isort removes newlines before standalone comments if the following line is an import of the same group

[gaborbernat]

Operating system: Arch Linux
Python version: Python 3.6.6
Black version: 18.5b0
Does also happen on master: yes

Given:

import a
# noinspection PyProtectedMember
import _a

Black formats this to (note the introduced empty line):

import a
# noinspection PyProtectedMember

import _a

However isort correctly (in the recommended mode 3) formats it to:

import a
# noinspection PyProtectedMember
import _a

[ambv]

Black puts an empty line after every group of imports. A standalone comment signifies an end of a group of imports before it.

So, your example is wrong, Black will do this instead with the original file:

--- /tmp/asd.py  (original)
+++ /tmp/asd.py  (formatted)
@@ -1,4 +1,5 @@
 import a
+
 # noinspection PyProtectedMember
 import _a

The behavior between isort and Black is indeed different here. I haven't decided yet how to resolve this.

[gaborbernat]

Thanks for the explanation, would be nice to somehow support this use case though.

[skorokithakis]

I am affected by this as well :/ Just to clarify, what is the problem here? Is Black wrong, or is isort? Is the newline supposed to be there?

[gaborbernat]

@ambv any plans to address this? This makes the line of This also makes Black compatible with isort with the following configuration. from the readme not entirely true. And the only solution in the meantime is to remove such comments, which is not good generally. I get that black does not want to venture into the business of import ordering; but in that case it should play nice with tools out there that do this task, e.g. isort. I personally would place this as a pretty critical bug; not enhancement per se. If there's a decision on this maybe we (the community) can try to create a PR, but for that, we would need to discuss what a solution would be.

[tibz7-zz]

I'm also affected. what is the current status about this bug?

[thisfred]

I think black is being too prescriptive here: yes comments between imports can be used as headers, but they can also be things like:

import a
# XXX: unused import, that however shouldn't be removed 
# because our framework depends on it being present
import b