AOT: sock.write() via Map-retrieved object silently drops ~100-byte packets inside 'data' callback (closure sock.write works) #91

Environment

• perry 0.5.98
• macOS arm64 (darwin 25.4.0)

Problem

Inside a net.Socket 'data' event callback, calling obj.sock.write(bytes) where obj was retrieved from a Map.get() lookup silently fails to deliver the bytes to the peer, even though:

• sock.write(bytes) returns immediately (with undefined — no error)
• The same bytes buffer, written via the closure-captured sock reference, reaches the server and gets a response
• Small writes (≤5 bytes) via the Map path DO work; the failure appears only for larger writes (the driver hits it at 101 bytes)

This looks like the same class of bug as #87 (Promise resolve via property dispatch) but for Socket.write — the method call returns but the underlying I/O op never happens.

Minimal repro

// repro.ts — requires a TCP service that speaks first (any MySQL server).
import * as net from 'node:net';
import { writeHandshakeResponse41 } from '@perry/mysql/src/protocol/writer';
import { writePacket } from '@perry/mysql/src/protocol/framing';
import { DEFAULT_CLIENT_CAPABILITIES, CLIENT_CONNECT_ATTRS } from '@perry/mysql/src/protocol/capabilities';
import { sha256Scramble } from '@perry/mysql/src/auth/caching-sha2';

const STATES = new Map<number, { sock: net.Socket }>();
const sock = net.createConnection('YOUR.MYSQL.HOST' as never, 3306 as never);
STATES.set(1, { sock: sock });

let count = 0;
sock.on('data', (chunk: Buffer) => {
    count += 1;
    if (count === 1) {
        // Extract 20-byte challenge from HandshakeV10 at known offsets, scramble, build packet...
        // (elided for brevity — full repro in @perry/mysql tests/perry-aot-smoke.ts)
        const bytes = /* 101-byte HandshakeResponse41 */;
        const st = STATES.get(1);
        if (st !== undefined) {
            st.sock.write(bytes);   // ← via Map-retrieved socket
        }
        console.log('[write] done');
    } else {
        console.log('[data #2] server responded!');
        process.exit(0);
    }
});
setTimeout(() => { console.log('timeout'); process.exit(1); }, 6000);

Change the key line to:

sock.write(bytes);   // ← closure-captured socket, same bytes

and the program immediately receives the server's response.

Observed (Map path)

[data #1] len=95        — got HandshakeV10
[write] bytes.len=101
[write] done
timeout                  — server never sends AuthMoreData / OK / ERR

Expected (matches closure path and Node/Bun behaviour)

[data #1] len=95
[write] bytes.len=101
[write] done
[data #2] len=6         — server's AuthMoreData{0x03} FAST_AUTH_SUCCESS

Content verification

I verified the 101 bytes produced via the Map path are byte-identical to the bytes the closure path produces (both computed via writeHandshakeResponse41(...) + writePacket(1, payload)), and the MySQL server accepts the closure-sent version. So the bytes are valid; they're simply not being flushed when dispatched via obj.sock.write(...).

Hit in real code

@perry/mysql stores the net.Socket inside a ConnState struct keyed in CONN_STATES: Map<number, ConnState>. Every sendAuthFrame / sendCommand call does st.sock.write(bytes). Under Bun/Node this works perfectly (all 138 unit + 13 real-server integration tests pass). Under Perry 0.5.98 AOT, after #78–#88 were fixed, the driver successfully:

1. Connects to MySQL 8.0.45 on webserver.skelpo.net
2. Decodes HandshakeV10, receives 20-byte challenge
3. Computes correct caching_sha2_password auth response (hex matches Node's output byte-for-byte)
4. Builds valid 97-byte HandshakeResponse41 + 4-byte header = 101 bytes
5. Calls st.sock.write(bytes) — call returns normally
6. Server never responds → connect times out after 10 s

Workarounds on the @perry/mysql side are ugly (either flatten the state map out of the write path or pass the socket directly through every helper). I'd rather wait for a proper codegen fix.

Related

• AOT: Promise resolve() called via object-property/method access doesn't wake await site from socket 'data' callback #87 (resolve via property access) — same class of bug, also manifested inside 'data' callbacks.
• AOT: crypto.createHash('sha256').update(buf).digest() returns Buffer with undefined length for FIRST call inside socket-callback context #88 (crypto digest length under async context) — also called from the same pipeline.