Fix HMR server when WebSocket proxy is running on the same port

[bminer]

↪️ Pull Request

HMR server's WebSocket always upgrades the HTTP server to a WebSocket regardless of the request URL. This patch ensures that the path must start with the HMR_ENDPOINT before doing so.

Fixes #6994

💻 Examples

None

🚨 Test instructions

Please see issue #6994. Also, this PR needs to be tested before it is merged.

✔️ PR Todo

• Added/updated unit tests for this change
• Filled out test instructions (In case there aren't any unit tests)
• Included links to related issues/PRs

[mischnic]

Also, this PR needs to be tested before it is merged

Why the strong emphasis 😄 ? Any particular cases where you're not sure whether they work?

Would it be feasible to add an integration test (that your own WS connections can be proxied)?

parcel/packages/core/integration-tests/test/proxy.js

Line 50 in 7a0bf13

describe('proxy', function () {

[mischnic]

In case you didn't notice, 27 existing tests are also failing. e.g.

  1) hmr
       hmr server
         should emit an HMR update for the file that changed:
     Error: Timeout of 50000ms exceeded. For async tests and hooks, ensure "done()" is called; if returning a Promise, ensure it resolves. (/home/runner/work/parcel/parcel/packages/core/integration-tests/test/hmr.js)
      at listOnTimeout (node:internal/timers:569:17)
      at processTimers (node:internal/timers:512:7)

  2) hmr
       hmr server
         should emit an HMR update for all new dependencies along with the changed file:
     Error: Timeout of 50000ms exceeded. For async tests and hooks, ensure "done()" is called; if returning a Promise, ensure it resolves. (/home/runner/work/parcel/parcel/packages/core/integration-tests/test/hmr.js)
      at listOnTimeout (node:internal/timers:569:17)
      at processTimers (node:internal/timers:512:7)

[bminer]

@mischnic - I added the strong emphasis because I committed without testing, and as a programmer, I'm sure you know that nothing ever works the first time. Haha!

Anyway, could you give me the 30-second crash course into running the test suite? I should have some time this week to get this PR working.

[mischnic]

esbuild and Flow also fail, so you need these commands to see all the CI failures locally:

yarn lint
yarn flow
yarn test:integration # run all tests
yarn test:integration test/hmr.js # to run just packages/core/integration-tests/test/hmr.js

And in case you haven't done that already, before the above, run this to install deps and compile the Rust parts

yarn && yarn build-native

[bminer]

Okay, code is at least working now. Linters and relevant tests passing.

The primary issue here was that I forgot to modify the HMR runtime to connect to HMR_ENDPOINT instead of / to allow the HMRServer to distinguish these requests from other requests to be proxied.

Only thing left to do is actually write a test that proves #6994 is now solved.

[bminer]

Should be now ready to merge. Thanks for guiding me on how to run the tests. Made development a lot easier.

[bminer]

Any thoughts on when this can get merged?

[GeorchW]

Is this something that has to wait until (or is incompatible with) Parcel v3?

[bminer]

@GeorchW - there is no reason to wait for Parcel v3. This is a simple bug fix as far as I'm concerned.

[bminer]

Any reason why this has not been fixed yet?

[bminer]

This is still a bug with a PR that provides a fix, complete with regression tests.

Is there a reason why it has not been merged? What can I do to help?

[sebbdk]

It's 2026 now :)

If the tests pass, could this be merged?