Invalid syntax output for modules that directly import __future__

[adamchainz]

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Given this example.py:

import __future__


print(__future__.all_feature_names)

Run isort with --add-import and a future import:

$ isort --add-import 'from __future__ import annotations' example.py
Fixing /Users/chainz/tmp/example.py

…gives:

import __future__
from __future__ import annotations

print(__future__.all_feature_names)

This file is invalid syntax:

$ python example.py
  File "/Users/chainz/tmp/example.py", line 2
    from __future__ import annotations
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
SyntaxError: from __future__ imports must occur at the beginning of the file

A workaround is to use if True, so isort puts the imports like so:

from __future__ import annotations

if True:
    import __future__

print(__future__.all_feature_names)

But ideally isort would special case __future__ and sort the from imports before the module import:

from __future__ import annotations
import __future__


print(__future__.all_feature_names)