Node: buffer.toString() no longer accepts null as encoding

[ibc]

• Version: v8.1.2
• Platform: Darwin ibc-macbook 16.6.0 Darwin Kernel Version 16.6.0: Fri Apr 14 16:21:16 PDT 2017; root:xnu-3789.60.24~6/RELEASE_X86_64 x86_64
• Subsystem:

According to the doc, buffer.toString([encoding[, start[, end]]]):

encoding The character encoding to decode to. Default: 'utf8'

In Node 4/5/6/7 this works:

buffer.toString(null, 0);
buffer.toString(undefined, 0);

However, in Node 8, null does not work and produces TypeError: Unknown encoding: null.

Example:

var buf = Buffer.from("hello", 'utf8');

buf.toString(null);
// => TypeError: Unknown encoding: null

Not sure why null is no longer considered "use the default value".

[vsemozhetbyt]

It is most likely caused by the https://github.com/nodejs/node/pull/11120 and listed among the semver-major changes.

[mscdex]

To be fair though, fixing this use case and the original use case (passing 0 as the first argument to toString()) detailed in the PR that made this change would be as simple as changing === undefined to == undefined.

Whether we'd want to support such a change is another question (e.g. would anyone complain about not accepting false for example?).

[ibc]

I understand the rationale given in #11120. However, shouldn't null be also valid (and not just undefined) for encoding?

[seishun]

null was never documented as a "valid" encoding, so I don't see any reason to support it. It's just more ground for confusion.

[benjamingr]

Another +1 from me for keeping the 8.x behavior. I did not review the original PR because I saw it already had lots of love - but I'm definitely in favor of the behavior change.

[addaleax]

@vsemozhetbyt One small request … can you leave off the version-specific labels if the issue is the same on master? Otherwise it seems like the issue is only occuring on v8.x. :)

[seishun]

Closing as expected behavior.

[ibc]

Why is this the expected behavior? The signature of the method is:

buffer.toString([encoding[, start[, end]]])

So encoding is an optional argument. However, where is it written that passing encoding = undefined means "use the default value"? Is there any rule out there stating that undefined is the only way to mean that while null is invalid?

[seishun]

That's how default arguments work in JavaScript in general:

> function foo(arg = 5) { console.log(arg); }
> foo()
5
> foo(undefined)
5
> foo(null)
null

However, it might be a good idea to document that explicitly.

So encoding is an optional argument.

Per the signature, it's only optional if start and end aren't specified, otherwise it would be buffer.toString([encoding][, start[, end]]) or something like that.

[ibc]

Good and clarifying code snip. Thanks.

Per the signature, it's only optional if start and end aren't specified, otherwise it would be buffer.toString([encoding][, start[, end]]) or something like that.

Completely right. Thanks, I was wrong.