[debug] Is StackTraceResponse.totalFrames truly necessary?

[vadimcn]

The description of supportsDelayedStackTraceLoading debug adapter capability stipulates that in order for delayed stack loading to work, the adapter must populate the totalFrames field of StackTraceResponse.

However, for native debuggers, this value is not so easy to compute. For example, when FPO (frame pointer omission) optimization is in play, the debugger may need to load debug info for all modules currently on stack, even those at the very bottom which the user probably didn't care about.

Since the total number of frames is never surfaced in the UI, I am wondering whether totalFrames is truly necessary. Wouldn't VSCode know that it has reached bottom of the stack when it receives back less frames than the levels it requested?

[weinand]

Valid question. We will discuss this...

@isidorn you don't need this, right?

[isidorn]

Yes that is correct. However keep in mind the following case:
There are exactly 20 frames: vscode gets all of them since we fetch 20 and display the "load more stack frame" button. If the user clicks on that button no more frames will be loaded (since we already fetched all) -> just that button will disapear.

I am fine with this corner case, but just to be aware of it.

[vadimcn]

And if anyone does care, you could ask for 21 frames, but display 20.

[isidorn]

@weinand do we want to do something here? Assigning to November and debt so we discuss.