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

首先追蹤提案中討論的 sys.monitoring PY_RETURN 回呼和插樁結構。將其與現有的 debugger return 命令進行比較，然後確定如何使用回呼提供的值取代待處理的回傳值。完成的標準是：該行為已完成規格定義、實作，並且已有測試涵蓋函式回傳值的修改。