Update debugJsonValue to accept unknown

[GauBen]

Hey! We started migrating a large code base to protobuf, we'll probably be uncovering a few bugs on the way.

This merge request addresses an issue regarding debugJsonValue:

TypeError: Cannot read properties of undefined (reading 'toString')
     at Object.debugJsonValue [as debug]
     ...

[CLAassistant]

All committers have signed the CLA.

[timostamm]

If this happened during parsing of a valid JSON value, it is a bug.

Note that fromJson only parses from a JSON value (anything returned by JSON.parse). If you coerce the type system and pass undefined or an object containing undefined, you run into undefined behavior. For example:

import { Struct } from "@bufbuild/protobuf";
Struct.fromJson(undefined); 

The compiler should error with TS2345: Argument of type 'undefined' is not assignable to parameter of type 'JsonValue' on line 2. If you run this without compiling, you will see the error you mentioned.

Can you provide details on how this error occurred?

[GauBen]

It was indeed not a valid JSON, but called with undefined as first parameter: Message.fromJson(somethingThatCouldReturnUndefined()).

[timostamm]

It was indeed not a valid JSON, but called with undefined as first parameter: Message.fromJson(somethingThatCouldReturnUndefined()).

That should be caught by the TypeScript compiler:

import { Duration, JsonValue } from "@bufbuild/protobuf";
function somethingThatCouldReturnUndefined(): JsonValue | undefined {
  return undefined;
}
Duration.fromJson(somethingThatCouldReturnUndefined());
// TS2345: Argument of type 'JsonValue | undefined' is not assignable to
// parameter of type 'JsonValue'. Type 'undefined' is not assignable to type
// 'JsonValue'.

We could change the signature:

- fromJson(jsonValue: JsonValue, options?: Partial<JsonReadOptions>)
+ fromJson(jsonValue: JsonValue | undefined, options?: Partial<JsonReadOptions>)

But it would be very unusual for a function to accept undefined as an argument only to reject it by raising an error. Depending on context, maybe it could help to JSON.stringify() the return value of somethingThatCouldReturnUndefined() and use Message.fromJsonString()? This effectively passes the value through a JSON roundtrip, guaranteeing that the value is valid JSON.

[GauBen]

That should be caught by the TypeScript compiler

It wasn't because one of the branch was returning any (like JSON.parse does), making JsonValue noneffective

I'd advocate for fromJson to keep its actual signature and making debugJsonValue more resilient by accepting unknown as argument instead of JsonValue and performing additional runtime checks

[timostamm]

making debugJsonValue more resilient by accepting unknown as argument

👍 that is reasonable.

Changing the default case to return String(json) instead of json.toString should be a simple solution for everything that falls through. Would be happy to accept this improvement.

[GauBen]

Updated with this improvement!

[timostamm]

Thank you 🙂

Pushed up a commit with updated bundle size benchmark (make bench).

[GauBen]

It made the package 3 bytes smaller, which is an absolute win