https://github.com/bitjson/shake-default-params
Testing dead-code elimination of unused default parameters in all known JS bundlers
https://github.com/bitjson/shake-default-params
dead-code-elimination esbuild parcel rollup tree-shaking webpack
Last synced: 3 months ago
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Testing dead-code elimination of unused default parameters in all known JS bundlers
- Host: GitHub
- URL: https://github.com/bitjson/shake-default-params
- Owner: bitjson
- Created: 2022-04-15T19:28:46.000Z (about 3 years ago)
- Default Branch: main
- Last Pushed: 2022-05-17T16:13:02.000Z (about 3 years ago)
- Last Synced: 2025-01-14T06:47:09.652Z (4 months ago)
- Topics: dead-code-elimination, esbuild, parcel, rollup, tree-shaking, webpack
- Language: JavaScript
- Homepage:
- Size: 78.1 KB
- Stars: 0
- Watchers: 2
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: readme.md
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README
# Tree-Shaking Default Parameters
This demo tests how various bundlers handle [Libauth](https://github.com/bitauth/libauth/)'s WebAssembly crypto implementations (`ripemd160`, `sha1`, `sha256`, `sha512`, and `secp256k1`).
As a [pure ESM library](https://gist.github.com/sindresorhus/a39789f98801d908bbc7ff3ecc99d99c), Libauth v2 can asynchronously instantiate each WASM implementation internally, exporting simple interfaces that behave like collections of JS-only functions (with better performance).
Many of Libauth's exported functions also use one of these built-in WASM instances as a default parameter. For example, `decodeBase58Address` has the definition:
```ts
export const decodeBase58Address = (
address: string,
sha256: { hash: (input: Uint8Array) => Uint8Array } = internalSha256
) => {
// ...
};
```
Most applications can call `decodeBase58Address(address)` to automatically use the default, WASM-based `sha256` implementation (`internalSha256`). See [`src/app-default.js`](./src/app-default.js).
Applications that already have another `sha256` implementation can provide that implementation as the second parameter: `decodeBase58Address(address, mySha256Implementation)`. In this case, the default parameter (`internalSha256`) is dead code and should be possible to eliminate from the application's bundle (commonly called [tree shaking](https://developer.mozilla.org/en-US/docs/Glossary/Tree_shaking) in the JavaScript ecosystem). See [`src/app-shakable.js`](./src/app-shakable.js).
## Bundler Support
This repo tests dead-code elimination of unused default parameters as used in Libauth (with asynchronously instantiated WASM implementations): [`src/app-shakable.js`](./src/app-shakable.js).
Currently, **dead-code elimination of unused default parameters** is only supported by [Rollup](https://rollupjs.org/).
| Bundler | Support | Issue | PR |
| --------------------------------------- | :------------------------------------------------: | ------------------------------------------------------------------------------------ | ------------------------------------------------------------------ |
| [`esbuild`](https://esbuild.github.io/) | ❌ ([example](./bundlers/esbuild/app-shakable.js)) | [`evanw/esbuild#2185`](https://github.com/evanw/esbuild/issues/2185) | - |
| [`parcel`](https://parceljs.org/) | ❌ ([example](./bundlers/parcel/app-shakable.js)) | [`parcel-bundler/parcel#7961`](https://github.com/parcel-bundler/parcel/issues/7961) | - |
| [`rollup`](https://rollupjs.org/) | ⏳ ([example](./bundlers/rollup/app-shakable.js)) | [`rollup/rollup#4466`](https://github.com/rollup/rollup/issues/4466) | [`rollup/rollup#4498`](https://github.com/rollup/rollup/pull/4498) |
| [`terser`](https://terser.org/) | ❌ ([example](./bundlers/terser/app-shakable.js)) | [`terser/terser#1199`](https://github.com/terser/terser/issues/1199) | - |
| [`webpack`](https://webpack.js.org/) | ❌ ([example](./bundlers/webpack/main.mjs)) | [`webpack/webpack#15671`](https://github.com/webpack/webpack/issues/15671) | - |
This simpler example may also be useful for quickly testing support in bundlers:
`package.json`:
```json
{
"type": "module"
}
```
`module.js`:
```js
// should not appear in bundle:
const internalAdd = (a, b) => (a === '0' ? b : a + b);
export const addAndLog = (a, b, impl = internalAdd) => console.log(impl(a, b));
```
`app.js`:
```js
import { addAndLog } from './module.js';
const myAdd = (a, b) => a + b;
addAndLog(1, 2, myAdd); // => 3
```