Last Call Webpack Plugin

3.0.0 verified Sat Apr 25 auth: no javascript

A Webpack plugin that allows transforming/modifying assets just before Webpack emits them. Version 3.0.0 supports Webpack 4+, while v2.1.2 is for Webpack 3 and below. The plugin accepts an array of asset processors, each with a regex to match asset names and a processor function returning a Promise. It provides an assets object for adding, deleting, or retrieving assets during processing. Useful for prefixing comments, running final optimizations (e.g., cssnano), or generating additional assets like source maps. Compared to other asset modification plugins, it offers explicit per-processor phase control and direct asset manipulation.

Common errors

error TypeError: LastCallWebpackPlugin is not a constructor ↓

cause Using ESM import syntax with CommonJS-only module.

fix

Use require('last-call-webpack-plugin') instead of import.

error Error: webpack v4+ only supports last-call-webpack-plugin@3 ↓

cause Trying to use v2 with Webpack 4 or v3 with Webpack 3.

fix

Match plugin version to Webpack version: v2 for Webpack 3, v3 for Webpack 4+.

error TypeError: asset.source is not a function ↓

cause processor receives webpack asset object, which may not have source() in older webpack versions or custom asset types.

fix

Check if asset.source exists, or use asset.buffer()/asset.content() depending on Webpack version.

Warnings

breaking v3.0.0 requires Webpack 4 or higher; v2.x for Webpack 3 and below. ↓

fix Downgrade to last-call-webpack-plugin@2.1.2 if using Webpack < 4.

deprecated Option phase: 'compilation.optimize-chunk-assets' may be deprecated in Webpack 5. ↓

fix Consider using 'compilation.optimize-assets' or 'emit' phase instead.

gotcha processor function must return a Promise or a value (if synchronous). Asynchronous behavior relies on Promise. ↓

fix Ensure processor returns a Promise or use async/await. For synchronous transforms, wrap in Promise.resolve().

gotcha The assets setAsset() method with null deletes the asset; does not provide feedback if asset missing. ↓

fix Use getAsset() to check existence before deleting, or catch errors.

Install

npm install last-call-webpack-plugin

yarn add last-call-webpack-plugin

pnpm add last-call-webpack-plugin

Imports

LastCallWebpackPlugin
wrong
```
import LastCallWebpackPlugin from 'last-call-webpack-plugin';
```
correct
```
const LastCallWebpackPlugin = require('last-call-webpack-plugin');
```
Package uses CommonJS export; ESM import may fail in Node without a bundler. Use require() in Webpack config.
LastCallWebpackPlugin (ESM)
wrong
```
const { LastCallWebpackPlugin } = require('last-call-webpack-plugin');
```
correct
```
import LastCallWebpackPlugin from 'last-call-webpack-plugin';
```
If using ESM with bundler (e.g., Webpack itself), default import works. Do not destructure named export.
Constructor options
wrong
```
new LastCallWebpackPlugin(assetProcessors: [...])
```
correct
```
new LastCallWebpackPlugin({ assetProcessors: [...], canPrint: true })
```
Options must be passed as an object with key 'assetProcessors'; the constructor expects an options object.

Quickstart

Shows typical usage with two processors: one to prepend a comment to JS files, another to minify CSS files using cssnano.

const LastCallWebpackPlugin = require('last-call-webpack-plugin');
const cssnano = require('cssnano');

module.exports = {
  entry: './src/index.js',
  output: {
    path: __dirname + '/dist',
    filename: 'bundle.js'
  },
  plugins: [
    new LastCallWebpackPlugin({
      assetProcessors: [
        {
          regExp: /\.js$/,
          processor: (assetName, asset) => Promise.resolve('// Author: John Doe\n' + asset.source())
        },
        {
          regExp: /\.css$/,
          processor: (assetName, asset, assets) => cssnano.process(asset.source()).then(r => r.css)
        }
      ],
      canPrint: true
    })
  ]
};