Import sorting deletes comments

[andersk]

(This is a known limitation mentioned in #465 (comment), but might as well be tracked as an issue.)

ruff --select=I --fix incorrectly transforms

# preserved
import os  # deleted

# deleted
import third_party  # deleted

into

# preserved
import os

import third_party

[charliermarsh]

I don't understand isort's comment behavior yet, trying to make sense of it.

Before:

# Comment 1
# Comment 2
import D

# Comment 3a
import C
# Comment 3b
import C

import B  # Comment 4

# Comment 5

# Comment 6
from A import (
	a,  # Comment 7
	b,
	c,  # Comment 8
)
from A import (
	a,  # Comment 9
	b,  # Comment 10
	c,  # Comment 11
)

After:

# Comment 1
# Comment 2
import B  # Comment 4

# Comment 3b
# Comment 3a
import C
import D

# Comment 6
from A import a  # Comment 9
from A import b  # Comment 10
from A import c  # Comment 11

# Comment 5

[charliermarsh]

I'll just try to come up with something reasonable that does the right thing in the common cases (comment at end-of-line, etc.).

[charliermarsh]

Gonna try to fix this today. I've added comment extraction, now I just need to figure out the preservation strategy.

[tiangolo]

Amazing! This is one of the two things not allowing me to switch to Ruff's sorting, I need to preserve some comments for some # type: ignore and things like that.

[charliermarsh]

This took longer than expected. I'm not super happy with the amount of code required to handle comments, but the output is looking pretty good.

Here's the diff on Zulip:

Here's the diff on FastAPI: