Enabling FormatOnSave with Black makes saving files impossible

[tomkcook]

Type: Bug

Open workspace settings and enable "FormatOnSave".

Open a Python file and configure Black as the default formatter.

Make a change and attempt to save the file.

Every time I try to save a file, VScode pops up a note that the file has changed on disk and do I really want to overwrite the change?

This only affects Python files formatted with Black. I assume the Black formatter is being run on the file in the background before saving the file and this results in the file being changed on disk, which VScode then fails to reload correctly.

Extension version: 1.0.3
VS Code version: Code 1.86.1 (31c37ee8f63491495ac49e43b8544550fbae4533, 2024-02-07T09:07:19.849Z)
OS version: Linux x64 6.6.10-060610-generic
Modes:

System Info

Item	Value
CPUs	13th Gen Intel(R) Core(TM) i9-13900HX (32 x 3205)
GPU Status	2d_canvas: enabled canvas_oop_rasterization: disabled_off direct_rendering_display_compositor: disabled_off_ok gpu_compositing: enabled multiple_raster_threads: enabled_on opengl: enabled_on rasterization: enabled raw_draw: disabled_off_ok skia_graphite: disabled_off video_decode: enabled video_encode: disabled_software vulkan: disabled_off webgl: enabled webgl2: enabled webgpu: disabled_off
Load (avg)	1, 1, 1
Memory (System)	31.15GB (11.25GB free)
Process Argv	. --crash-reporter-id b8a9e683-f4ee-415b-9c94-a32686cb170e
Screen Reader	no
VM	0%
DESKTOP_SESSION	gnome
XDG_CURRENT_DESKTOP	GNOME
XDG_SESSION_DESKTOP	gnome
XDG_SESSION_TYPE	x11

A/B Experiments

vsliv368:30146709
vspor879:30202332
vspor708:30202333
vspor363:30204092
vstes627:30244334
vscod805cf:30301675
binariesv615:30325510
vsaa593cf:30376535
py29gd2263:30899288
vscaac:30438847
c4g48928:30535728
azure-dev_surveyone:30548225
962ge761:30959799
pythongtdpath:30769146
welcomedialogc:30910334
pythonidxpt:30866567
pythonnoceb:30805159
asynctok:30898717
pythontestfixt:30902429
pythonregdiag2:30936856
pyreplss1:30897532
pythonmypyd1:30879173
pythoncet0:30885854
pythontbext0:30879054
dsvsc016:30899300
dsvsc017:30899301
dsvsc018:30899302
pydisww2:30959801
7j2b6412:30962116
bg6jg535:30958357

[34j]

Please consider using Auto Save instead of Format On Save. This extension sells the simplicity of calling black in the CLI. You should also consider using Microsoft's extension, which goes more into the internals of VS Code, which seems to be required to resolve this issue. Thanks for your report anyway.
(BTW, what is A/B Experiments? It looks cool.)