Customize @babel/plugin-transform-typescript options

[IlyaSemenov]

I would like to be able to pass custom options to @babel/plugin-transform-typescript

In particular, for interoperability reasons, I need to support declare x: string class members, and for that I need to use this:

['@babel/transform-typescript', { allowDeclareFields: true }]

However, it doesn't seem to be possible to achieve with opts.babel. It's not even possible to disable opts.ts and re-apply the same plugins manually because you only push custom plugins and one of them must be unshifted:

jiti/src/babel.ts

Lines 21 to 26 in f25960a

	if (opts.ts) {
	_opts.plugins!.push(require('@babel/plugin-transform-typescript'))
	// `unshift` because this plugin must come before `@babel/plugin-syntax-class-properties`
	_opts.plugins!.unshift([require('@babel/plugin-proposal-decorators'), { legacy: true }])
	_opts.plugins!.push(require('babel-plugin-parameter-decorator'))
	}

jiti/src/babel.ts

Lines 33 to 35 in f25960a

	if (opts.babel && Array.isArray(opts.babel.plugins)) {
	_opts.plugins?.push(...opts.babel.plugins)
	}

Basically I have to copy/paste the entire babel.ts in order to setup typescript options.

Suggestions

1. opts.ts to support not only boolean but also object with @babel/transform-typescript options
2. opts.babel to support not only subset of options but also a config customization callback which will be called directly before transformSync

[pi0]

Thanks for describing issue. allowDeclareFields is enabled in the 1.10.0 since babel 8 will enable it by default too (for nuxt you can recreate lockfile or use yarn upgrade nuxt).

• Supporting plugin options can be a good idea but I need more specific reasons to support them.
• Supporting babelrc and callback function per transform is dangerous since we cannot predict cache key anymore

Feel free opening more issues if anything else was missing.

[IlyaSemenov]

@pi0 It now crashes with:

   ╭────────────────────────────────────────────────────────────────────────────────────────────────╮
   │                                                                                                │
   │   ✖ Nuxt Fatal Error                                                                           │
   │                                                                                                │
   │   Error: UNKNOWN_PLUGIN_PROPERTY: [BABEL] .allowDeclareFields is not a valid Plugin property   │
   │   /Users/semenov/work/eg11/eg11-web/src/frontend/nuxt.config.ts:0:0                            │
   │                                                                                                │
   ╰────────────────────────────────────────────────────────────────────────────────────────────────╯

See my comment in 914499c

[pi0]

Fixed in 0.10.1