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1## Circular Dependency Plugin
2
3Detect modules with circular dependencies when bundling with webpack.
4
5Circular dependencies are often a necessity in complex software, the presence of a circular dependency doesn't always imply a bug, but in the case where you believe a bug exists, this module may help find it.
6
7### Webpack Versions
8
9The latest major version of this plugin `5`, supports webpack `4.0.1` and greater as a peer dependency. Major version `4` of this plugin and below are intended to support webpack `3.x.x` and below as a peer dependency.
10
11### Basic Usage
12
13```js
14// webpack.config.js
15const CircularDependencyPlugin = require('circular-dependency-plugin')
16
17module.exports = {
18 entry: "./src/index",
19 plugins: [
20 new CircularDependencyPlugin({
21 // exclude detection of files based on a RegExp
22 exclude: /a\.js|node_modules/,
23 // include specific files based on a RegExp
24 include: /dir/,
25 // add errors to webpack instead of warnings
26 failOnError: true,
27 // allow import cycles that include an asyncronous import,
28 // e.g. via import(/* webpackMode: "weak" */ './file.js')
29 allowAsyncCycles: false,
30 // set the current working directory for displaying module paths
31 cwd: process.cwd(),
32 })
33 ]
34}
35```
36
37### Advanced Usage
38
39```js
40// webpack.config.js
41const CircularDependencyPlugin = require('circular-dependency-plugin')
42
43module.exports = {
44 entry: "./src/index",
45 plugins: [
46 new CircularDependencyPlugin({
47 // `onStart` is called before the cycle detection starts
48 onStart({ compilation }) {
49 console.log('start detecting webpack modules cycles');
50 },
51 // `onDetected` is called for each module that is cyclical
52 onDetected({ module: webpackModuleRecord, paths, compilation }) {
53 // `paths` will be an Array of the relative module paths that make up the cycle
54 // `module` will be the module record generated by webpack that caused the cycle
55 compilation.errors.push(new Error(paths.join(' -> ')))
56 },
57 // `onEnd` is called before the cycle detection ends
58 onEnd({ compilation }) {
59 console.log('end detecting webpack modules cycles');
60 },
61 })
62 ]
63}
64```
65
66If you have some number of cycles and want to fail if any new ones are
67introduced, you can use the life cycle methods to count and fail when the
68count is exceeded. (Note if you care about detecting a cycle being replaced by
69another, this won't catch that.)
70
71```js
72// webpack.config.js
73const CircularDependencyPlugin = require('circular-dependency-plugin')
74
75const MAX_CYCLES = 5;
76let numCyclesDetected = 0;
77
78module.exports = {
79 entry: "./src/index",
80 plugins: [
81 new CircularDependencyPlugin({
82 onStart({ compilation }) {
83 numCyclesDetected = 0;
84 },
85 onDetected({ module: webpackModuleRecord, paths, compilation }) {
86 numCyclesDetected++;
87 compilation.warnings.push(new Error(paths.join(' -> ')))
88 },
89 onEnd({ compilation }) {
90 if (numCyclesDetected > MAX_CYCLES) {
91 compilation.errors.push(new Error(
92 `Detected ${numCyclesDetected} cycles which exceeds configured limit of ${MAX_CYCLES}`
93 ));
94 }
95 },
96 })
97 ]
98}
99```
100
101### Maintenance
102
103This module is maintained despite few changes being necessary, please open issues if you find any bugs relating to integration with webpack core.
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