babel-plugin-pure-calls-annotation

0.4.2 verified Sat Apr 25 auth: no javascript

A Babel plugin (v0.4.2, stable, low release cadence) that automatically adds /*#__PURE__*/ comments to call expressions in variable declarators, assignment expressions, call arguments, and other expression contexts. This helps bundlers like Webpack identify side-effect-free calls for tree shaking and dead code elimination. Unlike manual annotation, it eliminates human error and ensures consistent coverage across large codebases. Ships TypeScript types and integrates seamlessly into any Babel-based build pipeline.

Common errors

error SyntaxError: 'babel-plugin-pure-calls-annotation' threw an error: Cannot find module '@babel/core' ↓

cause Missing @babel/core as a peer dependency.

fix

npm install @babel/core --save-dev

error TypeError: Cannot read properties of undefined (reading 'callee') ↓

cause The plugin expects a Babel AST node with a callee property; corrupted or outdated Babel version may cause this.

fix

Update Babel to version 7.x or above and ensure the plugin is compatible.

error Error: Plugin/preset files are not allowed to export objects, only functions. ↓

cause This error occurs if the plugin is imported incorrectly (e.g., using named import instead of default).

fix

Use default import: import pureCallsAnnotation from 'babel-plugin-pure-calls-annotation'

Warnings

gotcha The plugin annotates all eligible call expressions, including those that may have side effects. Use with caution; only include if you are certain the annotated calls are pure. ↓

fix Manually verify or use other methods (e.g., /*#__PURE__*/ comments) to ensure purity.

breaking BREAKING: Version 0.4.0 changed annotation behavior for IIFEs: previously IIFEs were not annotated; now they are. ↓

fix If you rely on IIFEs not being annotated, downgrade to <0.4.0 or update your code to handle the change.

deprecated The plugin may not be actively maintained; last release was in 2021. Consider alternatives like manual annotation or custom Babel plugin for tree shaking. ↓

fix Review current tree shaking needs; use terser-webpack-plugin with sideEffects: false as a more maintained alternative.

gotcha Does not annotate call expressions in all positions (e.g., as standalone statements). Only variable declarators, assignment expressions, and call arguments are covered. ↓

fix Manually add /*#__PURE__*/ to unannotated pure calls or extend the plugin.

Install

npm install babel-plugin-pure-calls-annotation

yarn add babel-plugin-pure-calls-annotation

pnpm add babel-plugin-pure-calls-annotation

Imports

default

wrong

const pureCallsAnnotation = require('babel-plugin-pure-calls-annotation')

correct

import pureCallsAnnotation from 'babel-plugin-pure-calls-annotation'

Default import works in ESM; CommonJS require is also supported but discouraged for TypeScript

pureCallsAnnotation
```
import pureCallsAnnotation from 'babel-plugin-pure-calls-annotation'
```
Plugin is used as a Babel plugin, imported as default and passed to plugins array

BabelPluginPureCallsAnnotation

wrong

const { BabelPluginPureCallsAnnotation } = require('babel-plugin-pure-calls-annotation')

correct

import BabelPluginPureCallsAnnotation from 'babel-plugin-pure-calls-annotation'

Named export does not exist; only default export. Use default import.

Quickstart

Add the plugin to Babel config to automatically annotate pure call expressions with /*#__PURE__*/ for tree shaking.

// babel.config.js
module.exports = {
  plugins: [
    'babel-plugin-pure-calls-annotation'
  ]
};

// Input: const result = compute()
// Output: const result = /*#__PURE__*/compute()