Not using "main" and other common package.json fields by default

💬 RFC

The main / module / browser fields in package.json should be ignored by default.

Using them could be behind a cli flag, or require the “targets” field in package.json.

🔦 Context

Common setup:

npm init -y
npm i parcel@next
npm i <project packages>
# write basic entrypoint files, including possibly index.js in root
npx parcel watch ./src/entryfile.js --dist-dir ./dist --no-autoinstall

Running this I would expect to build entryfile.js and output it in /dist, but since npm init adds a "main" field, Parcel surprisingly ignores --dist-dir.

Having this surprising functionality makes it more difficult to guide new users through setup, and requires inspecting package.json to ensure it doesn’t have a common (ignored) field just for regular operation.

[samsch]

Recent issues which wouldn’t happen with this change: https://github.com/parcel-bundler/parcel/issues/6046 https://github.com/parcel-bundler/parcel/issues/6013 https://github.com/parcel-bundler/parcel/issues/5996

Also helps avoid the case fixed here: https://github.com/parcel-bundler/parcel/pull/5941

[devongovett]

I don’t believe we plan on changing this. “main”/“module”/“browser”/“types” are meant for building libraries, which will be consumed by other tools (e.g. node or another bundler) later. It would be expected that if you built the library with Parcel you’d want other tools to consume the output from Parcel rather than the original source code (which might be written in another language like TypeScript). The “source” field can be used to configure source code.

We’ve improved the diagnostics around this so that the error messages are more helpful, and prevent you from doing dangerous things. For example, the above fields only allow certain file extensions, and we prevent you from overwriting your source code as of #5941. Hopefully this is enough to prevent confusion.