Bug 272199 – Web Inspector: JavaScript breakpoint location is sometimes incorrect when inspector first shows up

• Status: RESOLVED
• Resolution: WORKSFORME
• Component: Web Inspector

[Qianlang Chen]

Created attachment 470762 [details]
Video demo: Breakpoint location is incorrect unless I click on the breakpoint

If you set a breakpoint in some file at line L and column C, sometimes when that breakpoint first shows up in the source side bar on the left, the source location is displayed as 1:(global C ignoring new lines) instead of L:C.

To reproduce (this is only one instance that the issue may reproduce, but it can happen on any website and any source file):
   1. Go to https://search.brave.com
   2. Open inspector's Sources tab
   3. Make a breakpoint in the 0.DS3i2RRo.js file at line 5
   4. Try reloading the page with the inspector open, navigating to another page and go back, reopening the inspector, and/or all of the above, to make the bug show up
      - Due to https://bugs.webkit.org/show_bug.cgi?id=272098 sometimes the breakpoint just doesn't show up in the sidebar. Change the file filter from "By Type" or "By Path" to the other one if it doesn't show up
      - When the bug happens, the breakpoint's location shows up as some 1:1507 instead of 22:9

See video demo. As you can see, the bug doesn't always happen.

[Radar WebKit Bug Importer]

<rdar://problem/125938900>

[Qianlang Chen]

Update: The reason the breakpoint shows up as 1:1507 by default is because the source file 0.DS3i2RRo.js is "minified" and unformatted where all the code is on one line. Our inspector by default turns on a feature to prettify the code opened in the source editor, and that's what puts the breakpoint at 22:9 when I created it.

The inspector is behaving correctly since the breakpoint in the unformatted file does belong to location 1:1507.

[Qianlang Chen]

Also, the reason in the original bug description that the bug doesn't always happen is because I didn't highlight/select the source file 0.DS3i2RRo.js when I reloaded the inspector, so the source editor didn't show that source file so therefore didn't get to prettify it to have a different source location. Looking at it this way means it's also behaving expectedly and not flakily.

Although, maybe this still shows that the behavior is somewhat confusing as I clearly didn't know this either before having investigating closely.