1886201 - Debugging llm_chat.54531fa5.js from https://webllm.mlc.ai/ causes full browser hangs in layout

Status: NEW

(DevTools :: Debugger, defect, P2)

Description

[Jeff Muizelaar [:jrmuizel]]

What were you doing?

Please tell us what site you were on, and what steps led to the error you are reporting

I was trying to debug https://webllm.mlc.ai/ and single stepped into llm_chat.54531fa5.js

What happened?

The browser becomes completely unresponsive: https://share.firefox.dev/4a5ntb6
It seems like we get stuck reflowing very long lines.

What should have happened?

The browser should remain responsive

Comment 1

[Nicolas Chevobbe [:nchevobbe][PTO back September 7]]

Thanks for the report Jeff, looks like most of the time is spent in CodeMirror , which we don't have a lot of control over.
The good news is that we're in the process of migrating to the newest version, so it might help?
Just so we have the same reference, can you close the debugger if it is still open, turn devtools.debugger.features.codemirror-next to true in about:config and repeat the steps and share the profile here ? So we can see if Bug 1878647 will help

Comment 2

[Nicolas Chevobbe [:nchevobbe][PTO back September 7]]

Also, having a second look, it seems that time is spent in ColumnBreakpoint , did you set any breakpoint in the file? If not, there's probably something we can do better

Comment 3

[Jeff Muizelaar [:jrmuizel]]

I tried out devtools.debugger.features.codemirror-next and the debugger didn't really seem usable. I couldn't set/see breakpoints or see where execution currently is.

I was able to open llm_chat.54531fa5.js without hangs but it seemed to not show the long line and had weirdness around selection.

Comment 4

[Jeff Muizelaar [:jrmuizel]]

(In reply to Nicolas Chevobbe [:nchevobbe] from comment #2)

Also, having a second look, it seems that time is spent in ColumnBreakpoint , did you set any breakpoint in the file? If not, there's probably something we can do better

There should not be a breakpoint in llm_chat.54531fa5.js

Comment 5

[Julian Descottes [:jdescottes]]

As Nicolas said, considering the profile there must have been a breakpoint set at some point (maybe misclicking on the gutter or something else?).
The patch from Bug 1877574 could help here.