[ruby-core:37909] [Ruby 1.9 - Feature #4935] Quoted Label Form for 1.9 Hashes

Issue #4935 has been updated by Michael Edgar.


With the feature freeze coming up in a couple days, is there a chance this sees 1.9.3? It doesn't break any old syntax, only introduces new syntax, and rounds out the label feature of the 1.9 branch nicely.
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Feature #4935: Quoted Label Form for 1.9 Hashes
http://redmine.ruby-lang.org/issues/4935

Author: Michael Edgar
Status: Open
Priority: Normal
Assignee: 
Category: 
Target version: 


As discussed in the "Shorthand Hash Syntax for Strings" thread/feature request, several (including Matz) expressed interest in a parallel quoted form for the 1.9 label syntax:

  { foo: bar }
  { 'only-19': true }
  
  x = "hello"
  { "#{x}-world": Date.now }

This personally has come up for me with the new syntax: especially when dealing with command-line options, which often use hyphens, the quoted symbol form is necessary. Not being able to use the new syntax results in funny-looking hashes:

  { foo: bar, baz: qux, :'abc-def' => 1 }

I've attached a patch implementing this change. It allows a colon to follow single-quoted or double-quoted string literals to form a symbol key much like the label syntax introduced in 1.9. The examples listed at the start of this post all work fine. It introduces a new token - tLABEL_END - which replaces tSTRING_END when closing a symbol-label-literal. It introduces a single new grammar production for assoc, which is nearly purely syntactic sugar for the dsym grammar production; I've extracted dsym's implementation to a separate helper function, which is called from the dsym production and from the new label-style production.

I will immediately attach a new passing test for test_hash.rb in a followup post, once this has a feature # and ruby-core thread assigned to it.

NB: By removing the quote check on line 6580, one can make this feature work with any string literal (like "{ %q/foo-bar/: baz}", obviously doesn't work with heredocs) - I personally find this to be silly and inconsistent with the existing symbol syntax. Though it was fun to play with for a bit.


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