[kmitchel]

Fixes #1569

Problem

When connecting to a WebSocket URL with an IPv6 address such as ws://[::1]:8883, url.parse() in src/lib/connect/index.ts strips the square brackets from the hostname (hostname: '::1').

Downstream in ws.ts (as well as ali.ts and wx.ts), buildUrl() reconstructed the URL using ${opts.protocol}://${opts.hostname}:${opts.port}${opts.path}, yielding ws://::1:8883/. Because RFC 3986 and WHATWG URL standards require IPv6 hostnames in URLs to be enclosed in square brackets, passing this string to new WebSocket() or new URL() immediately threw:

TypeError [ERR_INVALID_URL]: Invalid URL: ws://::1:8883/

This also affected connections using options objects with IPv6 addresses (e.g. { host: '::1', port: 8883, protocol: 'ws' }).

Solution

• Added a formatUrlHost helper function in src/lib/shared.ts that ensures unbracketed IPv6 hostnames (containing : without leading/trailing brackets) are enclosed in [...] when constructing URL strings.
• Updated buildUrl in src/lib/connect/ws.ts, src/lib/connect/ali.ts, and src/lib/connect/wx.ts to use formatUrlHost.
• Preserved raw unbracketed hostnames for socket-based connections (net.connect, tls.connect) where unbracketed IPs are expected.

Testing

• Added unit tests in test/node/mqtt.ts validating:
  1. Connecting via IPv6 WebSocket URL string (ws://[::1]:8883).
  2. Connecting via options object with IPv6 host ({ host: '::1', port: 8883, protocol: 'ws' }).
• Verified npm run build and eslint pass cleanly.