Auto-format adds and removes a semi-colon

[ripperdoc]

Issue Type: Bug

I haven't succeeded in creating a complete reproduction of this issue. What happened is this: as I was editing a source file, I noticed that every time I saved, an additional semi-colon was added after a function. At some point it would create one new semicolon after each save, stacking them up and generating syntax error. Currently, it just switches between adding an extra semi-colon, and then removing it on next save.

This only appears on a particular function. I have Prettier as formatter, but this error doesn't happen if I run Prettier separately from the command pallette, only when saving. I checked the Format on Save settings and the error only appears if set to modifications or modificationsIfAvailable, not on full. So this tells me the error happens because some interplay between the change in this file vs what's in Git. Maybe the diff that extracts only the modified lines plays poorly with the Prettier formatter?

If I copy the same code to another file, the issue doesn't appear, which makes sense as there is not Git history for it to use. I can send the full before and after source if needed but I would prefer to keep it private. See below for a screencap in diff mode when I save several times, it adds and then removes and then adds semicolon.

Screen.Recording.2022-04-06.at.13.49.36.mov

VS Code version: Code 1.66.0 (e18005f, 2022-03-30T05:50:04.419Z)
OS version: Darwin x64 18.7.0
Restricted Mode: No

System Info

Item	Value
CPUs	Intel(R) Core(TM) i7-3720QM CPU @ 2.60GHz (8 x 2600)
GPU Status	2d_canvas: enabled canvas_oop_rasterization: disabled_off direct_rendering_display_compositor: disabled_off_ok gpu_compositing: enabled metal: disabled_off multiple_raster_threads: enabled_on oop_rasterization: enabled opengl: enabled_on rasterization: enabled raw_draw: disabled_off_ok skia_renderer: enabled_on video_decode: enabled video_encode: enabled webgl: enabled webgl2: enabled
Load (avg)	3, 3, 3
Memory (System)	16.00GB (0.39GB free)
Process Argv	--crash-reporter-id f38762bb-c266-463a-bc0c-77d8ce21e900
Screen Reader	no
VM	0%

Extensions (39)

Extension	Author (truncated)	Version
better-toml	bun	0.3.2
vscode-svgviewer	css	2.0.0
vscode-eslint	dba	2.2.2
unity-debug	dei	3.0.11
gitlens	eam	12.0.5
vscode-front-matter	eli	7.0.0
prettier-vscode	esb	9.5.0
php-intellisense	fel	2.3.14
foam-vscode	foa	0.17.8
vscode-nginx-conf-hint	han	0.3.0
vscode-mocha-test-adapter	hbe	2.13.3
vscode-test-explorer	hbe	2.21.1
vscode-edit-csv	jan	0.6.8
vscode-styled-components	jpo	1.7.0
vscode-gutter-preview	kis	0.30.0
vscode-markdown-notes	kor	0.0.24
nodejs-repl	los	0.5.15
AWK	lug	0.0.2
rainbow-csv	mec	2.2.0
vscode-docker	ms-	1.21.0
csharp	ms-	1.24.3
python	ms-	2022.4.0
vscode-pylance	ms-	2022.3.4
jupyter	ms-	2022.3.1000901801
jupyter-keymap	ms-	1.0.0
jupyter-renderers	ms-	1.0.6
hexeditor	ms-	1.9.5
test-adapter-converter	ms-	0.1.5
autodocstring	njp	0.6.1
view-in-browser	qin	0.0.5
vscode-coverage-gutters	rya	2.9.1
jinjahtml	sam	0.17.0
markdown-link-expander	skn	0.2.1
rewrap	stk	1.16.3
markdown-links	tch	0.8.0
shellcheck	tim	0.19.0
vscode-counter	uct	3.0.3
php-debug	xde	1.25.0
markdown-all-in-one	yzh	3.4.0

(2 theme extensions excluded)

A/B Experiments

vsliv368cf:30146710
vsreu685:30147344
python383cf:30185419
vspor879:30202332
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vspor363:30204092
pythonvspyl392:30443607
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pythonptprofiler:30281270
vshan820:30294714
vstes263cf:30335440
vscoreces:30445986
pythondataviewer:30285071
vscod805:30301674
pythonvspyt200:30340761
binariesv615:30325510
bridge0708:30335490
bridge0723:30353136
vsaa593cf:30376535
vsc1dst:30438360
pythonvs932:30410667
wslgetstarted:30449410
pythonvsnew555:30457759
vscscmwlcmt:30465135
pynewfile477:30463512

[jrieken]

It looks like the issue is caused by one of your installed extensions. All extensions execute together on a single nodejs process, so in order to narrow down the possible problematic extension, please try the following:

• run F1 > Help: Start Extension Bisect
• (this will restart VS Code with half of your extensions disabled)
• try to do the steps which reproduce the problem
• if the problem reproduces, click "This is bad" (this narrows down the problematic extension to the half which was enabled)
• if the problem does not reproduce, click "Good now" (this narrows down the problematic extension to the half which was disabled)
• these steps will repeat until the problematic extension is found

initial	step	final

[ripperdoc]

Thanks! I've completed the Bisect and as suspected it was Prettier, but it only happens when VS Code is set to auto-format on save by "editor.formatOnSaveMode": "modificationsIfAvailable" or "editor.formatOnSaveMode": "modifications", NOT when "editor.formatOnSaveMode": "file".

[jrieken]

Thanks a great find. Closing this issue and asking you to raise it issue against prettier. Format on save with modificationsIfAvailable is technically the same as format selection, e.g it uses the same underlying API (DocumentRangeFormattingEditProvider), and when formatting results are wrong it's usually an issue with the extension