[ruby-core:56546] [ruby-trunk - Bug #8773] Binding#local_variables should work like #local_variable_set and #local_variable_get

Issue #8773 has been updated by jackdanger (Jack Danger).

File 0001-Allowing-binding-to-list-its-local-variables.patch added

With the addition of Binding#local_variable_get and Binding#local_variable_set the following seemed reasonable:

    def get_all_local_variables(bind)
      lvars = bind.send(:local_variables)
      # `lvars` should equal [:x, :y], but equals [:bind, :lvars]
      lvars.map {|name| bind.local_variable_get name }
    end
    x = 1
    y = 2
    get_all_local_variables(binding) # NameError: local variable `bind' not defined for #<Binding:0x0>

This is because `local_variables' is global and uses the current stack frame. That was not obvious to me. I could have just used binding.eval("local_variables") but that looked very strange when used alongside binding.local_variable_set and binding.local_variable_get.

Attached is a patch that gives Binding an instance method that properly lists the local variables defined in the binding. It now works like this:

    def get_all_local_variables(bind)
      lvars = bind.local_variables
      # `lvars` equals [:x, :y]
      lvars.map {|name| bind.local_variable_get name }
    end
    x = 1
    y = 2
    get_all_local_variables(binding) #=> [1, 2]

Here's a GitHub link if you want to see it with colors: https://github.com/JackDanger/ruby/pull/1/files
----------------------------------------
Bug #8773: Binding#local_variables should work like #local_variable_set and #local_variable_get
https://bugs.ruby-lang.org/issues/8773#change-41084

Author: jackdanger (Jack Danger)
Status: Open
Priority: Normal
Assignee: 
Category: core
Target version: current: 2.1.0
ruby -v: ruby 2.1.0dev (2013-08-11 trunk 42507) [x86_64-darwin12.4.0]
Backport: 1.9.3: UNKNOWN, 2.0.0: UNKNOWN


With the addition of Binding#local_variable_get and Binding#local_variable_set the following seemed reasonable:

    def get_all_local_variables(bind)
      lvars = bind.send(:local_variables)
      # `lvars` should equal [:x, :y], but equals [:bind, :lvars]
      lvars.map {|name| bind.local_variable_get name }
    end
    x = 1
    y = 2
    get_all_local_variables(binding) # NameError: local variable `bind' not defined for #<Binding:0x0>

This is because `local_variables' is global and uses the current stack frame. That was not obvious to me. I could have just used binding.eval("local_variables") but that looked very strange when used alongside binding.local_variable_set and binding.local_variable_get.

Attached is a patch that gives Binding an instance method that properly lists the local variables defined in the binding. It now works like this:

    def get_all_local_variables(bind)
      lvars = bind.local_variables
      # `lvars` equals [:x, :y]
      lvars.map {|name| bind.local_variable_get name }
    end
    x = 1
    y = 2
    set_everything_but_x_to_5(binding) # => [1, 1]

Here's a GitHub link if you want to see it with colors: https://github.com/JackDanger/ruby/pull/1/files


-- 
http://bugs.ruby-lang.org/