Update __init__ return typing to be consistent

[Harshal6927]

PR Checklist

• Have you followed the guidelines in CONTRIBUTING.md?
• Have you got 100% test coverage on new code?
• Have you updated the prose documentation?
• Have you updated the reference documentation?

[Goldziher]

Ok, if we want to go this path we should actually use the NoReturn type in all init methods.

[peterschutt]

Ok, if we want to go this path we should actually use the NoReturn type in all init methods.

Mypy doesn't let you do that:

src/worker/parse.py:14: error: The return type of "__init__" must be None  [misc]
Found 1 error in 1 file (checked 92 source files)

Seems NoReturn is for functions that can never return, e.g., always raise:

Special type indicating that a function never returns.

Some refs:

• Allowing typing.NoReturn as a return hint for __init__ methods python/mypy#10342 (comment)
• False negatives with __init__ and NoReturn. microsoft/pyright#3188 (comment)

[Goldziher]

Aight

[Harshal6927]

I added return type because initializer of MakoTemplateEngine class have None as an return type. It is for the constancy.

[peterschutt]

@Harshal6927 why don't we broaden this PR out and annotate the return for all __init__() methods that need it, at least that way we are consistent everywhere:

[Harshal6927]

@Harshal6927 why don't we broaden this PR out and annotate the return for all __init__() methods that need it, at least that way we are consistent everywhere:

Should I do it?

[peterschutt]

Should I do it?

I think so, best to be consistent.

And pep recommended:

(Note that the return type of __init__ ought to be annotated with -> None. The reason for this is subtle. If __init__ assumed a return annotation of -> None, would that mean that an argument-less, un-annotated __init__ method should still be type-checked? Rather than leaving this ambiguous or introducing an exception to the exception, we simply say that __init__ ought to have a return annotation; the default behavior is thus the same as for other methods.)

[Harshal6927]

@peterschutt Ok I'll update my PR.

[jonadaly]

You missed a few __init__ definitions - could you do a quick search through the project for def __init__( and check you have got them all?

e.g.

• app.py line 180
• asgi.py line 71
• response.py line 41, 115

...etc (there are quite a few more)

[Goldziher]

@all-contributors add @Harshal6927 code

[allcontributors]

@Goldziher

I've put up a pull request to add @Harshal6927! 🎉