Information

This PR allow passing custom swc configuration to swcPlugin to solves the following issues: #1291 #1104 #1311

I know this feature isn't aligned with the tsup philosophy to minimize the configuration, but there are some needs that legitimate to introduce swc option.

Maybe a better solution can be found based on this PR ;)

Usage

When you use legacy TypeScript decorator by enabling emitDecoratorMetadata in your tsconfig, tsup will automatically use SWC to transpile
decorators. In this case, you can give extra swc configuration in the tsup.config.ts file.

For example, if you have to define useDefineForClassFields, you can do that as follows:

import { defineConfig } from 'tsup'

export default defineConfig({
  entry: ['src/index.ts'],
  splitting: false,
  sourcemap: true,
  clean: true,
  swc: {
    jsc: {
      transform: {
        useDefineForClassFields: true
      }
    }
  }
})

Note: some SWC options cannot be configured:

{
  "parser": {
    "syntax": "typescript",
    "decorators": true
  },
  "transform": {
    "legacyDecorator": true,
    "decoratorMetadata": true
  },
  "keepClassNames": true,
  "target": "es2022"
}

You can also define a custom .swcrc configuration file. Just set swcrc to true
in tsup.config.ts to allow SWC plugin to discover automatically your custom swc config file.

import { defineConfig } from 'tsup'

export default defineConfig({
  entry: ['src/index.ts'],
  splitting: false,
  sourcemap: true,
  clean: true,
  swc: {
    swcrc: true
  }
})