Support changing return value of a function in sys.monitoring

Feature or enhancement

Proposal:

gdb has a command return for users to immediately return from the function. It basically does two things:

1. stop the execution of the function
2. return an arbitrary value

In Python, 1. might not be that simple as we have all the references to the stack value (it should be doable, but may or may not worth it), but 2. should be pretty straightforward. We can allow the callback for PY_RETURN function to return something specific (like sys.monitoring.RETURN, retval) to replace the value we are about to return. It should only need to swap the value on the stack and the impact should be contained. Some of the instrumentation structure needs to be refactored a bit but I don't think it's too much work.

With this feature, we can "mock" the return value in the debugger. We can even expand our existing return command - we may not able to return immediately, but we can run until it returns and secretly swap the return value, so we can call this command from anywhere.

Does this sound like a reasonable feature or I'm missing something? @markshannon

Has this already been discussed elsewhere?

No response given

Links to previous discussion of this feature:

No response

Inizia tracciando il callback PY_RETURN di sys.monitoring e la struttura di strumentazione descritta nella proposta. Confronta questo con il comando di ritorno esistente del debugger, quindi determina come un valore fornito da un callback potrebbe sostituire il valore di ritorno in sospeso. Il lavoro è completato quando il comportamento è specificato, implementato e coperto da test per la modifica del valore di ritorno di una funzione.