gh-137477: Fix inspect.getblock() for generator expressions

[serhiy-storchaka]

This fixes also inspect.getsourcelines() and inspect.getsource().

• Issue: inspect.getsourcelines() mishandles multi-line generator expressions #137477

[gaogaotiantian]

Could you explain this part a bit to me? What's in the else case? Why is islambda set? I was a bit confused (without testing too much into it) when I read the code because I thought this is definitely not a lambda here.

[serhiy-storchaka]

For def and class we search to the end of the block. For lambda and generator expressions we search to the end of the logical line. self.islambda is used to distinguish between these modes. We could rename it, but this will increase the size of the diff and may break user code that uses this private class, so I leave it for a time.

Although the code can be simplified.

[serhiy-storchaka]

@gaogaotiantian, is it fine to you?

[gaogaotiantian]

Sorry I've been travelling the world so not super responsive. Even though I always agree a minimum change is preferred, but islambda is still very confusing to me. I know you added a comment, but that does not make it super clear - the logic between generator and lambda is still vague. Let's say in the future we somehow have a third case, do we still call it islambda? I think we should give it a better name now, a name that actually represents what it means - end at logic line instead of the end of block.

This could raise some minor backwards compatibility issues, I agree. I think it can be ignored because it's a non-documented variable in a private class. Another way is to add another variable isgenerator, which will fix the issue, keep the backwards compatibility but make the diff even larger.

If the breaking change is really a huge concern to you, I think I can accept a backport with this change, and an immediate rename for main, will that be a good compromise that you think is proper?

[serhiy-storchaka]

What name would be good? singleline? logicalline? singlelogicalline? multiline=False?

Anyway, I want to refactor this code in main. There is no justification to use a class -- it may be a simple function taking a stream of tokens.