Issue #21049 has been updated by matz (Yukihiro Matsumoto). I take all three "expected" in the first example. I'd rather wait for the request for the new (additional) APIs with real-world use-case. Matz. ---------------------------------------- Bug #21049: Reconsider handling of the numbered parameters and "it" parameter in `Binding#local_variables` https://bugs.ruby-lang.org/issues/21049#change-111864 * Author: mame (Yusuke Endoh) * Status: Open * Assignee: matz (Yukihiro Matsumoto) * Backport: 3.1: UNKNOWN, 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: UNKNOWN ---------------------------------------- Currently, `Binding#local_variable*` APIs wrongly handles the numbered parameters. ```ruby # Binding#local_variables includes numbered parameters that should not be visible "foo".tap do _1 "bar".tap do p binding.local_variables #=> expected: [], actual: [:_1] end end # Binding#local_variable_get can read numbered parameters that should not be readable "foo".tap do _1 "bar".tap do p binding.local_variable_get(:_1) #=> expected: NameError, actual: "foo" end end # Binding#local_variable_set can update numbered parameter "foo".tap do p _1 #=> "foo" binding.local_variable_set(:_1, "bar") # expected: NameError, actual: updates _1 p _1 #=> "bar" end ``` My proposal is to stop handling numbered parameters and "it" parameter in `Binding#local_variable*` APIs. ```ruby "foo".tap do _1 binding.local_variables #=> proposed: [] binding.local_variable_get(:_1) #=> proposed: NameError end ``` Here is a proof-of-concept patch. https://github.com/ruby/ruby/pull/12601 It would be theoretically possible to fix `Binding#local_variable*` APIs to handle numbered parameters while maintaining compatibility as much as possible. However, I think the implicit “it” parameter introduced in Ruby 3.4 poses a spec-level problem. This is because there is no way to distinguish between the implicit “it” parameter and a true local variable named "it". Also, I don't think numbered parameters are local variables, so I feel uncomfortable handling them by `Binding#local_variable*` APIs. If it is absolutely necessary to access numbered parameters or "it" parameter via binding, it would be good to introduce dedicated APIs for the purpose, as: * Binding#numbered_parameters #=> [:_1, :_2, :_3, ...] * Binding#numbered_parameter_get(:_1) #=> obj * Binding#numbered_parameter_defined?(:_1) #=> true or false * Binding#it_get #=> obj * Binding#it_defined? #=> true or false Personally, however, I do not see the need for these APIs currently. I implemented them as proof-of-concept in PR, but I am okay that they are not introduced. -- https://bugs.ruby-lang.org/