CommonJS Tree Shaker plugin for Webpack
Please file an issue if anything is broken.
See common-shake for abstract bundler-independent implementation.
NOTE: webpack version 4 may be needed in order to run this.
If you're using webpack 3, please use webpack-common-shake@1.x.
NOTE: Logo is a modified version of webpack's logo
Why?
There are vast amount of CommonJS modules out there. Thus CommonJS Tree Shaking
is as important as the ESM module import/export shaking.
How?
This plugin removes unused assignments to exports properties leaving removal
of the (presumably) dead code to UglifyJS. If, for example, you had a module:
exports.used = 1;
var tmp = exports.unused = 2;
This plugin will transform it to:
exports.used = 1;
var tmp = 2;
It is up to UglifyJS (or some other optimizer) to decide, whether tmp is used
or not and delete it. Luckily it is much simpler for it to do if the uses are
not clouded by exporting the values.
Usage
Example webpack.config.js:
const ShakePlugin = require('webpack-common-shake').Plugin;
module.exports = [{
entry: 'entry.js'
output: {
path: 'dist',
filename: 'output.js'
},
plugins: [ new ShakePlugin() ]
}];
Demonstration
See webpack-common-shake-demo for size comparison of output with and
without this plugin.
Options
Plugin constructor accepts options object which may have following properties:
const plugin = new ShakePlugin({
warnings: {
global: true,
module: false
} /* default */,
// Invoked on every deleted unused property
onExportDelete: (resource, property) => {},
// See `Limitations` section for description
onModuleBailout: (module, bailouts) => { ... },
onGlobalBailout: (bailouts) => { ... }
});
Limitations
Although, generally this module works and helps removing unused code from the
bundles. There are some limitations that may prevent it from running either
partially or completely. Some examples are provided below, otherwise please use
common sense (or onModuleBailout, onGlobalBailout plugin options).
Some local (partial) bailouts:
- Dynamic exports
exports[Math.random()] = ... - Overriding imported vars
var a = require('./a'); a.lib; a = require('./b') - Using
requirein unknown wayconsole.log(require('./lib')) - Destructuring
requiredynamically{ [prop]: name } = require('./a') - Dynamic import
var fn = require('./lib')[Math.random()]
Some global (full) bailouts:
- Dynamic use of require
require(Math.random())
This plugin will print some webpack warnings. In any case, bailouts may be
obtained programmatically too:
const plugin = new ShakePlugin({
onModuleBailout: (module, bailouts) => { ... },
onGlobalBailout: (bailouts) => { ... }
});
Graph
For debugging and inspection purposes a graph in dot format may be
obtained using onGraph option:
const plugin = new ShakePlugin({
onGraph: (graph) => { ... }
});
LICENSE
This software is licensed under the MIT License.
Copyright Fedor Indutny, 2017.
Permission is hereby granted, free of charge, to any person obtaining a
copy of this software and associated documentation files (the
"Software"), to deal in the Software without restriction, including
without limitation the rights to use, copy, modify, merge, publish,
distribute, sublicense, and/or sell copies of the Software, and to permit
persons to whom the Software is furnished to do so, subject to the
following conditions:
The above copyright notice and this permission notice shall be included
in all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
USE OR OTHER DEALINGS IN THE SOFTWARE.