Fix loader concatentation bug

[stefvhuynh]

This has to do with using custom webpack.config.js files. The code tries to add customConfig.module.loaders. And if customConfig.module is not defined, there is an error.

[arunoda]

I need more information. I can't see what this solves anything. This change seems to have no effect on anything.

Am I wrong?

[stefvhuynh]

If I have a custom webpack config that looks like this, it'll break:

module.exports = {
  resolves: { extensions: [".jsx"] }
}

I can fix it, by changing it to this:

module.exports = {
  resolves: { extensions: [".jsx"] },
  module: {}
}

Take a look at these lines: https://github.com/kadirahq/react-storybook/blob/master/src/server/config.js#L90-L93

If customConfig.module does not exist, it uses {}. However, on line 93, it expects customConfig.module to be defined (to access customConfig.module.loaders).

[arunoda]

Okay. I got it.
Then the PR should be something like this:

return {
    ...customConfig,
    // We'll always load our configurations after the custom config.
    // So, we'll always load the stuff we need.
    ...config,
    // We need to use our and custom plugins.
    plugins: [
      ...config.plugins,
      ...customConfig.plugins || [],
    ],
    module: {
      ...config.module,
      // We need to use our and custom loaders.
      ...customConfig.module || {},
      loaders: [
        ...config.module.loaders,
        ...customConfig.module? customConfig.module.loaders || [] : {},
      ],
    },
  };

Isn't it?

[stefvhuynh]

I think instead of {}, you want [] for the second part of the ternary. But whichever way you prefer is how I'll do it (with the ternary or by defining customConfig.module like I did).

[arunoda]

@stefvhuynh Your PR sounds great. I'll do a release within today.