Custom extension for Text Loader

[robobun]

I would like to be able to import .env.example files with the standard module import syntax:

import whatever from './.env.example';

I tried to use a custom loader:

import { plugin } from "bun";

plugin({
  name: "Env",
  async setup(build) {
    build.onLoad({ filter: /\.env\.example/ }, async (args) => {
      return {
        contents: await Bun.file(args.path).arrayBuffer(),
        loader: 'text',
      };
    })
  },
});

Which resulted in the following error:

error: Expected loader to be one of "js", "jsx", "object", "ts", "tsx", "toml", or "json"
error: script "dev:build" exited with code 1 (SIGHUP)
This error seems to come from the Module Loader itself: https://github.com/oven-sh/bun/blob/main/src/bun.js/bindings/ModuleLoader.cpp#L225
The Loader class for bun-types lists text as an option: https://github.com/oven-sh/bun/blob/main/packages/bun-types/bun.d.ts#L3073
It may also look as text isn't listed on the runtime plugin documentation: https://github.com/oven-sh/bun/blob/main/docs/runtime/plugins.md?plain=1#L269

Originally reported on Discord: Custom extension for Text Loader

[joshkolenko]

@robobun You can achieve this by returning an object with an exports property and the loader set to object. The export will then be treated as an ES module.

For example:

import { plugin } from "bun";

plugin({
  name: "Env",
  async setup(build) {
    build.onLoad({ filter: /\.env\.example/ }, async (args) => {
      return {
        exports: { default: await Bun.file(args.path).arrayBuffer() },
        loader: 'object',
      };
    })
  },
});

[Jarred-Sumner]

You can do bun --loader:.html:text ./input.js