options.defaultEncoding not validated in stream.Writable constructor

[Alexthemediocre]

Version

v19.4.0

Platform

Microsoft Windows NT 10.0.22000.0 x64

Subsystem

node:stream

What steps will reproduce the bug?

Create a new stream.Writeable and supply an invalid encoding for defaultEncoding. It will accept the encoding just fine, which can lead to some strange side effects.

For a very quick test, just to show that it does not validate it:

new (require('node:stream').Writable)({defaultEncoding: 'some invalid encoding'});

For a more complete test that shows more of its effects:

const stream = require('node:stream');

console.log('stream 1');
const s1 = new stream.Writable({
   defaultEncoding: 'my invalid encoding',
   write(chunk, enc, cb) {
      console.log('dat', chunk);
      console.log('enc', enc);
      cb();
   }
});
// output:
//TypeError: Unknown encoding: my invalid encoding
//...
try {
   s1.write('test data');
} catch (err) {
   console.error(err);
}

/* ============================== */

console.log('\nstream 2');
const s2 = new stream.Writable({
   defaultEncoding: 'my invalid encoding',
   decodeStrings: false,
   write(chunk, enc, cb) {
      console.log('dat', chunk);
      console.log('enc', enc);
      cb();
   }
});
// output:
//dat test data
//enc my invalid encoding
s2.write('test data');

/* ============================== */

console.log('\nstream 3');
const s3 = new stream.Writable({
   defaultEncoding: {an: 'object'},
   write(chunk, enc, cb) {
      console.log('dat', chunk);
      console.log('enc', enc);
      cb();
   }
});
// output:
//dat <Buffer 74 65 73 74 20 64 61 74 61>
//enc buffer
s3.write('test data');

/* ============================== */

console.log('\nstream 4');
const s4 = new stream.Transform({
   defaultEncoding: 'my invalid encoding',
   transform(chunk, enc, cb) {
      console.log('dat', chunk);
      console.log('enc', enc);
      cb(chunk);
   }
});
// output:
//TypeError: Unknown encoding: my invalid encoding
//...
try {
   s4.write('test data');
} catch (err) {
   console.error(err);
}

/* ============================== */

console.log('\nnode:crypto test');
console.log('crypto.createCipheriv');

const crypto = require('node:crypto');
const encrypt = crypto.createCipheriv('aes-128-gcm', crypto.randomBytes(16), crypto.randomBytes(16), {defaultEncoding: 'an invalid encoding'});

encrypt.on('data', (chunk) => {
   console.log('data received', chunk);
});
encrypt.write('some more data');
encrypt.end();

How often does it reproduce? Is there a required condition?

As far as I can tell, it always reproduces.

What is the expected behavior?

I would expect the stream.Writeable constructor to validate the defaultEncoding option and throw an error if it is invalid.

It still can throw an error with a call to writeable.write if objectMode is false, decodeStrings is true, the chunk is a string, and no encoding is specified in the write call. Weirdly enough, it doesn't throw an error if the defaultEncoding is something other than a string, like a number or object, and converts the string provided in the write call to a buffer anyway.

const stream = require('node:stream');
// would expect an error
new stream.Writable({defaultEncoding: 'some invalid encoding'});

// would very much expect an error
new stream.Writable({defaultEncoding: 42}).write('a string');

const s = new stream.Writeable();
// throws an error, which is exactly what I would expect
s.setDefaultEncoding('some invalid encoding');

// also throws an error (expected)
s.write('a string', 42);

What do you see instead?

It does not validate invalid default encodings in the constructor, and only throws an error if the invalid default encoding is used (such as if a string is provided in a write call with no other encoding specified).

Additional information

Trying a similar thing with stream.Readable throws an error instead.

// throws an error (which is expected)
new (require('node:stream').Readable)({encoding: 'some invalid encoding'});

[marco-ippolito]

I'll open a PR to validate encodings

[marco-ippolito]

There is this comment in writable streams (but its also in readable).

node/lib/internal/streams/writable.js

Lines 121 to 126 in 762a3a8

	// Crypto is kind of old and crusty. Historically, its default string
	// encoding is 'binary' so we have to make this configurable.
	// Everything else in the universe uses 'utf8', though.
	this.defaultEncoding = (options && options.defaultEncoding) || 'utf8';

@mcollina @ronag can give more context on why defaultEncoding is not validated and whether to add some validation.
On the other end readable encoding will throw because of StringDecoder:

node/lib/internal/streams/readable.js

Lines 177 to 184 in 762a3a8

	this.decoder = null;
	this.encoding = null;
	if (options && options.encoding) {
	this.decoder = new StringDecoder(options.encoding);
	this.encoding = options.encoding;
	}
	}

[ronag]

I don't think there is any specific reason why it's not validated. PR welcome.