@mcollina @ronag @nodejs/streams

const { Duplex } = require('stream');

const d = new Duplex({
  writable: false,
  write(chunk, encoding, cb) {
    console.log(chunk.toString());
    cb();
  }
});

console.log(d.writable);   // false! as expected...

d.write('darn it');  // prints, 'darn it' and returns true

This isn't a bug since it's been like this forever but the behavior is really counter intuitive, especially since after calling d.end() and then doing a d.write() we get a proper write after end error. It makes implementing a custom Duplex (e.g. QuicStream) more difficult because of the additional checks that need to be made to ensure that even tho the Duplex isn't writable no-one is writing to it.

Not sure what the fix is immediately but wanted to discuss it first.

The ideal behavior, I would think, is an error similar to write after end if write() is called on a non-writable Duplex.