import and export statements are core features of the JavaScript language. They were added as part of the ECMAScript Modules (ESM) specification, and now are generally available in most mainstream JavaScript environments, including all evergreen browsers and Node.js.

When writing TypeScript code with ESM, it can sometimes be desirable to import or export a type only in the type system. Code may wish to refer to a type, but not actually import or export a corresponding value.

Type-only imports and exports are not emitted as runtime code when code is transpiled to JavaScript. This brings up two questions:

• Why would you want to use these type-only imports and exports?
• How can you enforce a project use them whenever necessary?

Let's dig in!

Programmers who work with tools like ESLint and Prettier often refer to ASTs. But what is an AST, why is it useful for these kinds of tools, and how does that interact with ESLint and TypeScript tooling? Let's dig in!

The typescript-eslint website at https://typescript-eslint.io is the canonical location for documentation on how to use ESLint on TypeScript code. The site includes a documentation page for each of the over 100 ESLint rules exposed by its ESLint plugin. Each of those rule docs pages includes a description of the rule, any options it allows, links to its source code, and other important information about its usage.

Until recently, keeping descriptions of rules consistent between their source code and docs pages was a cumbersome manual chore. We'd written a suite of Jest tests to verify they matched -- but those tests didn't capture everything, often failed with cryptic messages, and were missed by less experienced contributors.

We're happy to say that now, we've overhauled rule docs pages to automatically generate metadata information from rule source code. That means the pages always display up-to-date information without developers needing to manually rewrite docs on rule changes. Hooray! 🎉

This blog post gives an overview of the chore to generate rule docs options automatically.