fix: scope websocket upgrades to the proxy prefix

[xianjianlf2]

Fixes #414.

@fastify/http-proxy registers a single server-wide upgrade listener that dispatches every WebSocket upgrade through fastify.routing, regardless of the prefix the proxy is mounted on. When the proxy shares its server with another upgrade handler (e.g. @fastify/websocket), it consumes and answers upgrades it does not own, corrupting those unrelated WebSocket endpoints (the reporter's "existing handlers stop working").

This scopes the shared upgrade listener: when the proxy coexists with other upgrade listeners, it only handles upgrades whose path falls within a registered proxy prefix and leaves the rest untouched for the owning handler. When the proxy is the sole upgrade listener, behaviour is unchanged — every upgrade is routed exactly as before, so out-of-prefix requests are still rejected normally (existing ws-prefix-rewrite behaviour is preserved).

Added test/ws-upgrade-prefix.js, which fails on main (an out-of-prefix upgrade is answered with a 404 by the proxy) and passes with this change. Full suite green at 100% coverage.

Note for reviewers: @fastify/websocket has the mirror-image global upgrade listener, so a proxy route and a @fastify/websocket route on the same path still conflict — that needs a reciprocal change on their side. This PR fixes the http-proxy side: it no longer steals upgrades outside its own prefix.

Closes #414

[mcollina]

lgtm

[Eomm]

i would like to a test only

[Eomm]

Suggested change

	})
	})
	test('multiple proxies each own their own prefix', async (t) => {
	const upstream = await createEchoUpstream(t)
	const server = Fastify()
	server.register(proxy, { prefix: '/pub', upstream, websocket: true })
	server.register(proxy, { prefix: '/api', upstream, websocket: true })
	await server.listen({ port: 0, host: '127.0.0.1' })
	t.after(() => { server.close() })
	const port = server.server.address().port
	mountStandalone(t, server, '/standalone')
	assert.strictEqual(await connect(port, '/standalone'), 'standalone:hello')
	assert.strictEqual(await connect(port, '/pub/x'), 'proxied:hello')
	assert.strictEqual(await connect(port, '/api/x'), 'proxied:hello')
	})

[xianjianlf2]

Added this in 508cc3a, thanks. The new test covers two prefixed websocket proxies on the same Fastify server plus a standalone /standalone upgrade listener, so /pub/x and /api/x both stay proxied while the standalone path is left alone.

Validation:

• node --test test/ws-upgrade-prefix.js
• npm run lint -- test/ws-upgrade-prefix.js

[xianjianlf2]

I checked this one again. If I keep only the tests and drop the index.js change, the new websocket-prefix tests fail with Unexpected server response: 404, so main does not seem to have the behavior yet.

Do you mean you want this split as a test-only PR first, or is there another existing implementation path you want the test to cover?

[xianjianlf2]

Thanks for the review. I rechecked the branch: if I drop the change and keep only the tests, the new websocket-prefix cases fail with , so the current behavior does not cover this scenario yet.

Do you want me to split this into a test-only PR first, or is there another implementation path you had in mind for the websocket-prefix case?

[xianjianlf2]

Thanks for the review. I rechecked the branch: if I drop the index.js change and keep only the tests, the new websocket-prefix cases fail with Unexpected server response: 404, so the current main behavior does not cover this scenario yet.

Do you want me to split this into a test-only PR first, or is there another implementation path you had in mind for the websocket-prefix case?