insertSnippet can put snippet selections in wrong positions

[MrAndersen1]

Does this issue occur when all extensions are disabled?: Yes

• VS Code Version: 1.66.0-insider (Universal) Commit: db0525f
• OS Version: macOS Big Sur 11.6

Steps to Reproduce:
I created a new extension to test this where I basically use a keybinding to trigger a command inserting a snippet.

Speed is of the essence in a lightweight environment/extension in order to reproduce this so that's why we need the keybinding.

"contributes": {
	"commands": [
		{
			"command": "testextension.helloWorld",
			"title": "Hello World"
		}
	],
	"keybindings":[
		{
			"command": "testextension.helloWorld",
			"key": "ctrl+m"
		}
	]
}

vscode.commands.registerCommand('testextension.helloWorld', async () => {
	const line = vscode.window.activeTextEditor?.document.lineAt(vscode.window.activeTextEditor?.selection.start);
	const snippet = new vscode.SnippetString("aProperty: aClass<${2:boolean}> = new aClass<${2:boolean}>();\n");
	// I believe, but am not sure, that it's important that the place to insert the snippet on differs from the cursor position.
	await vscode.window.activeTextEditor?.insertSnippet(snippet, new vscode.Position(line?.lineNumber! + 5, 4));	
});

in a new file containing

{
    text
    more text
    some more text
    even more text
    and some more
    additional
    text
}

putting the cursor after the first "text", pressing enter twice quickly followed by crtl+m puts the snippet cursors on "ean> = " and "ean>();" instead of "boolean" and "boolean"

[jrieken]

I can reproduce but don't know yet what's happening...

[jrieken]

This happens because there is an indent only line. Somehow, it is being cleared when/while the snippet edit is being made. That invalidates the offset we have cached at the start of the snippet session. The four whitespace characters that are being removed are exactly those four character by which the placeholders are shifting.

From the recording you can see that this only happens when the indentation is cleaned-up (line 4) while the snippet is being inserted.

Screen.Recording.2022-03-25.at.17.12.27.mov

[jrieken]

/cc @alexdima let's discuss Monday. It seems that I am suffering from some auto-clean on edit behaviour here

[MrAndersen1]

Nice, will test it when I get my hands on it.

[MrAndersen1]

It works fine on my end now @jrieken 👍

[MrAndersen1]

/verified