Bug #17179: Unexpected warning during value assignment to setter

• Status: Rejected
• Assignee: -
• Target version: -
• ruby -v: ruby 2.7.1p83 (2020-03-31 revision a0c7c23c9c) [x86_64-darwin19]
• Backport: 2.5: UNKNOWN, 2.6: UNKNOWN, 2.7: UNKNOWN

[bestwebua (Vladislav Trotsenko)]

some_instance = Class.new { def some_setter=(a:, b:); end }.new
setter_params = { a: 1, b: 2 }
some_instance.some_setter = setter_params # => {:a=>1, :b=>2}

# warning: Using the last argument as keyword parameters is deprecated; maybe ** should be added to the call
# warning: The called method `some_setter=' is defined here

some_instance.public_send(:some_setter=, **setter_params) # => nil
# No warninigs, everything is ok

If this behavior is okay, probably we need to add the ability to use the double splat operator with syntax sugar like in example below:

some_instance.some_setter = **setter_params

[bestwebua (Vladislav Trotsenko)]

• Description updated (diff)

[bestwebua (Vladislav Trotsenko)]

• Description updated (diff)

[jeremyevans0 (Jeremy Evans)]

• Status changed from Open to Rejected

This is expected behavior in Ruby 2.7, due to keyword argument separation. The warning is valid because the code will cause an ArgumentError in Ruby 3.

You should not use keywords parameters if you want to assign a hash. Instead, you should have the method accept a single hash argument. Note that calling the method directly with keywords will not cause a warning. some_instance.send(:some_setter=, :a=>1, :b=>2) doesn't warn, but some_instance.send(:some_setter=, {:a=>1, :b=>2}) does.

[sawa (Tsuyoshi Sawada)]

• Subject changed from Unexpected warning when value assignment to setter to Unexpected warning during value assignment to setter
• Description updated (diff)

[bestwebua (Vladislav Trotsenko)]

jeremyevans0 (Jeremy Evans) wrote in #note-3:

This is expected behavior in Ruby 2.7, due to keyword argument separation. The warning is valid because the code will cause an ArgumentError in Ruby 3.

You should not use keywords parameters if you want to assign a hash. Instead, you should have the method accept a single hash argument. Note that calling the method directly with keywords will not cause a warning. some_instance.send(:some_setter=, :a=>1, :b=>2) doesn't warn, but some_instance.send(:some_setter=, {:a=>1, :b=>2}) does.

Thank you, Jeremy!