWithKW < BasicObject
def initialize(target)
@target = target
end
def method_missing(*a, **o, &b)
@target.send(*a, **o, &b)
end
end
class Test
def args(*a) a end
def arg(a) a end
def opts(**o) o end
end
# 2.6 2.7 3.0
ProxyWithoutKW.new(Test.new).args(42) # [42] [42] [42] ok
ProxyWithoutKW.new(Test.new).arg(42) # 42 42 42 ok
ProxyWithoutKW.new(Test.new).opts(k: 42) # {:k=>42} {:k=>42} +warn [{:k=>42}] incompatible with >= 2.7
ProxyWithKW.new(Test.new).args(42) # [42, {}] [42] [42] incompatible with <= 2.6
ProxyWithKW.new(Test.new).arg(42) # error 42 42 incompatible with <= 2.6
ProxyWithKW.new(Test.new).opts(k: 42) # {:k=>42} {:k=>42} +warn {:k=>42} must ignore warning? cannot use pass_positional_hash in 2.6
```
I don't know how to solve this, so I'm asking for the **official** correct way to write portable delegation code. And by **portable** I mean code that can be used in gems that target ruby 2.6 and above.
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