TypeScript

[stoically]

Why

• Codebase grows and staying maintainable gets harder, TS arguably makes it easier
• Better contracts between Background and UI

Evaluation

Transpiler

tsc

• typechecking and transpiling from the same lib
• official
• no babel plugins

babel-plugin-transform-typescript

• no type checking, must be done with tsc
• not official
• supports plugins

Linting

• tslint (deprecated in favor of eslint)
• eslint with typescript-eslint

Bundling

• parcel1
  • uses tsc by default, but without type checking and runs the result through babel
  • allows using babel with parcel-plugin-babel-typescript
  • typechecking with parcel-plugin-typescript seems to be broken
• parcel2 (currently in alpha)
  • uses babel-plugin-transform-typescript by default
  • has the option to use tsc by installing @parcel/transformer-typescript-tsc

Workarounds

UI

• Until there's a way to typecheck .vue files with parcel, the script portion is externalized into .ts files so they can be typechecked directly with tsc. That needs to be done with import instead of using the script src tag directly since that's not supported in parcel yet
• parcel2 will automatically code split common libraries, until then the building will include all imported vendor libs in the options and popup bundle, because it's not easily possible to dynamically import() Vue without doing dirty stuff like passing it down the components as prop
• Funfact: vue 3.0 will be a rewrite in TypeScript

Decisions

• Linting: typescript-eslint and tsc
• Bundling: parcel1 with tsc

Todo

• Background
• UI
• Tests