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The Betaflight App Is Adopting TypeScript, Incrementally

· 2 min read
blckmn
blckmn
Developer

The Betaflight App is now type-checked. Three TypeScript files had already made their way into the tree over the past fortnight, but nothing was checking them: Vite quietly stripped the types and moved on. With #5503 the repository has a tsconfig.json, vue-tsc runs as part of npm run lint, and ESLint understands .ts files and <script setup lang="ts"> blocks. CI and the pre-commit hook gate on it like they do on lint.

Why​

The app talks to the flight controller through a large, loosely typed object graph: the FC state, MSP replies, CLI output. Most of the bugs we chase are shape mismatches: a field that moved, a null nobody handled, a wire format that changed. Last week a port-annotation feature was built against a function mask the firmware had already stopped sending; the code was fine, the assumption was not. Types make those assumptions visible, and the compiler enforces them on every refactor rather than relying on grep.

The Approach​

  • No rewrite. src/js (MSP, FC, serial) stays JavaScript. Users see no change.
  • New code is TypeScript, as .ts files or <script setup lang="ts">, in strict mode from day one.
  • Legacy JavaScript is importable, not judged. allowJs lets TypeScript consume it; checkJs: false means it is not type-checked. Where TS needs a shape from a JS module, a JSDoc @type on that module is enough.
  • Convert as you touch. A composable or store you materially change may be converted in the same pull request, one file per PR so reviews stay small.
  • Ratchet later. Once enough of a folder is TypeScript, allowJs is switched off there and the FC state gets a sealed interface. That is the next phase, tracked in the repository's AGENTS.md.

For Contributors​

Nothing changes in how you build or run the app. npm run lint now includes the type-check; npm run typecheck runs it alone. If you open a pull request that adds a JavaScript file where a TypeScript one would do, expect a reviewer to ask for the .ts version.

Questions and discussion are welcome in the development channels on the Betaflight Discord.