oven-sh/bun bun-v0.0.26

Bun v0.0.26

on GitHub

Features

Bun Macro

Bun Macros are a simple way to move code snippets from runtime to build-time.

Use them for:

• Zero runtime CSS-in-JS (or a little runtime, up to you)
• GraphQL parsing
• Static data fetching without a library (similar to Next.js' getStaticProps but from any file instead of just pages)
• you can come up with more use cases

This API (and implementation) is very new and I want to hear feedback on what to change.

How to use macros:

• Any import that starts with macro: is imported as a macro. Macros can be npm packages, local files, or anything else resolvable. These imports are always removed from the final output.
• Imports must be a named import, and are matched against call expressions (function calls) and template literals. JSX props may be added in a future release

Here's a quick example of using a macro:

// This import won't exist at runtime!
import { matchInFile } from "macro:./matchInFile";

export const IPAddresses = () => (
  <div>
    <h2>recent ip addresses</h2>
    <div className="Lines">
      {/* matchInFile gets inlined into an array at compile time */}
      {matchInFile("access.log", /^(?:[0-9]{1,3}\.){3}[0-9]{1,3}/).map(
        (ipAddress, index) => (
          <div className="Line" key={index}>
            {ipAddress}
          </div>
        )
      )}
    </div>
  </div>
);

The transpiled output looks something like this:

export const IPAddresses = () => jsx("div", {
    children: [
      jsx("h2", {
        children: ["recent ip addresses"]
      }, undefined, true, {}, this),
      jsx("div", {
        className: "Lines",
        children: [[
          "98.210.28.6",
          "192.99.4.168",
           // ... rest of the array 
       ].map((ipAddress, index) => jsx("div", {
          className: "Line",
          children: [ipAddress]
        }, index, true, {}, this))]
      }, undefined, true, {}, this)
 // ...rest of code
    ]
});

There are a few examples of how to write macros in https://github.com/Jarred-Sumner/bun/tree/main/examples/macros, but I will write more docs once I'm a little more confident that the API isn't going to change. Once I write macros for Relay and Emotion, I'll have a better sense for if this API is good enough or if there are changes to make.

I might change the import prefix from macro: to bun: because it's shorter and slightly faster to check (one u32 instead of a u32 and then a u16)

Credits

Bun Macros are inspired by babel-plugin-macros, which was Sunil Pai's idea. They're also sort of similar to Zig's comptime feature.

Bun.js

• Bun.readFileAsBytes and Bun.readFile now accept an array of paths to join. Both of these are valid:

Option A:

Bun.readFile(Bun.cwd + "file.txt");

Option B:

Bun.readFile([Bun.cwd, "./text/", "file.txt"]);

Unlike Node.js' path.join, it's an explicit array instead of arguments because someday, we might want to add extra options to this function.

Bug fixes

• Thanks @alexkuz for adding a check to the Makefile that necessary dependencies are installed prior to compiling Bun.
• Fixed an occasional UTF-8 decoding bug in Response.text() (from fetch)
• Fixed an edgecase in the URL parser where it would sometimes erroneously report the pathname as /
• Fixed a typo in the error thrown when you pass a blank string to fetch
• fetch now includes a User-Agent header by default. This is overridable, but it defaults to Bun.js v0.0.version-number