273254 2024-04-25 10:47:21 -0700 [Yarr] Regex Lookbehinds differs from v8 2024-05-16 08:02:13 -0700 1 1 1 Unclassified WebKit JavaScriptCore Safari Technology Preview Unspecified Unspecified RESOLVED FIXED https://bugs.webkit.org/show_bug.cgi?id=174931 BrowserCompat, InRadar P2 Normal --- 1 dylan.conway567 msaboff karlcow mark.lam mike msaboff webkit-bug-importer ysuzuki oldest_to_newest 2031207 0 dylan.conway567 2024-04-25 10:47:21 -0700 The following text and regex will fail to replace. Using v8 it will match and replace successfully. ``` console.log("<TData = SettingsControllerGetAllResponse>(".replace(/(?<=TData = |<)(\w+(?:Error|Response))/g, "foo")); ``` Received output: "<TData = SettingsControllerGetAllResponse>(" Expected output: "<TData = foo>(" This example is minified from: https://github.com/oven-sh/bun/issues/10508 2032825 1 webkit-bug-importer 2024-05-02 10:48:52 -0700 <rdar://problem/127440248> 2035498 2 karlcow 2024-05-15 01:35:27 -0700 Thanks for the report. I can confirm the output. string: "<TData = SettingsControllerGetAllResponse>(" then .replace( /(?<=TData = |<)(\w+(?:Error|Response))/g, "foo" ) 2035499 3 karlcow 2024-05-15 01:39:54 -0700 This gives the proper result in both Firefox and Chrome. 2035501 4 karlcow 2024-05-15 01:51:14 -0700 (?<=TData = |<)(\w+(?:Error|Response))> This one is working, aka just adding ">" at the end. 2035504 5 karlcow 2024-05-15 02:00:36 -0700 OK Just adding a Z on Error is making it work. (?<=TData = |<)(\w+(?:ErrorZ|Response)) It seems there's a minimum size required on the strings to match set to 6 characters. We can see that with (?<=TData = |<)(\w+(?:Respo)) FAIL (?<=TData = |<)(\w+(?:Respon)) PASS 2035505 6 karlcow 2024-05-15 02:02:42 -0700 This? const size_t thresholdForBinarySearch = 6; https://searchfox.org/wubkat/rev/7051b8f5cd90af80f03a58d74741cdb04c800b6e/Source/JavaScriptCore/yarr/YarrInterpreter.cpp#520 2035506 7 karlcow 2024-05-15 02:05:28 -0700 There is no threshold for Firefox and Chrome This is working for example. (?<=TData = |<)(\w+(?:R)) 2035571 8 msaboff 2024-05-15 09:56:18 -0700 Currently working on this bug. This issue is not the length itself of the lookbehind, but the lookbehind length relative to the remaining expression's minimum length. 2035685 9 msaboff 2024-05-15 20:43:16 -0700 Pull request: https://github.com/WebKit/WebKit/pull/28641 2035795 10 ews-feeder 2024-05-16 08:02:11 -0700 Committed 278863@main (fafab4133900): <https://commits.webkit.org/278863@main> Reviewed commits have been landed. Closing PR #28641 and removing active labels.