Snippet Choice Traps Focus

[brenapp]

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

• VS Code Version: 1.96.0
• OS Version: Windows 11, and Mac OS

Version: 1.96.0 (user setup)
Commit: 138f619c86f1199955d53b4166bef66ef252935c
Date: 2024-12-11T02:29:09.626Z
Electron: 32.2.6
ElectronBuildId: 10629634
Chromium: 128.0.6613.186
Node.js: 20.18.1
V8: 12.8.374.38-electron.0
OS: Windows_NT x64 10.0.22631

My extension's Language Server provides snippets to complete function documentation as part of its textDocument/completion handler. Here is an example snippet it provides:

;---------
; SCOPE:        ${1|PRIVATE,INTERNAL,PUBLIC|}
; DESCRIPTION:  ${2}
; PARAMETERS:
;   subject (${3|I,O,IO|},${4|REQ,OPT|}${5}) - ${6}
;   body (${7|I,O,IO|},${8|REQ,OPT|}${9}) - ${10}
;   inst (${11|I,O,IO|},${12|REQ,OPT|}${13}) - ${14}
;   interval (${15|I,O,IO|},${16|REQ,OPT|}${17}) - ${18}
;${0}
;---------

When the user offers the snippet, the content is inserted correctly. However, when they tab to one of the lines below PARAMETERS: and stop on any of the ${X|I,O,IO|} and ${X|REQ,OPT|} tab choices, they can no longer Shift+Tab to a tab stop before the choice. Interestingly, if the user has reached the ${2} tab stop, they can tab back to the $1 choice.

In order to verify this was not an issue with the extension itself, I copied this snippet to be a user-configured global snippet per these instructions.

{
	"Function Header": {
		"scope": "",
		"prefix": ";",
		"body": [
			";---------",
			"; SCOPE:        ${1|PRIVATE,INTERNAL,PUBLIC|}",
			"; DESCRIPTION:  ${2}",
			"; PARAMETERS:",
			";   subject (${3|I,O,IO|},${4|REQ,OPT|}${5}) - ${6}",
			";   body (${7|I,O,IO|},${8|REQ,OPT|}${9}) - ${10}",
			";   inst (${11|I,O,IO|},${12|REQ,OPT|}${13}) - ${14}",
			";   interval (${15|I,O,IO|},${16|REQ,OPT|}${17}) - ${18}",
			";${0}",
			";---------"
		]
	}
}

Steps to Reproduce:

1. Create this snippet in your global snippet configuration
2. In a new document, accept the snippet
3. Tab to the I/O/IO tab choice on the line subject parameter.
4. You can no longer shift tab back to ${2}

[jrieken]

Thanks for the detailed issue ❤

I can see that no command is executed

 INFO [KeybindingService]: | Resolving shift+[Tab]
log.js:230  INFO [KeybindingService]: \ From 5 keybinding entries, no when clauses matched the context.
log.js:230  INFO [KeybindingService]: + Ignoring single modifier shift due to it being pressed together with other keys.

Which mean this condition doesn't hold (which seems wrong/strange)

vscode/src/vs/editor/contrib/snippet/browser/snippetController2.ts

Line 340 in 929ce7c

precondition: ContextKeyExpr.and(SnippetController2.InSnippetMode, SnippetController2.HasPrevTabstop),

[jrieken]

My former comment isn't correct (apart from the praise for this issue). Actually this command is being triggered

 INFO [KeybindingService]: | Resolving shift+[Tab]
log.js:230  INFO [KeybindingService]: \ From 5 keybinding entries, matched acceptAlternativeSelectedSuggestion, when: suggestWidgetHasFocusedSuggestion && suggestWidgetVisible && textInputFocus, source: built-in.
log.js:230  INFO [KeybindingService]: + Invoking command acceptAlternativeSelectedSuggestion.
log.js:230  INFO [KeybindingService]: / Soft dispatching keyboard event