Bug 20142

Summary: REGRESSION(r35245): /=/ weirdness
Product: WebKit Reporter: Will Moffat <wdm>
Component: JavaScriptCoreAssignee: Nobody <webkit-unassigned>
Status: RESOLVED FIXED    
Severity: Normal CC: ap, oliver
Priority: P1 Keywords: Regression
Version: 528+ (Nightly build)   
Hardware: All   
OS: All   

Description Will Moffat 2008-07-23 07:41:15 PDT
The regexp /=/ behaves very strangely unless you escape the equals sign. Firefox does not require the escape.


WebKit: 
/=/.toString()  --> "//"   BUG?
/=/.test('=')   --> true   ok
'='.match(/=/)  --> [""]   BUG?
'='.match(/\=/) --> ["="]  ok 

FF3:
/=/.toString()  --> "/=/"  OK
/=/.test('=')   --> true   OK
'='.match(/=/)  --> ["="]  OK   
'='.match(/\=/) --> ["="]  OK
Comment 1 Alexey Proskuryakov 2008-07-23 08:03:28 PDT
Weird. Confirmed as a regression with r35291.
Comment 2 Alexey Proskuryakov 2008-07-23 08:38:16 PDT
Regressed between r35231 and r35249, <http://trac.webkit.org/projects/webkit/changeset/35245> is the only suspicious revision in this range.

This is related to the fact that "/=" can be either a beginning of a regexp, or a "divide and assign" operation.  It's not necessary to escape '=' at positions other than the very beginning of a regexp.
Comment 3 Will Moffat 2008-07-23 08:47:02 PDT
To put the bug into context, it breaks all sites which do JsonP using jQuery

http://code.jquery.com/nightlies/jquery-nightly.js (grep for jsre)
Comment 4 Oliver Hunt 2008-07-24 00:38:18 PDT
Ah, whoops, it's fairly obvious just by looking at the diff, spot the error:
-                                            $$ = createNodeFeatureInfo<ExpressionNode*>(new RegExpNode(GLOBAL_DATA, "=" + l.pattern(), l.flags()), 0);
+                                            RegExpNode* node = new RegExpNode(GLOBAL_DATA, l.pattern(), l.flags());
+                                            int size = l.pattern().size() + 2; // + 2 for the two /'s
+                                            SET_EXCEPTION_LOCATION(node, @1.first_column, @1.first_column + size, @1.first_column + size);
+                                            $$ = createNodeFeatureInfo<ExpressionNode*>(node, 0);

Will fix shortly.
Comment 5 Oliver Hunt 2008-07-24 03:17:44 PDT
Committing to http://svn.webkit.org/repository/webkit/trunk ...
	M	JavaScriptCore/ChangeLog
	M	JavaScriptCore/kjs/grammar.y
	M	LayoutTests/ChangeLog
	A	LayoutTests/fast/js/regexp-divequal-expected.txt
	A	LayoutTests/fast/js/regexp-divequal.html
	A	LayoutTests/fast/js/resources/regexp-divequal.js
Committed r35323