socket.end() is not firing event 'close' in mitm after node 12.16

[timotheeg]

Ending the socket in mitm 1.7.0 is no longer emitting a close event with node 12.16 (works up to 12.15)

Repro script:

const net = require('net');

mitm = require('mitm')();
mitm.on("connection", (socket) => {
    console.log('connection')
    setTimeout(() => {
        console.log('ending');
        socket.end();
    }, 100);
});

socket = net.connect(22, 'example.org')
socket.on('connect', () => console.log('connected'));
socket.on('end',     () => console.log('end'));
socket.on('close',   () => console.log('close'));

// dummy timer to keep process alive
setTimeout(() => console.log('done'), 500);

Outputs:

<=12.15	>=12.16
``` connection connected ending end close done ```	``` connection connected ending end done ```

Expected: close event should still fire in node >=12.16.

[moll]

Hey! Thank you for the heads up. I'll take a look!

[alexjeffburke]

I think we also hit this in the unexpected-mitm module that uses mitm internally - at some point I was looking at the changes in the version of 12 that broke it and my hunt led me to this commit (if I take a version before it all worked): https://github.com/nodejs/node/commit/ed21d32a7c37d030ce4668415832a89dc8ead34c

I had hoped to use this to try to build a patch and ran out of time, but maybe that helps as a start.

[moll]

Hey, everyone! I found the close event started failing in v12.16.3 and my current guess is it was actually related to a change in WritableStream.prototype.end, rather than in the networking code. It's more likely to have been a latent bug in Mitm.js's code related to closing the socket. As I was and still am a little unclear on what the relationship between shutdown and close methods of the internal sockets is, I delegated both to closing the writable stream. Turned out calling WritableStream.prototype.end if a stream had already ended didn't call the given callback, and that caused InternalSocket.prototype.close to in turn not call back consistently. I ensured the callback gets fired every time and that seems to have fixed the problem.

I should really at some point have separate tests for all events the user-facing socket must emit, like you, @timotheeg, tested above manually with console.log.

The change itself is in https://github.com/moll/node-mitm/commit/f41a62f16dd53e473b8d36a5240edc46bb02e464#diff-300e7ee3fb2b1bc3beb9294b11d66477 and got released under Mitm.js v1.7.1 a minute ago.

Thanks again!

[timotheeg]

Many thanks @moll !