SCM Tab refresh on every keypress on editor

[anandbibek]

Type: Bug

The issue is reproducible when connected to remote env via SSH and there is an active SCM system recognised.

Every keypress on the editor shows the SCM tab refreshing for a split second. This also somehow makes the code completion and suggestion popups appear after that SCM refresh is done. This causes an overall delay in working with the editor and getting suggestions.

VS Code version: Code 1.77.1 (b7886d7, 2023-04-04T23:21:11.906Z)
OS version: Windows_NT x64 10.0.22000
Modes:
Sandboxed: No
Remote OS version: Linux x64 5.4.17-2136.317.5.3.el8uek.x86_64
Remote OS version: Linux x64 5.4.17-2136.317.5.3.el8uek.x86_64

System Info

Item	Value
CPUs	11th Gen Intel(R) Core(TM) i7-1185G7 @ 3.00GHz (8 x 1805)
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_renderer: enabled_on video_decode: enabled video_encode: enabled vulkan: disabled_off webgl: enabled webgl2: enabled webgpu: disabled_off
Load (avg)	undefined
Memory (System)	31.73GB (19.81GB free)
Process Argv
Screen Reader	no
VM	0%

Item	Value
Remote	SSH: anaray-dev
OS	Linux x64 5.4.17-2136.317.5.3.el8uek.x86_64
CPUs	AMD EPYC 7J13 64-Core Processor (4 x 2445)
Memory (System)	31.08GB (20.67GB free)
VM	0%

Item	Value
Remote	SSH: anaray-dev
OS	Linux x64 5.4.17-2136.317.5.3.el8uek.x86_64
CPUs	AMD EPYC 7J13 64-Core Processor (4 x 2445)
Memory (System)	31.08GB (20.67GB free)
VM	0%

Extensions (37)

Extension	Author (truncated)	Version
Bookmarks	ale	13.3.1
tsl-problem-matcher	amo	0.6.2
chalice-icon-theme	art	1.2.22
beardedicons	Bea	1.10.0
LogFileHighlighter	emi	2.16.0
intellij-idea-keybindings	k--	1.5.9
feather-vscode	mel	1.0.1
fluent-icons	mig	0.0.18
theme-monokai-pro-vscode	mon	1.2.0
JetBrainsIcons	Mos	1.0.5
remote-ssh	ms-	0.98.0
remote-ssh-edit	ms-	0.84.0
remote-explorer	ms-	0.4.0
rose-pine	mvl	2.8.0
back-n-forth	nic	3.1.1
material-icon-theme	PKi	4.25.0
material-product-icons	PKi	1.5.0
vscode-icons	vsc	12.2.0
wvsc-serendipity	wic	0.105.0
material-theme	zhu	3.15.8
ade-source-control	Ana	0.0.36
java-project-stup	Ana	4.0.3
vscode-eslint	dba	2.4.0
svg	joc	1.5.2
symbols	mig	0.0.9
vscode-filesize	mkx	3.1.0
vscode-dotnet-runtime	ms-	1.6.0
java	red	1.16.0
intellicode-api-usage-examples	Vis	0.2.7
vscodeintellicode	Vis	1.2.30
vscode-java-debug	vsc	0.49.1
vscode-java-dependency	vsc	0.21.2
vscode-java-pack	vsc	0.25.10
vscode-java-test	vsc	0.38.2
vscode-maven	vsc	0.41.0
jar-viewer	wma	1.2.0
change-case	wma	1.0.0

(17 theme extensions excluded)

[anandbibek]

This happens only when connected to remote dev environment and we have an active SCM plugin. I have tested with Git as well as my own custom SCM plugin. But I have not found my scm plugin code being called during that refresh icon popping up

Recording.2023-04-07.103317.mp4

[anandbibek]

Recording.2023-04-07.103606.mp4

Showing the tab and progress indicator as well

[anandbibek]

I've narrowed it down to registration of quickDiffProvider. This function gets called on every keypress provideOriginalResource(uri: Uri)

As soon as I register it, this behavior starts happening. I won't assume this is a fault of my plugin, as it happens for git plugin as well.
And I feel like this was not happening maybe a few versions back..

[lszomoru]

@anandbibek, apologies for not getting back to you on this until now. Are you able to reproduce this issue with the latest Stable release of VS Code? There have been couple of known issues related to the quick diff provider that have been fixed since you have filed this issue. Thank you!

[anandbibek]

I do see this happening every now and then, but the impact seems to have reduced a bit. Sometimes feels much faster if I just reload the window. Let me re-evaluate this and get back with latest observation.

[anandbibek]

Hi @lszomoru , I just debugged my extension right now. I still see the function public async provideOriginalResource(uri: Uri): Promise<Uri | undefined> from my quick diff provider is getting called on every keypress on the editor. Same thing with Git as well. And you can clearly see the busy indicator pop up on SCM tab/badge.

I don't think this is necessary. Maybe once every file save or maybe even less..

Problem is that every time it gets called, the autocomplete, suggestions, etc. and other editor functions get invoked only after that call returns. Introducing a clear delay in the interaction with editor.

[lszomoru]

@anandbibek, I would really like to get to the bottom of this so I was wondering if you could provide more information so that I can attempt to reproduce the issue. Looking at the list of extensions that you have installed, is it safe to assume that you are using Remote-SSH in order to connect to your remote machine? Are you able to reproduce the same behaviour with all extensions disabled except Remote-SSH? Thank you!

[anandbibek]

This would not happen if I disable all plugins. It needs at least one SCM plugin to be active and QuickDiff provider to be registered.

I can reproduce this with git plugin or with my own SCM plugin I've developed. The delay and loading animation on UI is caused by repeated calls to provideOriginalResource(uri: Uri).

I've personally debugged my own plugin and came to this conclusion. Yes, I do use remote-ssh and the issue shows up prominently on remote use case. But the actual RCA seems to be that above function should not get called on every keypress. It returns a static value in most cases and calling that repeatedly serves no real purpose.

[lszomoru]

@alexr00, would you be able to take a look at this since it's related to the quick diff provider?

[alexr00]

Yes I will look.

[alexr00]

I went back and looked at version 1.70, and I can see that it did the same thing: call provideOriginalResource on ever editor change. This isn't a new problem.

[alexr00]

I've reverted the caching change as it's flawed.

[joaomoreno]

@alexr00 What's the issue you saw that made you revert it? I remember testing it.

[alexr00]

I was getting missing quick diffs from git. They could be triggered by:

• Check out a branch.
• Open a file. <At this point the quick diff base is taken, never to be changed again>For the remaining steps, do not change the file.
• Make some changes in the file. The quick diff is correct.
• Commit your changes. <At this point the git base that we want to use as the quick diff base has been changed, but quick diff doesn't take a new base>
• Quick diffs for git for this file are now incorrect depending on which line you edit.

Since this is an old issue I don't want to make a new fix so close to release. I also think that the best fix would be to give extensions API to announce when their quick diff base has changed, which should go through API review. Example:

	/**
	 * A quick diff provider provides a {@link Uri uri} to the original state of a
	 * modified resource. The editor will use this information to render ad'hoc diffs
	 * within the text.
	 */
	export interface QuickDiffProvider {

		/**
		 * Provide a {@link Uri} to the original resource of any given resource uri.
		 *
		 * @param uri The uri of the resource open in a text editor.
		 * @param token A cancellation token.
		 * @returns A thenable that resolves to uri of the matching original resource.
		 */
		provideOriginalResource?(uri: Uri, token: CancellationToken): ProviderResult<Uri>;

		/**
		 * **NEW API**
		 * Announce that the original resource has changed. This will trigger the editor to ask the provider for the original resource again.
		 * This should be implmented for performance reasons - e.g. if the provider is able to detect that the original resource has changed and fire this event,
		 * then `provideOriginalResoure` doesn't need to be called frequently and instead can be called only when there's an actual change.
		 */
		onDidChange?: Event<Uri | undefined | null | void>;
	}