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

首先跟踪提案中讨论的 sys.monitoring PY_RETURN 回调和插桩结构。将其与现有的 debugger return 命令进行比较，然后确定如何使用回调提供的值替换待处理的返回值。完成的标准是：该行为已完成规范定义、实现，并且已有测试覆盖函数返回值的修改。