MyPy Incorrectly Flags Module Attribute Inside Format String

Bug Report

An unexpected [attr-defined] was reported when accessing module attributes inside of a format string.

To Reproduce

1. Create a file called constants.py with contents below:

FOO = "foo"

2. Create a file called main.py with contents below:

import constants

def bar():
    # type: () -> str
    print("{foo}".format(foo=constants.FOO))
    return "{constants.FOO}".format(constants=constants)

3. run python3 -m mypy constants.py main.py

main.py:6: error: Module has no attribute "FOO"
Found 1 error in 1 file (checked 2 source files)

Expected Behavior

I expected the format string "{constants.FOO}".format(constants=constants) to not throw an error, since constants.FOO is defined.

(Write what you thought would happen.)

Actual Behavior

The line print("{foo}".format(foo=constants.FOO)) reports no error (indicating that the value FOO exists in constants, but the line "{constants.FOO}".format(constants=constants) reports an error as if it does not.

Your Environment

• Mypy version used: 0.790
• Mypy command-line flags: python3 -m mypy constants.py main.py
• Mypy configuration options from mypy.ini (and other config files): No mypy.ini used
• Python version used: Python 3.8.5 (brew installed)
• Operating system and version: MacOS Catalina 10.15.6

Inizia con il riproduttore di constants.py e main.py ed esegui python3 -m mypy constants.py main.py usando l’esempio riportato. Traccia il modo in cui viene analizzata l’espressione di formattazione, quindi verifica che l’attributo del modulo all’interno della stringa di formattazione non produca più un errore attr-defined, mentre l’accesso diretto esistente rimanga valido.