Step into worker broken on macOS

• Debug the web-worker-ts demo
• Break on the new Worker line, press step in
• It doesn’t break in the worker

Works on linux. This is why cross thread constructor source map is failing on mac.

On Linux there is an extra Debugger.paused event fired before the worker is loaded, which has the asyncCallStackTraceId that we need to pause when the worker is loaded. This isn’t sent on mac. Chrome bug right, or do you see anything else?

ww-mac.txt ww-linux.txt

[connor4312]

Chatting with @dgozman:

Connor Peet One kind of ugly idea I had was to stash the last call frame we saw before stepping in, and then looking for that frame in the async stack of pause events to see if we got here from an async step.

​Dmitry Gozman I see the problem, let me think a bit

Dmitry Gozman Your solution seems ok for now, but I’d suggest to compare all call frames up to asyncStackTraceId to be on the safe side.

Dmitry Gozman The right fix would be to change v8 to emit “ambiguous” pause reason with both “instrumentation” and “asyncStep”. I can do that soon-ish, but it will take time to reach stable Chrome version

This scenario is an edge case, and the call frame implementation would add a moderate amount of complexity to an already fairly complex scenario. Additionally, there is a workaround to manually set a breakpoint on the first line of the worker file. Therefore I would prefer to leave this as-is awaiting the upstream fix, unless we get user feedback that this is problematic for them.

[roblourens]

That’s fine with me. Debugging workers at all is totally new so we aren’t losing anything.