title: WEBPACK 4 SplitChunksPlugin doesntsplit
body: <p>i set </p>
  
  <p>```</p>
  
  <pre><code>optimization:{
  splitChunks: 
      'my-bundle1':{
            chunks:"async",
  test: (module)=&gt;{
  return  /my-bundle1/.test(module.resource)
  },
  name:"my-bundle1",
  enforce:true,
  reuseExistingChunk:true
  
  }}
  </code></pre>
  
  <p>```</p>
  
  <p>however, the source of the files with paths containing my-bundle1 does NOT appear in my-bundle1.bundle.js. rather they appear in common.js</p>
  
  <p>PS: in webpack 3 I used to create these bundles by a list of commonsChunkPlugins:
  <code>
  new CommonsChunkPlugin({
  "minChunks":function(module,count) {
  return module.resource &amp; /my-bundle1//.test(module.resource) &amp;&amp; count&gt;=2; 
  },
  "async":"mybundle1-1.0.0"
  }),
  ...
  </code></p>