[WIP] Support for Ember

[gossi]

Hello,

this is some Ember folks seeking support to generate types for Ember's Template format with .gts file extension, so we can use tsdown for building Ember addons. Ember's tooling luckily already sits on top of Volar, with an API very similar to vue-tsc so we hope the integration is quite similar, too.

This is a draft PR, mostly for us to exchange comments on specific parts of the code. Formally finalizing the PR is to do, first goal is to make the code to work.

[gossi]

@machty Vue allows passing in TS as part of their API. Ember does search it by itself. Maybe not wrong to open up the API to accept TS and only search when it isn't provided?

[pkg-pr-new]

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npm i https://pkg.pr.new/rolldown-plugin-dts@131

commit: da3d324

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Diff	Package	Supply Chain Security	Vulnerability	Quality	Maintenance	License
	@​glimmer/​component@​2.0.0
	@​babel/​plugin-transform-typescript@​7.28.5
	@​rollup/​plugin-babel@​6.1.0
	@​glint/​ember-tsc@​1.0.7
	@​embroider/​addon-dev@​8.1.0
	ember-source@​6.8.1
	babel-plugin-ember-template-compilation@​3.0.1

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[sxzz]

Hi @gossi, is there any progress on this? If you'd like to continue with this PR, I’d be glad to accept it. Otherwise, would you mind closing it?

[gossi]

Sorry, I totally forgot about it. Thanks for the reminder.

The goal: Get type generation for ember going in oxc/rolldown environment

One More Try

I did in fact look into it again once more and noticed an issue. Given this input:

// main.ts
import { SuperTable } from './super-table.gts'

export { SuperTable }

I saw the following issue:

Error: Build failed with 1 error:

[plugin rolldown-plugin-dts:fake-js]
SyntaxError: Export 'SuperTable' is not defined. (1:9)

which is even more interesting, when I logged the code for that error:

export { SuperTable }

From here:

rolldown-plugin-dts/src/fake-js.ts

Lines 303 to 305 in f4d41b3

	const file = parse(code, {
	sourceType: 'module',
	})

So, we were wondering if there is some sort of "optimization" going on, that leads to a missing import statement?

Another Idea: ember rolldown plugin

Since I run into that issue, I came to the idea, to make a rolldown plugin for ember and then use it. Until now it is a rollup plugin with no-longer-needed compat. So getting rid of it and making it a rolldown plugin, using only the parts needed for now and using the filter mechanism to speed them up for use in rolldown. In essence it transforms .gts and .gjs files, to turn the <template> into proper JS. From there on, you can consider these files correct JS files. That went pretty straight forward, output is really good.

I wanted to have type generation, so I used it with tsdown which comes with this plugin already, turned dts on and boom, that blow up, because it didn't understand the .gts extension. I changed the plugin to rewrite .gts to .ts but not finding success that day.

You can read the full story here: embroider-build/embroider#2658

Discuss the Options

Remember the goal: Get type generation for ember going in oxc/rolldown environment

That still stands. I found another way, that gives a choice for finding a good strategy. On the technical level, performance is a very important factor here, as this is what oxc is all about.

Performance Considerations

• Rolldown plugins to use the filter property to speed up oxc tasks
• Rolldown plugins only for transform can take a narrow filter (only .gts/.gjs) for transform
• Rolldown plugins for transform and extension re-writing are more costly as they need to do more operations
• Type generation through tsgo is projectively the fastest
• Type generation through ember-tsc will put a slowing layer in the middle

With that in mind let's discuss the options.

1. ember rolldown plugin only

• Single package, less managing overhead
• Performance:
  • Rollup plugin: Feels like unnecessary transforms are needed (extension rewrite, slow filter)
  • Type generation: Excellent (tsgo ready, as long as the types are cool with that)

2. ember rolldown plugin + ember-tsc through rolldown-plugin-dts

• Multiple packages, managing overhead
• Performance:
  • Rollup plugin: Excellent
  • Type generation: ember-tsc middleware

3. ember rolldown plugin + rolldown-plugin-dts (Best of both worlds)

Is this possible?

• Single package, less managing overhead
• Performance:
  • Rollup plugin: Excellent
  • Type generation: Execllent

Well, that I haven't tried. That depends on the anwser to a question I have: Can rolldown-plugin-dts/Typescript treat additional file extensions as .ts and follow as usual?

• If the answer is yes: We can configure it as part of this plugin and we are good
• If the answer is no: Please help me find a good strategy for integration with the oxc/rolldown ecosystem.

Thanks a lot