Incorrect/misleading error message for zip

[ldorigo]

Issue Type: Bug

Consider the following three functions (I've tried to remove as much unnecessary code as possible):

def get_vocab_from_file(vocab_name: str) -> Iterator[str]:
    for line in ["test_1","test_2","test_3"]:
        yield line.strip()

def get_samples_from_vocab(
    vocab: List[str], amount: int, exclude: Optional[List[str]] = None
) -> List[str]:
    candidates: List[str]
    while True:
        candidates = random.sample(vocab, amount)
        if not exclude or not any([candidate in exclude for candidate in candidates]):
            break
    return candidates

def create_neg_samples_test_file(vocab_name: str, amount: int = 5000):
    test_name = vocab_name + "_neg_samples"
    
    vocab = get_vocab_from_file(vocab_name)
    endless_vocab = itertools.cycle(vocab)
    vocab_rightsize = more_itertools.take(amount, endless_vocab)

    random_pairs = zip(
            vocab_rightsize,
            get_samples_from_vocab(vocab, amount),
        )
    # ...

The above code is wrong: get_samples_from_vocab expects a List[str] as first argument, while I am giving it an Iterator[str]. But this is what pylance shows me:

If I hover random pairs, the error message is:

Fair enough. If I hover any other part of the expression to learn more, however, I get this:

Which doesn't make sense (List[str],List[str] is a perfectly valid signature for the arguments of zip).

It's only if I hover on vocab that I get the actual error that appears to be causing the other ones:

And indeed, if I fix it that problem, the other errors go away:

Extension version: 2021.8.3-pre.1
VS Code version: Code 1.59.1 (3866c3553be8b268c8a7f8c0482c0c0177aa8bfa, 2021-08-19T11:54:37.513Z)
OS version: Linux x64 5.10.56-1-lts
Restricted Mode: No

System Info

Item	Value
CPUs	AMD Ryzen 7 3700X 8-Core Processor (16 x 4226)
GPU Status	2d_canvas: enabled gpu_compositing: enabled multiple_raster_threads: enabled_on oop_rasterization: disabled_off opengl: enabled_on rasterization: disabled_software skia_renderer: enabled_on video_decode: disabled_software vulkan: disabled_off webgl: enabled webgl2: enabled
Load (avg)	3, 2, 2
Memory (System)	31.36GB (2.91GB free)
Process Argv	--crash-reporter-id 66ea3ec9-05eb-4edd-8d35-34bbe6c1aba1
Screen Reader	no
VM	0%
DESKTOP_SESSION	plasma-i3
XDG_CURRENT_DESKTOP	KDE
XDG_SESSION_DESKTOP	KDE-i3
XDG_SESSION_TYPE	x11

[erictraut]

Could you include the diagnostic message that you're seeing from pylance?

Also, it would be helpful if you could provide a sample that is a self-contained and minimal repro case. The code above is incomplete and includes symbols that are not defined. For example, I can't tell where the local variable vocab is being assigned a value.

[ldorigo]

Sorry, I am still writing the issue. Vscode started posting issues directly on github instead of preparing them in preview mode so it got posted before I was done...

[ldorigo]

Is it good enough now? I tried removing anything that isn't related to the issue or that depends on external code, and added back the assignment for vocab that got lost on the way. Let me know if there are other problems.

[erictraut]

Thanks for the bug report. I agree that this error message is confusing and unnecessary. I've modified the logic to eliminate it. This change will be in the next release.

[heejaechang]

the fix is in 2021.8.3 release.