Hot reload not reloading for aliased imports

[zachbryant]

🐛 bug report

I'm attempting to run the parcel dev server using a resolver I wrote for typescript tsconfig paths. However, the watcher does not detect changes in files resolved through an alias. You can see my repo here.

Update: updating my resolver to use absolute paths (in place of relative to the src root) fixes the watcher (albeit with significant performance drop), but the reload part of hot-reloading continues to be an issue.

🎛 Configuration (.babelrc, package.json, cli command)

Running parcel src/index.html to start. No babel configuration.

{
  "extends": "@parcel/config-default",
  "transformers": {
    "*.{ts,tsx}": ["@parcel/transformer-typescript-tsc"]
  },
  "validators": {
    "*.{ts,tsx}": ["@parcel/validator-typescript"]
  },
  "resolvers": ["...", "parcel-resolver-tspaths"],
  "reporters": ["...", "@parcel/reporter-bundle-analyzer"]
}

🤔 Expected Behavior

Parcel should hot-reload when changes are made in a file referenced through a resolved alias.

😯 Current Behavior

Changes are not detected not reloaded in files referenced through a resolved alias. No error.

💁 Possible Solution

I believe HMR should function the same as a build when it comes to resolving files.

🔦 Context

The context is that my index.ts imports from @components/App, which is aliased in my tsconfig.js. This builds fine, and I don't want to move my paths to package.json

💻 Code Sample

My repo: https://github.com/zachbryant/react-starter

Specifically, look in src/index.tsx and arc/components/App.tsx.

🌍 Your Environment

Software	Version(s)
Parcel	2.0.0-beta.3.1
Node	v14.16.0
npm/Yarn	yarn 1.22.5
Operating System	Ubuntu 20.04 64bit

[zachbryant]

Updated environment from beta 2 to 3.1 since this has persisted

[vdtrung]

Maybe you're using WSL2, I don't know but I have the same issue then I change back to use WSL1, and it's worked.

To see what WSL version are you on (open PowerShell by admin):
wsl --list --verbose - if you're in version 2 then try to go back version 1 by wsl --set-version <distribution name> 1

[zachbryant]

Maybe you're using WSL2, I don't know but I have the same issue then I change back to use WSL1, and it's worked.

To see what WSL version are you on (open PowerShell by admin):
wsl --list --verbose - if you're in version 2 then try to go back version 1 by wsl --set-version <distribution name> 1

I'm using Ubuntu, but perhaps something changed in your Linux subsystem configuration when you made the switch. In any case I don't have this issue with other bundlers, so I think it's a parcel related issue.

[devongovett]

Two problems I see:

1. You should probably have your custom resolver run before the default rather than after. Resolvers short circuit - the first plugin that returns a result wins.

2. I didn't run your code but just glancing at your plugin make sure it returns an absolute path, not a relative one. Otherwise watching won't work.

[zachbryant]

Two problems I see:

1. You should probably have your custom resolver run before the default rather than after. Resolvers short circuit - the first plugin that returns a result wins.

2. I didn't run your code but just glancing at your plugin make sure it returns an absolute path, not a relative one. Otherwise watching won't work.

Thanks for the suggestions Devon, I'll check these out and report back

[zachbryant]

@devongovett, I tried your suggestions and point 2 was part of the issue. I really appreciate you sharing it! Although I don't understand why parcel needs a full path vs relative to the project root. AFAICT, this nuance needs documented.

Now that it's working, a few things stick out to me:

• The behavior is similar to hot reload or hot module replacement not working with electron #6229: it builds files resolved by my plugin, but does not reload when they change. When I edit unaliased files like index.tsx all changes appear in browser as expected.
• Using absolute paths, cold build time (cached or not) spikes by 21x and rebuilds by 3x. I checked if it's resolving the paths that causes this, but it must be something internal to parcel. With relative paths I get 1.5s build/~500ms reload time, compared to 21s build/1.5s reload time. I wonder if optimization using relative paths is possible here?

For point 1, I was aware that it short circuits, but in the past this caused some errors. Seems it's been fixed in beta 3.1 :)

[zachbryant]

Seems like this was fixed in the v2 release. Closing now.