Dynamic snippet evaluation in VSCode

Question

Is it possible for a snippet to insert a dynamically computed completion or snippet in Visual Studio Code?

I would like a snippet for inserting date and time strings of various formats. For example if you type date, the current date in ISO format would automatically be expanded.

There is a facility in Sublime Text to do this in the python API via the on_query_completions method in the EventListener class. There the implementation would be very simple:

def on_query_completions(self, view, prefix, locations):
  if prefix == 'date':
    val = datetime.now().strftime('%Y-%m-%d')
  return [(prefix, prefix, val)] if val else []

I have read the documentation on User Defined Snippets, but it appears that one can only insert pre-defined text with tab-stops and variables that the user fills in.

If this isn't possible with the functionality exposed by the snippet API, would I be able to implement something similar with via a lower-level plugin/extension API?

I do realize that there is an existing extension called Insert Date and Time but this works via the command pallet instead of a dynamic expansion.

Answer 1

Although, it's possible to achieve simple date-time stuff without extensions:

"⌚ Date Time SNIPPET": {
    "prefix": "datetime",
    "body": [
        "${CURRENT_YEAR}-${CURRENT_MONTH}-${CURRENT_DATE}T${CURRENT_HOUR}:${CURRENT_MINUTE}:${CURRENT_SECOND}",
    ]
}

The question is about dynamic snippets. And here's an example of using CompletionItemProvider:

const datetimeProvider = vscode.languages.registerCompletionItemProvider(
    {
        scheme: 'file',
        // language: 'typescript',
    },
    {
        provideCompletionItems(document: vscode.TextDocument, position: vscode.Position) {
            const completionItem = new vscode.CompletionItem('datetime ⌚', vscode.CompletionItemKind.Snippet);
            completionItem.insertText = new Date(Date.now() - new Date().getTimezoneOffset() * 60000).toISOString().split('.')[0];
            return [completionItem];
        }
    },
    // ''// trigger character
);