How does Bun's bundler handle file types like JSON and TOML

Bun's Built-in Loaders

Bun uses the file extension to determine which built-in loader should be used to parse the file. Every loader has a name, such as `js`, `tsx`, or `json`. These names are used when building plugins that extend Bun with custom loaders[1].

JSON Loader

JSON files can be directly imported. Bun will parse them with its fast native JSON parser[1].

js
import config from "./config.json";
config.logLevel; // => "debug"

During bundling, the parsed JSON is inlined into the bundle as a JavaScript object[1].

js
var config = {
  logLevel: "debug",
  // ...other fields 
};
config.logLevel;

If a `.json` file is passed as an entrypoint, it will be converted to a `.js` module that `export default`s the parsed object[1].

TOML Loader

TOML files can be directly imported. Bun will parse them with its fast native TOML parser[1].

js
import config from "./bunfig.toml";
config.logLevel; // => "debug"

During bundling, the parsed TOML is inlined into the bundle as a JavaScript object[1].

js
var config = {
  logLevel: "debug",
  // ...other fields
};
config.logLevel;

If a `.toml` file is passed as an entrypoint, it will be converted to a `.js` module that `export default`s the parsed object[1].

In addition to the usual suspects like TypeScript and JSX, the Bun bundler handles more interesting cases like JSON and TOML, which will be inlined into the bundle[2].