Error.prepareStackTrace is exposed to user code

[ghost]

Title should describe this well enough.

Input:

console.log("prepareStackTrace" in Error);

Expected output:

false

Actual output:

true

I don't think any browsers do this.

Exposed here:

deno/runtime/js/99_main.js

Lines 158 to 167 in f3ead9c

	// only for compiled standalone binaries.
	let prepareStackTrace;
	if (runtimeOptions.applySourceMaps) {
	prepareStackTrace = core.createPrepareStackTrace(
	errorStack.opApplySourceMap,
	);
	} else {
	prepareStackTrace = core.createPrepareStackTrace();
	}
	Error.prepareStackTrace = prepareStackTrace;

[nayeemrmn]

This is intentional, Error.prepareStackTrace() is a V8 concept supported in Chrome, but it doesn't have a default value. It does for us because we use it for internal purposes. There's a TODO to expose it properly for users in the way Chrome does:

deno/cli/dts/lib.deno.shared_globals.d.ts

Lines 884 to 885 in f3ead9c

	// TODO(nayeemrmn): Support `Error.prepareStackTrace()`. We currently use this
	// internally in a way that makes it unavailable for users.

[ghost]

This is intentional, Error.prepareStackTrace() is a V8 concept...

Exactly, it's a nonstandard V8 "feature."
Imho, to use it at all breaks web compatibility to a certain degree.

[nayeemrmn]

This is discussed in #5254 about Error.captureStackTrace. The gist of it is that Deno is tightly coupled to V8, and if V8 exposes something like this with documentation that suggests it's for user code (not host environments) to take advantage of, we would just pass it on. It's not clear how feasible it is to hide it, and we're only making the web compatibility trade-offs which any V8-based web browser is.

[ghost]

Oh, there was a PR explicitly exposing it, didn't find that.

In that case, is there a plan to allow users to take advantage of it?
Where is it used internally?

Could I try setting up a hacky workaround in the meanwhile?

[nayeemrmn]

(Its friend Error.captureStackTrace was explicitly exposed, Error.prepareStackTrace is the one that's used internally for now.) In the future I think we can replace our internal use of Error.prepareStackTrace = ourCallback with Isolate::set_prepare_stack_trace_callback(our_callback) in Rust. This is mentioned as point 2 in #7644.

[ghost]

Closing, as this is known and intentional.