Snippets in assists don't work anymore

[jonas-schievink]

We have a custom LSP extension for snippets in assists, it doesn't seem to work anymore:

fn f() {
    $0()$0
}

Apply "Extract variable"

fn f() {
    let $0var_name = ();
    var_name
}

...but there's no snippet

[ivan770]

Is this reproducible in editors other than VS Code? Trace logs show that we send snippet insert text format

[ivan770]

Got it narrowed down to placeholderLength always being at zero, thus putting cursor at the beginning of placeholder but without selecting it

[jonas-schievink]

It seems that this was never supported like I thought it was, but I've fixed some bugs around this in #8210

[jonas-schievink]

Closing, since the known issues were fixed in #8210, even though that didn't end up using this feature