Provide support for comma insertion with snippet completion

Bug Report

Support comma insertion with snippet completion

🔎 Search Terms

object literal method snippet

💻 Code

interface T {
    aaa: string;
    foo(): void;
}

const obj: T = {
    aaa: ""
    /**/
}

🙁 Actual behavior

const obj: T = {
    aaa: ""
    foo() {
        
    },
}

On selecting the completion that inserts just foo, the comma gets inserted, but on selecting the snippet completion foo(), the comma is not inserted. This happens because both the comma insertion and snippet completion have their own CompletionSource.

🙂 Expected behavior

const obj: T = {
    aaa: "",
    foo() {
        
    },
}