When Svelte met TypeScript feat. Rich Harris and Orta Therox

For a long time, TypeScript support was one of the most requested  features in Svelte. People like being able to write the JavaScript inside the components. We  have this single file component format. But at the time, TypeScript was becoming incredibly popular  and very important in the JavaScript ecosystem. To the extent that a lot of people just  won't touch code unless it's TypeScript. And so it was preventing people from using Svelte.

I happen to know Orta. He's a good friend. He  actually used to live down the road from here, and he's on the TypeScript team. And Orta was  able to lead a project with several developers to actually build TypeScript support into Svelte.  Not directly into the compiler, you still have to add a little bit of a preprocessor, but it means  that now if you're building a Svelte component, you can use TypeScript and you will get  all of the same auto-completions and type checking as you're building your app as you  would if you're writing straight TypeScript.

I heard about Svelte back at my old company. We  had Rich Harris come in and give us a talk about what it was. It was still like a very new project  for him at the time. And a few years later, I interacted with Rich a few times through the  JavaScript ecosystem in New York. We are both Englishmen living in New York. And I invited  him to a house party, and we were chatting about where Svelte is and where Svelte could be  and at the time I was working on TypeScript and

I thought it would be a very interesting sort  of exploration to see what it looks like to make the sort of tooling experience that we have  in TypeScript as good in the Svelte ecosystem, because Rich hadn't really been focusing much  on what does it look like to work in Svelte in your editor but mostly on what is Svelte,  how does Svelte work and how does Svelte fast. And so I felt like it was something that  I could take a dig at. I had a lot of

experience in trying to make developer  tools for complicated environments, and so I said Well, maybe I could try and  take that responsibility for you for a while. Like we didn't want to TypeScript inside  Svelte, but we wanted the TypeScript-like experience that people get in their editors for  Svelte. I think that that is like an important part of scaling Svelte. Like the ability to  have your editor tell you what properties are available and how they all intermingle. You need  like rich developer tools to be able to do that.

I kind of did two things. One was to  describe what I think the future of tooling for Svelte looks like. And  then the other was to sort of create the foundations that the allow of a  people to eventually create those. There were a lot of different projects  that had different owners that weren't necessarily on the Svelte call  team. They were all trying to find different ways that you could have  interesting experiences in the browsers,

in your editors and on the command line. What  I did was I went and consolidated all of the most interesting work into a single place  and started building out these foundations that would allow maintainers in the call team to  stop actually running these projects themselves. So think of it as like you know, there were a lot  of people exploring in the world. I came in as a sort of somebody that has a lot of experience  in that area and just said, these projects are the ones that we actually want to take. We'll  take some of these projects and put them into

Svelte sort of repository of things that we care  about and make a few more people call team members because they're already doing interesting work  and then consolidate it all into one single thing. We actually built support for Svelte in an LSP,  which means that it works in VM it works in Atom, it works in Sublime Text, and it works in  VS code as well as trying to figure out, Well, we may have all these tools in your editor,