TypeError: Cannot read property '0' of undefined

[andreventuravale]

Using latest version of master it throws a exception at registration[0] expression:

Head is: 243543c7a3eb4e54f5be1df4eab54c749d7f7f7e

Process args: 0:"/Users/andrevale/.nvm/versions/node/v8.9.1/bin/node" 1:"{project}/server/index.js" 2:"--color"

exports.tap = (tapable, name, reason, callback) => {
  if (tapable.hooks) {
    tapable.hooks[name].tap(reason, callback);
  } else {
    if (!tapable.__hardSource_hooks || !tapable.__hardSource_hooks[name]) {
      const registration =
        knownPluginRegistrations[tapable.constructor.name][name];
      exports.register(tapable, name, >>> registration[0] <<<, registration[1]);

Exception has occurred: TypeError
TypeError: Cannot read property '0' of undefined
    at Object.exports.tap (.../hard-source-webpack-plugin/lib/util/plugin-compat.js:118:51)
    at SupportMiniCssExtractPlugin.apply (.../hard-source-webpack-plugin/lib/SupportMiniCssExtractPlugin.js:7:18)
    at HardSourceWebpackPlugin.apply (.../hard-source-webpack-plugin/index.js:460:41)
    at Compiler.apply (.../.../node_modules/tapable/lib/Tapable.js:375:16)
    at webpack (.../.../node_modules/webpack/lib/webpack.js:33:19)
    at Promise (.../.../node_modules/.../lib/file.js:34:28)
    at new Promise (<anonymous>)
    at Server.hmr (.../.../node_modules/.../lib/file.js:30:10)
    at Server.start (.../.../node_modules/.../index.js:100:43)
    at start (.../.../server/index.js:719:10)
    at module.exports (.../.../node_modules/throng/lib/throng.js:6:32)
    at Object.<anonymous> (.../.../server/index.js:722:1)
    at Module._compile (module.js:635:30)
    at Object.Module._extensions..js (module.js:646:10)
    at Module.load (module.js:554:32)
    at tryModuleLoad (module.js:497:12)
    at Function.Module._load (module.js:489:3)
    at Function.Module.runMain (module.js:676:10)
    at startup (bootstrap_node.js:187:16)
    at bootstrap_node.js:608:3

"webpack": "3.12.0",

[mzgoddard]

@andreventuravale Your installed project dependencies are ... odd? MiniCss is enabled for webpack 4 based on discovering a part of webpack that only exists in webpack 4. Can you describe your project dependency folder layout so I can help figure this out or support it?

Fixing this may be deleting your node_modules directory and any npm/yarn cache and installing fresh.

[sorrycc]

I also encountered the same problem because I have both webpack@3 and webpack@4 in different node_modules deps, and the webpackFeatures.generator is set to true. After removing webpack@4, it works. I think this way of judging webpackFeatures should be improved.