`inspect.getsourcelines()` mishandles multi-line generator expressions

[George-Ogden]

Bug report

Bug description:

import inspect

def source_error(*args):
    frame = inspect.currentframe()
    if frame is None:
        return
    frame = frame.f_back
    if frame is None:
        return
    print(inspect.getsource(frame))

def demo():
    loops = (
        None for _ in [0] if source_error(True)
    )
    list(loops)

demo()

Expected output:

def demo():
    loops = (
        None for _ in [0] if source_error(True)
    )
    list(loops)

Actual output:

    loops = (

CPython versions tested on:

CPython main branch

Operating systems tested on:

Linux

Linked PRs

• gh-137477: Extend regex pattern check in inspect.findsource #137479
• gh-137477: Fix inspect.getblock() for generator expressions #137488

[George-Ogden]

Possibly related to #122981
Introduced in #117025

[AA-Turner]

cc @gaogaotiantian

[serhiy-storchaka]

I do not think that restoring that regexp is a correct solution. This method has proven unreliable. And even if it works, it will show the source of the first function or class above the generator expression. It may even not include the source of the generator expression.

I think that the right method is to fix getblock(), so it will process generator expressions similarly to lambda expressions.