TypeScript erasableSyntaxOnly Codemod #

Disclaimer: This is under very initial development and is not ready at all for use. Contributions and feedback are very welcome though 🙌

Hi! This is tsec, a third-party codemod tool for automatically migrating your code to be compatible with TypeScript's erasableSyntaxOnly flag.

The assumptions and opinions related to the changes that will be made are described in assumptions.md.

Not supported #

I'm personally unaware of scenarios where either of these would be intentionally included patterns, so am taking the approach of leaving them for typescript to error on. If however you'll need a codemod from one of these, please feel free to make an issue.

• namespaces and modules with runtime code
• Non-ECMAScript import = and export = assignments

// ❌ error: An `import ... = require(...)` alias
import foo = require("foo");
// ❌ error: A namespace with runtime code.
namespace container {
  foo.method();
  export type Bar = string;
}
// ❌ error: An `import =` alias
import Bar = container.Bar;

TODO #

• Handle multiple files with glob input
• Write a cli for running the codemod with options for picking which transformations to run on
• CLI should warn about tsconfig updates and docs to be aware of
  • https://nodejs.org/api/typescript.html#type-stripping
• CLI about how to fix imports for verbatimModuleSyntax
  • opting not to support this to encourage the use of auto-fixing lint rules
  • https://typescript-eslint.io/rules/consistent-type-imports
  • https://biomejs.dev/linter/rules/use-import-type/
• Support monorepos