Remove dependency on `Debugger.CallFrame.url`

[bmeurer]

We are exploring the idea to deprecate the url field in Debugger.CallFrame, which is sent as part of Debugger.paused events. crbug/1270316 tracks this work. The motivation is that URLs can be costly (worst case we've seen so far is whole WebAssembly modules being served as Base64-encoded data:-URLs), and the information is

1. redundant, since the location.scriptId on the same CallFrame let's the debugger front-end lookup the URL from Debugger.scriptParsed events, and
2. potentially ambiguous, as the URL is not guaranteed to be unique (example of this is crbug/1270248).

Design doc with more context here.

[connor4312]

Thanks for the heads up. We do depend on the URL in a couple places right now, but also maintain a script ID mapping so we can use the location. I'll have this as a debt item for clean up in December/Janurary

[bmeurer]

Thanks for the quick response.

What I forgot to mention is that we are also exploring the possibility of deprecating Runtime.CallFrame.url, which is even more costly to maintain (especially in the context of async stack traces in huge applications). For Runtime.CallFrame.url there are plenty of uses outside of debuggers, so it'll probably turn out to be a flag to Runtime.enable to disable collecting and sending the url fields, but giving the scalability problems, it might be a good opportunity for VScode to also reduce dependencies on it.

[connor4312]

Thanks for the heads up, we should be able to drop dependency on both of those fairly easily.

[bmeurer]

Heads up, I'm about to land this CL in V8, so starting with Chromium 100, the url field of Debugger.CallFrame will contain an empty string.

[connor4312]

Good timing, I'm taking care of this this week 🙂