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[CLJS-471] Empty regexp causes Closure Compiler error Created: 13/Feb/13  Updated: 25/Apr/13

Status: Open
Project: ClojureScript
Component/s: None
Affects Version/s: None
Fix Version/s: None

Type: Defect Priority: Trivial
Reporter: Bodil Stokke Assignee: Michał Marczyk
Resolution: Unresolved Votes: 0
Labels: None

Attachments: Text File 0001-CLJS-471-prevent-empty-regexps-from-causing-compiler.patch    

 Description   

An empty regexp of the form #"" compiles to //, which is not an empty regexp but a comment, causing the code following the supposed regexp on the affected line to be commented out. This tends to cause compiler errors when Closure Compiler tries to parse it.

#"" should instead produce either /(?:)/ or new RegExp("").

 Comments   
Comment by Michał Marczyk [ 06/Apr/13 6:50 PM ]

Commit message:

CLJS-471: prevent empty regexps from causing compiler errors

This patch chooses to emit

  (new RegExp(""))

rather than

  /(?:)/

so that (pr-str #"") returns

  "#\"\""

rather than

  "#\"(?:)\""

A test for the above is included.
Comment by David Nolen [ 24/Apr/13 9:52 PM ]

I tried applying this in master, the included test fails.

Comment by Michał Marczyk [ 25/Apr/13 5:57 AM ]

Thanks for letting me know. I've checked the value of new RegExp("").source in a Node.js REPL (0.10.3) and it turns out to be '(?'. So, how important is it that we return "#\"\"" rather than "#\"(?\"" anyway? I'm thinking maybe not that much, seeing how regexp support in JS is different to that on the JVM in more fundamental ways. I'll just assume this is correct and attach a new patch accepting both representations soon. Of course if there's a better way to do it, I'll be happy to implement it.

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