option no-implicit-optional ignored as inline configuration and per-module flags

[fnep]

I found a potential bug (not sure) with mypy 0.740 and Python 3.6.5 & Python 3.7.1.

The following code:

# mypy: no-implicit-optional

def add(self, a: int, b: int = None) -> int:
    return a + b

… gives me

run.py:4: error: Unsupported operand types for + ("int" and "None")
run.py:4: note: Right operand is of type "Optional[int]"

… but I would expect to get the more clear

run.py:3: error: Incompatible default for argument "b" (default has type "None", argument has type "int")

… because the inline config "no-implicit-optional" is set. It is the same if I have a per file/moule section in my mypy.ini, but it works i if define it globally (in [mypy] section) or via command line switch.

[ilevkivskyi]

Hm, interesting. It seems to me this may be related to #7773. In particular, it seems to me logic of definition of --no-implicit-optional in mypy/main.py should match that of --no-warn-no-return.

Also this is one of only two flags that have no_ prefix in mypy/options.py and both suffer from #7773.

[MrRaval17]

@ilevkivskyi I was able to reproduce the scenario mentioned by @efenka :

I also saw #7773 issue. I guess the "unrecognized options" error is being produced because the options which cause those errors are not defined in mypy/options.py or are defined with different names ?

However I don't understand what you meant by this:

In particular, it seems to me logic of definition of --no-implicit-optional in mypy/main.py should match that of --no-warn-no-return

Did you mean to change line 548 in mypy/main.py:
add_invertible_flag('--no-implicit-optional', default=False, strict_flag=True, help="Don't assume arguments with default values of None are Optional", group=none_group)

to match line 570 in mypy/main.py:

add_invertible_flag('--no-warn-no-return', dest='warn_no_return', default=True, help="Do not warn about functions that end without returning", group=lint_group)

[davidzwa]

@ilevkivskyi I saw your comment on no_* settings. I'm involved in the --no-site-packages issue #7768 (PR: #8524) and to do that I've added no_site_packages to options.py. I suspect if your intuition comes out to be true, my contribution there might influence it.

I will look into this issue further Wednesday, so any other information might come in handy.

[srbhss]

Hey @ilevkivskyi, I would like to work on this issue. Please assign me this one.

[ilevkivskyi]

@srbhss OK, note however I may not have time to review your PR, but others might have.

[odesenfans]

This issue appears to be fixed in mypy 0.961.

[hauntsaninja]

Looks like it got fixed a long time ago, somewhere between 0.780 and 0.790