Experiment: Stack traces with TypeScript

stack-traces.ts

// `CallSite` is the class representing a stack frame in the V8 spec 
// (see https://v8.dev/docs/stack-trace-api#customizing-stack-traces)

// hat tip to the callsites package, where I'm importing the `CallSite` type from: https://github.com/sindresorhus/callsites
import { CallSite } from "https://raw.githubusercontent.com/sindresorhus/callsites/7fb22a67645ea741cc016937e8f3662eb533eb6e/index.d.ts";

// there is a default implementation for preparing stack traces on the Error object, but TypeScript doesn't recognise
// this. (maybe because it's not present in all runtimes? or maybe the default is initialised in some other way?)
type ErrorWithPrepFn = ErrorConstructor & { prepareStackTrace?: (error: Error, stack: CallSite[]) => unknown}

// definitions
function inner() {
    console.log("Stack from inside `inner()`:")
    console.log(new Error("").stack)
}

function outer() {
    inner()
}

function outermost() {
    outer()
}

function outsideEntirely() {
  console.log("I'm running now, so `outsideEntirely` won't appear in the stack trace.")
}

function run() {
  outsideEntirely();
  outermost();
}

// define a handler to assign to `Error.prepareStackTrace`
function returnFunctionNames(_: Error, stack: CallSite[]) {
    return stack.map(call => call.getFunctionName());
}

// here we assign our custom handler; when an error is thrown,
// this method will be called with the error and the call stack at the time
// the error arose
(Error as ErrorWithPrepFn).prepareStackTrace = returnFunctionNames


/**
  * run code
  * expected output:
    > I'm running now, so I won't appear in the stack trace.
    > Stack from inside `inner()`:
    > [ "inner", "outer", "outermost", "run", null ]
*/
run()

I wrote this to run in Deno.