Link to mypy's error code documentation

[Avasam]

Closes #57

I wish there was a better way to map code to url for maintainability, I have opened a doc feature request with mypy to have better way to programmatically link to the codes' doc. Both for better anchors and a way that doesn't span 2 pages. python/mypy#15431

Demo:

Which links to https://mypy.readthedocs.io/en/latest/_refs.html#code-import

Other potential improvements:

• We could link to a specific mypy version doc instead of "stable/latest". But I don't it would bring much value anyway.
• After the next mypy release, "latest" can be changed to "stable".

[karthiknadig]

Thanks for the PR 🥳

I have some minor changes. I think we can directly return a CodeDescription from the helper function. That would also mean that the case where we don't have a link will give the same old result as before.

[karthiknadig]

@Avasam Looks like there is a formatting issue. Can you run black on lsp_utils.py?

[Avasam]

With python/mypy#15435 and python/mypy#15437, up to you if you wanna update the logic in a separate PR or wait for the next mypy release so we can point to stable in this PR using consistent anchors.

Or an in-between: point to latest for now.

[karthiknadig]

@Avasam We can point to the latest. With the assumption that the error messages are not going to change significantly.

[Avasam]

Sorry to do an update after an approval, but this is much more maintainable.