A transformer that does nothing breaks `parcel serve`

[SirPepe]

🐛 bug report

I built a transformer that does nothing:

const { Transformer } = module.require("@parcel/plugin");

module.exports = new Transformer({
  async transform({ asset }) {
    return [asset];
  }
});

If I configure parcel to apply this transformer to HTML files, parcel serve returns errors, but parcel build works fine. When the transformer is removed from .parcelrc, parcel serve stops throwing errors.

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

{
  "name": "parcel-transformer-noop-repro",
  "version": "0.0.0",
  "private": true,
  "workspaces": [
    "plugins/*"
  ],
  "description": "",
  "scripts": {
    "build": "parcel build src/pages/content.html --no-cache --log-level verbose --dist-dir out",
    "dev": "parcel src/pages/content.html --no-cache --log-level verbose --dist-dir out"
  },
  "author": "[email protected]",
  "license": "MIT",
  "dependencies": {
    "parcel": "^2.9.0",
    "parcel-transformer-noop": "parcel-transformer-noop"
  }
}

{
  "extends": "@parcel/config-default",
  "transformers": {
    "*.html": [
      "parcel-transformer-noop",
      "..."
    ]
  }
}

🤔 Expected Behavior

Adding a transformer that does nothing should do nothing.

😯 Current Behavior

Adding a transformer that does nothing throws errors in parcel serve:

$ npx parcel src/pages/content.html --no-cache --log-level verbose --dist-dir out
Server running at http://localhost:1234
🚨 Build failed.

@parcel/core: Failed to resolve '7173186769850218' from './src/static/1.htm'
@parcel/resolver-default: Cannot load file './7173186769850218' in './src/static'.

parcel build works:

npx parcel build src/pages/content.html --no-cache --log-level verbose --dist-dir out
✨ Built in 714ms

out/content.html                    6.34 KB    255ms
out/up_/static/1.html                   0 B    223ms
out/up_/static/navi.jpg            10.85 KB    194ms
out/navi.thumbnail.4d7c1d7f.jpg     1.69 KB    162ms
out/up_/static/2.html                   0 B    255ms
out/up_/static/3.html                   0 B    223ms

🔦 Context

I am attempting to build a new static site from some ancient html sources, nothing special.

💻 Code Sample

Minimal reproduction: https://github.com/SirPepe/parcel-transformer-noop-repro

🌍 Your Environment

Software	Version(s)
Parcel	2.10.3
Node	18.16.0
npm/Yarn	9.5.1
Operating System	Ubuntu 22.04.3 LTS

[mischnic]

It only seems to happen when using .htm as opposed to .html. So renaming everything to .html might be a workaround for you

[SirPepe]

So renaming everything to .html might be a workaround for you

That kind of works, but the point of my setup is to keep the existing ancient files as they are. A better workaround might be to also add the transformer for the .htm extension:

{
  "extends": "@parcel/config-default",
  "transformers": {
    "*.html": [
      "parcel-transformer-noop",
      "..."
    ],
    "*.htm": [
      "parcel-transformer-noop",
      "..."
    ]
  }
}