node:repl docs code not working (Starting multiple REPL instances against a single running instance) #3861
Description
Details
node:repl docs
Under Starting multiple REPL instances against a single running instance there is a code that demonstrates the sharing of a single global object among multiple repl instances. However, the code in question does not work. That is, when I run this code and connect to it with telnet localhost 5001, the variable that I define in the telnet instance does not get reflected in the normal stdin/out instance.
I found that this is most likely because useGlobal option is set to false by default in repl.start, as explained in the same document. To enable this, I needed to explicitly set this to true in repl.start argument like this. Now the code works as expected.
const net = require('node:net');
const repl = require('node:repl');
let connections = 0;
repl.start({
prompt: 'Node.js via stdin> ',
input: process.stdin,
output: process.stdout,
useGlobal: true //modified
});
net.createServer((socket) => {
connections += 1;
repl.start({
prompt: 'Node.js via Unix socket> ',
input: socket,
output: socket,
useGlobal: true //modified
}).on('exit', () => {
socket.end();
});
}).listen('/tmp/node-repl-sock');
net.createServer((socket) => {
connections += 1;
repl.start({
prompt: 'Node.js via TCP socket> ',
input: socket,
output: socket,
useGlobal: true //modified
}).on('exit', () => {
socket.end();
});
}).listen(5001);Also, there is a second but minor problem in this code. After I exit from this program and try to execute this again, the following error is thrown.
Node.js via stdin> node:events:371
throw er; // Unhandled 'error' event
^
Error: listen EADDRINUSE: address already in use /tmp/node-repl-sock
at Server.setupListenHandle [as _listen2] (node:net:1302:21)
at listenInCluster (node:net:1367:12)
at Server.listen (node:net:1465:5)
at Object.<anonymous> (/Users/yoshi/prog/repl/telnet2.js:22:4)
at Module._compile (node:internal/modules/cjs/loader:1101:14)
at Object.Module._extensions..js (node:internal/modules/cjs/loader:1153:10)
at Module.load (node:internal/modules/cjs/loader:981:32)
at Function.Module._load (node:internal/modules/cjs/loader:822:12)
at Function.executeUserEntryPoint [as runMain] (node:internal/modules/run_main:79:12)
at node:internal/main/run_main_module:17:47
Emitted 'error' event on Server instance at:
at emitErrorNT (node:net:1346:8)
at processTicksAndRejections (node:internal/process/task_queues:83:21) {
code: 'EADDRINUSE',
errno: -48,
syscall: 'listen',
address: '/tmp/node-repl-sock',
port: -1
}
To get this to work again, I had to remove /tmp/node-repl-sock file from my laptop. I don't have a good idea on how Unix socket works, but I think there should be an additional cleanup process in the code.
Node.js version
v16.8.0
Example code
No response
Operating system
macOS Mojave 10.14.6
Scope
docs node:repl docs
Module and version
Not applicable.