evanw/esbuild v0.14.7

on GitHub

Cross-module inlining of TypeScript enum constants (#128)

This release adds inlining of TypeScript enum constants across separate modules. It activates when bundling is enabled and when the enum is exported via the export keyword and imported via the import keyword:

// foo.ts
export enum Foo { Bar }

// bar.ts
import { Foo } from './foo.ts'
console.log(Foo.Bar)

The access to Foo.Bar will now be compiled into 0 /* Bar */ even though the enum is defined in a separate file. This inlining was added without adding another pass (which would have introduced a speed penalty) by splitting the code for the inlining between the existing parsing and printing passes. Enum inlining is active whether or not you use enum or const enum because it improves performance.

To demonstrate the performance improvement, I compared the performance of the TypeScript compiler built by bundling the TypeScript compiler source code with esbuild before and after this change. The speed of the compiler was measured by using it to type check a small TypeScript code base. Here are the results:

As you can see, enum inlining gives around a 15% speedup, which puts the esbuild-bundled version at the same speed as the offical TypeScript compiler build (the tsc column)!

The specifics of the benchmark aren't important here since it's just a demonstration of how enum inlining can affect performance. But if you're wondering, I type checked the Rollup code base using a work-in-progress branch of the TypeScript compiler that's part of the ongoing effort to convert their use of namespaces into ES modules.

Mark node built-in modules as having no side effects (#705)

This release marks node built-in modules such as fs as being side-effect free. That means unused imports to these modules are now removed when bundling, which sometimes results in slightly smaller code. For example:

// Original code
import fs from 'fs';
import path from 'path';
console.log(path.delimiter);

// Old output (with --bundle --minify --platform=node --format=esm)
import"fs";import o from"path";console.log(o.delimiter);

// New output (with --bundle --minify --platform=node --format=esm)
import o from"path";console.log(o.delimiter);

Note that these modules are only automatically considered side-effect when bundling for node, since they are only known to be side-effect free imports in that environment. However, you can customize this behavior with a plugin by returning external: true and sideEffects: false in an onResolve callback for whatever paths you want to be treated this way.

Recover from a stray top-level } in CSS (#1876)

This release fixes a bug where a stray } at the top-level of a CSS file would incorrectly truncate the remainder of the file in the output (although not without a warning). With this release, the remainder of the file is now still parsed and printed:

/* Original code */
.red {
  color: red;
}
}
.blue {
  color: blue;
}
.green {
  color: green;
}

/* Old output (with --minify) */
.red{color:red}

/* New output (with --minify) */
.red{color:red}} .blue{color:#00f}.green{color:green}

This fix was contributed by @sbfaulkner.