#14741 rspack: --port with a host prefix yields RSPACK_DEVSERVER_PORT=NaN and kills the client compilation

Summary

meteor run --port <host>:<port> makes the rspack integration compute RSPACK_DEVSERVER_PORT=NaN, and the client compilation dies before its first build with ERR_SOCKET_BAD_PORT.

--port is documented as accepting [host:]port, so this affects every app that binds an explicit host — a very common setup for tunnelled/remote development and for running several apps side by side.

Cause

calculateDevServerPort() assumes the value returned by getMeteorAppPort() is digits only:

https://github.com/meteor/meteor/blob/release/METEOR%403.5.2/packages/rspack/lib/processes.js#L135-L143

export function calculateDevServerPort() {
  const port = getMeteorAppPort();
  const basePort = 8077;

  // Sum the digits of the port
  const digitSum = port.split('').reduce((sum, digit) => sum + parseInt(digit, 10), 0);

  return basePort + digitSum;
}

but getMeteorAppPort() returns the raw --port option, host prefix included:

https://github.com/meteor/meteor/blob/release/METEOR%403.5.2/packages/tools-core/lib/meteor.js#L43-L45

export function getMeteorAppPort() {
  return Package?.meteor?.global?.currentCommand?.options?.['port'] || process.env.PORT || '3000';
}

With --port localhost:3060, parseInt('l', 10) is NaN, the sum is NaN, and 8077 + NaN is NaN. That value is then stringified into the environment of the spawned rspack process, so devServer.port ends up NaN.

Reproduction

Any rspack-enabled app on [email protected] with [email protected] / @meteorjs/[email protected]:

meteor run --port localhost:3060

=> Started MongoDB.
[rspack-cli] RangeError [ERR_SOCKET_BAD_PORT]: options.port should be >= 0 and < 65536. Received type number (NaN).
    at Server.listen (node:net:2159:5)
    at READ_WRITE (…/node_modules/webpack-dev-server/lib/Server.js:3460:23)
    at RspackDevServer.start (…/node_modules/webpack-dev-server/lib/Server.js:3458:7)
  code: 'ERR_SOCKET_BAD_PORT'

Rspack plugin error: Rspack client process exited unexpectedly (code 2) before completing its first compilation.

meteor run --port 3060 (no host) works. [::]:3005, used by meteor test setups, fails the same way.

Expected

The dev-server port should be derived from the port component only, e.g. parse the [host:]port form before summing digits, or reuse whatever the tool already uses to split --port into host and port.

Workaround

Set RSPACK_DEVSERVER_PORT explicitly:

RSPACK_DEVSERVER_PORT=8060 meteor run --port localhost:3060

Side note

The digit-sum heuristic also collides readily even when it does work — 3010, 3100, 3001 and 1300 all map to 8081 — so apps started on different ports can still fight over one dev-server port.

Versions

Meteor [email protected]
[email protected] (Atmosphere), @meteorjs/[email protected], @rspack/core / @rspack/cli 1.7.11
macOS 26.6.2 (arm64), Node 24 (bundled with the Meteor tool)