Now implemented, please provide feedback

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Original Post

The language-server has quite a few features by now. What's missing for the complete developer experience and intellisense though is crossing the boundaries of Svelte and JS/TS files. This can be achieved through a TypeScript plugin. The following features would be cool to have:

• Rename variables in Svelte files, too, when renaming starts in a TS/JS file
• Go to Svelte definition/file from a TS/JS file
• Find references
• Better diagnostics (TS: Named export from module script not recognized #550)

Open Questions

• How to connect the plugin to the running language server?
• A TypeScript plugin has to be synchronous because all language service methods are synchronous. Our code is asynchronous because of the Source Mapping initialization. How to work around that?