Issue #20349 has been reported by baweaver (Brandon Weaver). ---------------------------------------- Feature #20349: Pattern Matching - Expose local variable captures https://bugs.ruby-lang.org/issues/20349 * Author: baweaver (Brandon Weaver) * Status: Open ---------------------------------------- In Regular Expressions we have the ability to utilize `Regexp.last_match` ([link](https://ruby-doc.org/3.2.2/Regexp.html#method-c-last_match)) to access the most recent match data from a regular expression match. I would like to propose that we have similar functionality for pattern matching: ```ruby require "rubocop" def ast_from(string) case string when String then processed_source_from(string).ast when RuboCop::ProcessedSource then string.ast when RuboCop::AST::Node then string else nil end end def longform_block?(node) node in [:block, # s(:block, [:send, target, target_method], # s(:send, s(:array), :select), [[:arg, v]], # s(:args, s(:arg, :v)), [:send, [:lvar, ^v], block_method] # s(:send, s(:lvar, :v), :even?)) ] end longform_block?(ast_from("[1, 2, 3].select { |v| v.even? }")) # => true # Name is not important, idea is, name can be debated. `source` is used to not # show AST nodes PatternMatch.last_match.transform_values(&:source) # => {:node=>"[1, 2, 3].select { |v| v.even? }", # :result=>"[1, 2, 3].select { |v| v.even? }", # :target=>"[1, 2, 3]", # :target_method=>:select, # :v=>:v, # :block_method=>:even?} # Hacky version to show how / where behavior could be captured def longform_block?(node) result = node in [:block, # s(:block, [:send, target, target_method], # s(:send, s(:array), :select), [[:arg, v]], # s(:args, s(:arg, :v)), [:send, [:lvar, ^v], block_method] # s(:send, s(:lvar, :v), :even?)) ] pp(binding.local_variables.to_h { [_1, binding.local_variable_get(_1).then { |s| s.source rescue s }] }) result end ``` -- https://bugs.ruby-lang.org/