Bun + Vite + TS (test)

How far can we get with bun :eyes:

Status

Does not work yet. child_process blocks esbuild. If the import is temporarily removed, the CLI exits on execute without messages, and Vite's JavaScript API doesn't run because http isn't implemented.

Results

Bun does not work with Vite yet, not to mention that it has to work with esbuild, rollup, and postcss first, which are major tools that Vite uses under the hood. However this experiment uncovers features needed if it were to work in Vite itself.

Below are a list of issues found, though you can see the finer changes in the patch made.

• http, http2, https not implemented.
• child_process not implemented. Blocks esbuild.
• Regex negative lookbehind not supported in JSC. PITA to refactor.
• When const require = createRequire() exists, bun treats the file as CJS, transpiling imports to require(), but because const require is declared late, it gives ReferenceError: Cannot access uninitialized variable. Can be workaround by avoiding require and rename as _require. https://github.com/oven-sh/bun/issues/453
• Dynamic import() doesn't execute file, as if a no-op.
• ESM imports aren't hoisted.
• process.stdout not implemented.
• path.posix not implemented. Can be polyfilled with path.posix = path but works with posix env only.
• fileUrlToPath doesn't accept file:// strings. Can be fixed by wrapping new URL(<string>).
• createRequire doesn't work correctly with file:// strings. URL however works correctly, and can be fixed by wrapping new URL(<string>).
• process assignment like process.env.NODE_ENV = '<string>' shouldn't be replaced. Can be workaround by wrapping eval().
• performance and perf_hooks not implemented. Can be polyfilled with globalThis.performance.
• self not implemented. Can be polyfilled with globalThis.self = globalThis.
• readline not implemented.

Notes

• Tried bun-utilities to polyfill child_process for esbuild. I'm not sure if it's 100% compatible, if comparing to esbuild's usage. (See esbuild temp patch)
• Since bun 0.1.6, running dev gives SyntaxError: Cannot declare a const variable twice: '__require' even if __require is only declared once.
• Since bun 0.1.6, accessing require('events').EventEmitter gives SyntaxError: Importing binding name 'EventEmitter' is not found.. Only happened recently, but the issue may have been hidden before.

Development

# Install dependencies (patch-package doesn't work with bun install)
$ npm install

# Run Vite with bun
$ npm run dev

# Run Vite with node
$ npm run node-dev

The goal is to make sure any changes made to satisfy bun still works in node.

License

MIT