Getting Invalid "type: ignore" comment reports from 3rd party library code

[Fogapod]

Bug Report

3rd party library I am using recently added pyright style type: ignore comments. I have no control on those. Example: https://github.com/Rapptz/discord.py/blob/1c4dca431db375a24820abd23f91796dcf01ad32/discord/app_commands/namespace.py#L124

For some reason mypy complains about these instead of analyzing my code. Shouldnt bad comments in 3rd party code be treated as just type: ignore?

To Reproduce

1. python -m venv .venv && source .venv/bin/activate
2. pip install mypy 'git+https://github.com/Rapptz/discord.py@a909c1ff069b1bdb332b7f3b01ef1c4b8a3a3a15'
3. create file main.py:

import discord

1 + "2"

4. mypy main.py

Expected Behavior

mypy should report errors in my code

Actual Behavior

mypy ignores errors in my code and instead complains about bad type: ignore comments in 3rd party library.

.venv/lib/python3.10/site-packages/discord/client.py:799: error: Invalid "type: ignore" comment
.venv/lib/python3.10/site-packages/discord/client.py:1162: error: Invalid "type: ignore" comment
Found 2 errors in 1 file (errors prevented further checking)

Only if I remove import discord line, mypy reports error in file.

Your Environment

• Mypy version used: 0.931
• Mypy command-line flags: none
• Mypy configuration options from mypy.ini (and other config files): none
• Python version used: 3.10.2
• Operating system and version: Arch Linux

[hauntsaninja]

Agreed that this isn't a great user experience. mypy treats invalid type ignore comments like it would syntax errors. Maybe we should make these non-blocking, so a per-module ignore_errors could work.

What do you mean by pyright-style type ignore comments? Is there a reference for that?

Your best workaround for now is something like:

[mypy-discord.*]
follow_imports = skip

[erictraut]

I think that "pyright-style" is meant to imply "a form that pyright accepts".

Since PEP 484 isn't very specific about what forms of # type: ignore are accepted, I made some (somewhat arbitrary) assumptions when implementing the support in pyright. In particular, I accept any comment starting with # type: ignore as a valid ignore comment. Anything after the # type: ignore is effectively ignored by pyright. This allows for additional information that may be interpreted by other tools such as # type: ignore; noqa or # type: ignore[misc]. It also allows for additional human-readable comments like type: ignore -- Key is there. This library is apparently taking advantage of the latter.

I think we have a couple of options here:

1. Mypy could be updated so it's "looser" in how it interprets # type: ignore comments.
2. We could agree on a "tighter" specification, and pyright (and other type checkers) could enforce that specification.

I don't have a strong opinion, but I have a slight preference for option 1 because I think there's utility in allowing additional information after the # type: ignore comment.

[hauntsaninja]

Note that mypy allows the # type: ignore # Key is there syntax mentioned in PEP 484 for additional human-readable comments. If you're coming here as an author of discord.py, I'd encourage use of this style. Since it's mentioned in PEP 484, it's likely to work with all type checkers and should help avoid confusion with things like type ignore error codes.

Changing mypy to be less strict here makes sense to me; user intention is clear modulo typos like # type: ignore[misc. Certainly not worth a blocking error like it is right now.

[hauntsaninja]

I fixed half of this (that it's a blocking error) in #13506. Let's track other half (hide parsing errors from 3rd party better) at #12162