[ruby-core:80414] [Ruby trunk Bug#13371] Syntax Error with regex when parens are omitted

Issue #13371 has been updated by shyouhei (Shyouhei Urabe).


ndn (Nikola Nenkov) wrote:
> Yes, but it was more of a question if it's a bug or not. Like should I use `%r//` when omitting parens as a principle? If yes - I would submit a PR in Rubocop and so on.

I can't say for sure from memory but this language ambiguity between regular expressions versus binary division is very hard to reroute, if not impossible.  So even if this is a bug, yes I recommend you to use %r.  I think it wouldn't be fixed anytime soon.

----------------------------------------
Bug #13371: Syntax Error with regex when parens are omitted
https://bugs.ruby-lang.org/issues/13371#change-63909

* Author: ndn (Nikola Nenkov)
* Status: Open
* Priority: Normal
* Assignee: 
* Target version: 
* ruby -v: 2.4.1
* Backport: 2.2: UNKNOWN, 2.3: UNKNOWN, 2.4: UNKNOWN
----------------------------------------
When you skip the parens of method invocations and pass a regex, you can get a `SyntaxError` if the regex starts with a space.

~~~ ruby
''.split(/ ./) # => []
''.split /./   # => []
''.split / ./  # !> SyntaxError: unexpected '.'
~~~

As per the syntax highlighting in my text editor and a discussion with another person, it seems that the opening slash is interpreted as division:

~~~ ruby
require 'ripper'

Ripper.lex("''.split /./")
  # =>
  # [[[1, 0], :on_tstring_beg, "'"],
  #  [[1, 1], :on_tstring_end, "'"],
  #  [[1, 2], :on_period, "."],
  #  [[1, 3], :on_ident, "split"],
  #  [[1, 8], :on_sp, " "],
  #  [[1, 9], :on_regexp_beg, "/"],
  #  #         ^^^
  #  [[1, 10], :on_tstring_content, "."],
  #  [[1, 11], :on_regexp_end, "/"]]

Ripper.lex("''.split / ./")
  # =>
  # [[[1, 0], :on_tstring_beg, "'"],
  #  [[1, 1], :on_tstring_end, "'"],
  #  [[1, 2], :on_period, "."],
  #  [[1, 3], :on_ident, "split"],
  #  [[1, 8], :on_sp, " "],
  #  [[1, 9], :on_op, "/"],
  #  #         ^^^
  #  [[1, 10], :on_sp, " "],
  #  [[1, 11], :on_period, "."],
  #  [[1, 12], :on_op, "/"]]
~~~


Reproducible with older versions as well (tried it until 2.1.2)



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