Docstrings display broken for dataclasses

[ARF1]

Environment data

• Language Server version: 2020.11.371526539
• OS and version: Windows 10
• Python version (& distribution if applicable, e.g. Anaconda): Miniconda Python 3.9

Actual behaviour

Docstrings of dataclasses are not show for class instantiation:

You should attach the class docstring to your internally synthesized __init__ function.

Expected behaviour

Display docstrings for dataclass instantiation like you already do for normal classes:

[erictraut]

Thanks for the suggestion.

Pylance doesn't display class docstrings for constructors in any class, so this issue isn't specific to dataclasses. I guess it's more of an issue with dataclasses because the constructor is implicit.

Maybe Pylance should always display the class docstring if the constructor (__init__ or __new__ method) has no docstring. Needs more thought & discussion.

[ARF1]

Maybe Pylance should always display the class docstring if the constructor (__init__ or __new__ method) has no docstring. Needs more thought & discussion.

FWIW This suggestion gets a definite yes from me. If a programmer has made the effort of actually writing a docstring, it should be displayed if it is even remotely relevant.

I cannot imagine a single instance where a programmer did not write a docstring for their constructor because they explicitly did not want a docstring to be displayed for the constructor. It simply means that they are lazy and felt that they explained everything in the class docstring.

And if a unicorn programmer should exist that explicitly does not want any docstring being shown for their constructor, they can always write an empty docstring for their constructor.

[savannahostrowski]

We've changed the behaviour so that we display the docstring as you described above.

[ARF1]

@savannahostrowski That's great. Many thanks!

[Antyos]

@savannahostrowski Was this change included in Pylance v2021.6.1 or has it not been released yet?

I can repeat the example you showed above, but I cannot get the class docstring to appear if the __init__() docstring is not present.

Additionally, no docstrings will show up in the constructor if the class is decorated as @dataclass:

[jakebailey]

You're right, it doesn't work.

I mistakenly tested with the "expected behavior" snippet in the original issue, which was of course a simulation of what was expected.

[erictraut]

This will be fixed in the next release.

[bschnurr]

This issue has been fixed in version 2021.6.2, which we've just released. You can find the changelog here: https://github.com/microsoft/pylance-release/blob/main/CHANGELOG.md#202162-16-june-2021