Working TS compiler & AST type checker

[marcus-sa]

I've seen multiple requests for TypeScript support.

This can be done in a few ways:

1. Using the TS compiler API directly in the Svelte compiler for transforming scripts into components and then do type checking support against the template AST.
2. Writing a compiler specifically for TS on top of the Svelte compiler with integration for Rollup, Webpack & Bazel.

The second approach is something I've taken a shot at, quite successfully I must say.

The compiler transpiles all scripts into valid JS that the Svelte compiler can transform into components and then it creates declaration files for the components, that the type checking then can consume later on to validate the components and templates.
It saves the AST compilation in a cache which then later on, the TS type checker is used to validate everything.

What's your opinion on this?

The repository can be found at https://github.com/marcus-sa/svelte-ts

[swyxio]

related sveltejs/sapper#760 and #1639

[pngwn]

Yep, there is already an issue about this.

[marcus-sa]

Not really the same issue.
That issue only describes transpiling TypeScript in scripts, but not type checking or generation of component declarations.

Yeah, what you just linked to is such a small part of actually implementing TS support..

[marcus-sa]

So it really sounds like you guys don't care about TS support at ALL.
You decide to close a thread which identifies and tries to solve the issue, so that everyone can be happy with the tooling usage of Svelte.

Once you saw the title being named something with "TypeScript" you probably just closed it immediately.
It's understandable because people keep asking about it, but if you gave some answers then people wouldn't.

Should I continue this project to support TS fully, or are you planning to extend your compiler & checker with TS capabilities?
Just want to know whether or not I'm wasting my time.

[pngwn]

I didn't link any issues. I should have linked to the relevant issue and I apologise for that. The issue I was referring to is this: #1639

I closed it because we already have an issue to discuss TypeScript support. Comments relating to TS support in Svelte components, what it should cover and how it could or should be implemented, should be directed the existing issue.

We always close duplicate issues to reduce noise in the repository, having several issues for each feature request is not going to make dealing with them easier, however noteworthy the author thinks their issue is.

Regarding Typescript, people do ask about it frequently and we, almost as frequently, respond that there is an issue to track it, we haven't got around to it yet and when we have any updates we will share them. If someone else wants to take this on, we welcome contributions from the community.

[quantuminformation]

As a TS dev since 2012, I actually don't care about TS support given how much JS tooling has improved.

https://www.youtube.com/watch?v=xHI8S4gRQYg&t=4s

[marcus-sa]

@quantuminformation that's why I'm asking whether or not they're going to support it, or if I should continue on my own.
For me it doesn't really matter, I just want some clarification.

I only gotta take some precautions on whether or not the html AST is going to include breaking changes in the future.

[marcus-sa]

@pngwn cheers. I guess I'll continue my project then 😄
The issue you linked to is locked btw.

[quantuminformation]

There can’t be a definite answer now as there are still so many other priorities

On Thu, 10 Oct 2019 at 19:19, Marcus S. Abildskov ***@***.***> wrote: @quantuminformation <https://github.com/QuantumInformation> that's why I'm asking whether or not they're going to implement it, or if I should continue on my own. For me it doesn't really matter, I just want some clarification. — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#3677?email_source=notifications&email_token=AABU35VKMKSQUI7TJKB2JOLQN5W3PA5CNFSM4I7CKFK2YY3PNVWWK3TUL52HS4DFVREXG43VMVBW63LNMVXHJKTDN5WW2ZLOORPWSZGOEA5JCZY#issuecomment-540709223>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AABU35TQTXVUDSJY4ZGAL43QN5W3PANCNFSM4I7CKFKQ> .

-- Kind regards Nikos Katsikanis

[pngwn]

I did not realise that. I'll reopen this issue so further discussion on this solution can take place.

This isn't an invitation for everyone to ask 'is it ready yet', so let's keep things focused on the solution at hand.

There is definitely a desire for first-class typescript support, we don't necessarily have strong opinions on how that would work right now. As you can see from this comment this is something we want to do. But as you can also see from this comment we havent gotten around to it. Nothing has changed materially since the last comments in that issue were made.

[mindplay-dk]

2. Writing a compiler specifically for TS on top of the Svelte compiler with integration for Rollup, Webpack & Bazel.

Bazel 🤔 ... did you mean Babel?

[marcus-sa]

@mindplay-dk no I meant Bazel :)
The implementation was specifically made for Bazel, but the compiler and type checker will be decoupled so that they can be used for Webpack & Rollup as well.

https://asciinema.org/a/273603 👀