[Feature Request]: prebundle rspack config file by rspack itself for better config extensions support

[fi3ework]

What problem does this feature solve?

Support multiple config file extensions, such as mjs ts cjs mts cts, especially ts for better intellisense and type check.

What does the proposed API of configuration look like?

Utilize rspack itself to pre-bundle the config file. The bundling should have the following features:

1. A default unmodifiable sane nodejs lib config
2. Externalize dependencies in node_modules
3. Support both ESM and CJS output
4. Hijacking require.extensions to load CJS and use temp file (before --loader landed) for ESM.

[wernerbihl]

I'm particularly interested in support for .cjs config because all my projects have "type": "module" in package.json. But when changing the sample provided "rspack.config.js" (with no requires or imports) to "rspack.config.cjs", then I get the following:

TypeError: Cannot read properties of undefined (reading 'import') at getNormalizedEntryStatic (/var/www/rspack-project/node_modules/@rspack/core/src/config/normalization.ts:202:33) at getNormalizedRspackOptions (/var/www/rspack-project/node_modules/@rspack/core/src/config/normalization.ts:32:7) at createCompiler (/var/www/rspack-project/node_modules/@rspack/core/src/rspack.ts:55:44) at create (/var/www/rspack-project/node_modules/@rspack/core/src/rspack.ts:141:20) at rspack (/var/www/rspack-project/node_modules/@rspack/core/src/rspack.ts:165:31) at RspackCLI.createCompiler (/var/www/rspack-project/node_modules/@rspack/cli/src/rspack-cli.ts:49:26) at Object.handler (/var/www/rspack-project/node_modules/@rspack/cli/src/commands/build.ts:94:22)

[hardfist]

@wernerbihl .cjs is supported

[hardfist]

@fi3ework prebundle may meet lots of issue like web-infra-dev/modern.js#3338 when used in monorepo, if we bundle code in other package it will cause the bundled config can't find the its dependencies, so we think transformer is less prone

[fi3ework]

Prebundling could externalize bare imports, which would skip libraries in a monorepo, but still will meet type: module/commonjs issues.

[hardfist]

if config a in packageA use source b in packageB which has dependency c, when we do prebundle it will cause b is bundled in bundled_a file which is in packageB, then we do resolve dependency in bundle_a it will resolve failed because lies in packageB's node_modules other than packageA's node_modules

packageA
  config_a 
packageB
  b -> require('c')
  node_modules/c

when bundled config_a it will becomes

packageA
  config_a
  bundled_config_a -> require('c')
packageB
  b
  node_modules/c

then require('c') will failed because packageA doesn't have c in node_modules

[fi3ework]

Yes, it will. I was trying to say that making bare import externalized will keep resolving 'c' from B, which is how Vite behaves now. But that will not work for loading ts in other monorepo package. Using a transformer could be a more powerful solution.

[hardfist]

Yes, it will. I was trying to say that making bare import externalized will keep resolving 'c' from B, which is how Vite behaves now. But that will not work for loading ts in other monorepo package. Using a transformer could be a more powerful solution.

then we will stick to transformer solution for now and may use rspack itself to transform config one day.

[hardfist]

closed as not planned