Support other type of webpack configs

lib/core/package.json

@@ -46,6 +46,7 @@
     "find-cache-dir": "^1.0.0",
     "global": "^4.3.2",
     "html-webpack-plugin": "^3.2.0",
+    "interpret": "^1.1.0",
     "json5": "^1.0.1",
     "postcss-flexbugs-fixes": "^3.3.1",
     "postcss-loader": "^2.1.5",

lib/core/src/server/config.js

@@ -2,6 +2,7 @@
 import fs from 'fs';
 import path from 'path';
 import findCacheDir from 'find-cache-dir';
+import interpret from 'interpret';
 import { logger } from '@storybook/node-logger';
 import { createDefaultWebpackConfig } from './config/defaults/webpack.config';
 import devBabelConfig from './config/babel';
@@ -58,6 +59,87 @@ function informAboutCustomConfig(defaultConfigName) {
   logger.info(`=> Using default webpack setup based on "${defaultConfigName}".`);
 }
 
+// Copied and modified from
+// https://github.com/webpack/webpack-cli/blob/ca504de8c7c0ea66278021b72fa6a953e3ffa43c/bin/convert-argv.js#L102-L119
+function registerCompiler(moduleDescriptor) {
+  if (!moduleDescriptor) {
+    return 0;
+  }
+
+  if (typeof moduleDescriptor === 'string') {
+    require(moduleDescriptor);
+    return 1;
+  }
+
+  if (!Array.isArray(moduleDescriptor)) {
+    moduleDescriptor.register(require(moduleDescriptor.module));
+    return 1;
+  }
+
+  let registered = 0;
+
+  for (let i = 0; i < moduleDescriptor.length; i += 1) {
+    try {
+      registered += registerCompiler(moduleDescriptor[i]);
+      break;
+    } catch (e) {
+      // do nothing
+    }
+  }
+
+  return registered;
+}
+
+// Copied and modified from
+// https://github.com/webpack/webpack-cli/blob/ca504de8c7c0ea66278021b72fa6a953e3ffa43c/bin/convert-argv.js#L121-L137
+function requireConfig(configPath) {
+  const config = require(configPath);
+
+  const isES6DefaultExported =
+    typeof config === 'object' && config !== null && typeof config.default !== 'undefined';
+
+  return isES6DefaultExported ? config.default : config;
+}
+
+// Copied and modified from
+// https://github.com/webpack/webpack-cli/blob/ca504de8c7c0ea66278021b72fa6a953e3ffa43c/bin/convert-argv.js#L45-L143
+function loadCustomConfig(configDir) {
+  const extensions = Object.keys(interpret.extensions).sort((a, b) => {
+    if (a === '.js') {
+      return -1;
+    }
+    if (b === '.js') {
+      return 1;
+    }
+    return a.length - b.length;
+  });
+  const customConfigCandidates = ['webpack.config', 'webpackfile']
+    .map(filename =>
+      extensions.map(ext => ({
+        path: path.resolve(configDir, filename + ext),
+        ext,
+      }))
+    )
+    .reduce((a, i) => a.concat(i), []);
+
+  for (let i = 0; i < customConfigCandidates.length; i += 1) {
+    const customConfigPath = customConfigCandidates[i].path;
+    if (fs.existsSync(customConfigPath)) {
+      if (registerCompiler(interpret.extensions[customConfigCandidates[i].ext]) === 0) {
+        logger.warn(`=> Custom configuration file ${customConfigPath} is detected`);
+        logger.warn(`   but impossible to import loader for ${customConfigCandidates[i].ext}`);
+      }
+      try {
+        return requireConfig(customConfigPath);
+      } catch (e) {
+        return null;
+      }
+    }
+  }
+
+  return null;
+}
+
 // `baseConfig` is a webpack configuration bundled with storybook.
 // Storybook will look in the `configDir` directory
 // (inside working directory) if a config path is not provided.
@@ -86,15 +168,13 @@ export default options => {
 
   // Check whether user has a custom webpack config file and
   // return the (extended) base configuration if it's not available.
-  const customConfigPath = path.resolve(configDir, 'webpack.config.js');
+  const customConfig = loadCustomConfig(configDir);
 
-  if (!fs.existsSync(customConfigPath)) {
+  if (customConfig === null) {
     informAboutCustomConfig(defaultConfigName);
     return defaultConfig;
   }
 
-  const customConfig = require(customConfigPath);
-
   if (typeof customConfig === 'function') {
     logger.info('=> Loading custom webpack config (full-control mode).');
     return customConfig(wrapBasicConfig(config), configType, defaultConfig);

yarn.lock

@@ -8744,7 +8744,7 @@ internal-ip@1.2.0:
   dependencies:
     meow "^3.3.0"
 
-interpret@^1.0.0:
+interpret@^1.0.0, interpret@^1.1.0:
   version "1.1.0"
   resolved "https://registry.yarnpkg.com/interpret/-/interpret-1.1.0.tgz#7ed1b1410c6a0e0f78cf95d3b8440c63f78b8614"