**Describe the bug** `if (filename == null) return { code: content };` in [svelte-preprocess/src/transformers/typescript.ts](https://github.com/sveltejs/svelte-preprocess/blob/main/src/transformers/typescript.ts) line 497 is the issue. **To Reproduce** Call `svelte.preprocess(code, processor)` manually without providing the third optional parameter ( omitting the filename ) https://github.com/wangjia184/svelte-parser/blob/master/src/worker.ts (not mine, not small) **Expected behavior** when inputing `const x : number = 1` the output to be `const x = 1`, even when no filename was provided. **Additional context** When you provide a weird filename like `" "` then the preprocessor will work and remove the type annotations.