esbuild 0.14.26

v0.14.26

on Node.js NPM

Fix a tree shaking regression regarding var declarations (#2080, #2085, #2098, #2099)

Version 0.14.8 of esbuild enabled removal of duplicate function declarations when minification is enabled (see #610):

// Original code
function x() { return 1 }
console.log(x())
function x() { return 2 }

// Output (with --minify-syntax)
console.log(x());
function x() {
  return 2;
}

This transformation is safe because function declarations are "hoisted" in JavaScript, which means they are all done first before any other code is evaluted. This means the last function declaration will overwrite all previous function declarations with the same name.

However, this introduced an unintentional regression for var declarations in which all but the last declaration was dropped if tree-shaking was enabled. This only happens for top-level var declarations that re-declare the same variable multiple times. This regression has now been fixed:

// Original code
var x = 1
console.log(x)
var x = 2

// Old output (with --tree-shaking=true)
console.log(x);
var x = 2;

// New output (with --tree-shaking=true)
var x = 1;
console.log(x);
var x = 2;

This case now has test coverage.

Add support for parsing "instantiation expressions" from TypeScript 4.7 (#2038)

The upcoming version of TypeScript now lets you specify <...> type parameters on a JavaScript identifier without using a call expression:

const ErrorMap = Map<string, Error>;  // new () => Map<string, Error>
const errorMap = new ErrorMap();  // Map<string, Error>

With this release, esbuild can now parse these new type annotations. This feature was contributed by @g-plane.

Avoid new Function in esbuild's library code (#2081)

Some JavaScript environments such as Cloudflare Workers or Deno Deploy don't allow new Function because they disallow dynamic JavaScript evaluation. Previously esbuild's WebAssembly-based library used this to construct the WebAssembly worker function. With this release, the code is now inlined without using new Function so it will be able to run even when this restriction is in place.

Drop superfluous __name() calls (#2062)

When the --keep-names option is specified, esbuild inserts calls to a __name helper function to ensure that the .name property on function and class objects remains consistent even if the function or class name is renamed to avoid a name collision or because name minification is enabled. With this release, esbuild will now try to omit these calls to the __name helper function when the name of the function or class object was not renamed during the linking process after all:

// Original code
import { foo as foo1 } from 'data:text/javascript,export function foo() { return "foo1" }'
import { foo as foo2 } from 'data:text/javascript,export function foo() { return "foo2" }'
console.log(foo1.name, foo2.name)

// Old output (with --bundle --keep-names)
(() => {
  var __defProp = Object.defineProperty;
  var __name = (target, value) => __defProp(target, "name", { value, configurable: true });
  function foo() {
    return "foo1";
  }
  __name(foo, "foo");
  function foo2() {
    return "foo2";
  }
  __name(foo2, "foo");
  console.log(foo.name, foo2.name);
})();

// New output (with --bundle --keep-names)
(() => {
  var __defProp = Object.defineProperty;
  var __name = (target, value) => __defProp(target, "name", { value, configurable: true });
  function foo() {
    return "foo1";
  }
  function foo2() {
    return "foo2";
  }
  __name(foo2, "foo");
  console.log(foo.name, foo2.name);
})();

Notice how one of the calls to __name is now no longer printed. This change was contributed by @indutny.