mypy confuses dataclass field name with imported function name
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Description
Bug Report
This standalone file produces the mistaken error models/mypy_bug.py:8: error: "str" not callable:
from dataclasses import dataclass, field
from typing import List
@dataclass
class FilterExpression:
match_type: str
field: str
value: List[str] = field(default_factory=list)
This is because mypy confuses the field "field" and the imported function "field()". Renaming the field removes the error message.
Expected Behavior
This should not be an error.
It's not obvious to me what's correct here, but this code executes as intended in Python 3.8.
So either mypy or Python 3.8 is wrong about this. I choose to file the bug with mypy.
Actual Behavior
mypy gives this error:
models/mypy_bug.py:8: error: "str" not callable
Your Environment
- Mypy version used: 0.800
- Mypy command-line flags: Only
--ignore-missing-imports [paths] - Mypy configuration options from
mypy.ini:strict_optional = False - Python version used: 3.8
- Operating system and version: MacOS 11.2
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start by running mypy 0.800 on the standalone models/mypy_bug.py example with the reported flags and Python 3.8 environment, then inspect the name-resolution path for dataclass fields and imported functions. Done means the example no longer reports "str" not callable while preserving correct handling of the field() default factory.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- python
- Domain
- devtools
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Clearly specified
- Newbie friendliness
- 35/100