Merging complete webpack configs using mergeWithRules empties primitive arrays

[dennisoelkers]

I am in the process of upgrading to v4, currently trying to replace former usages of merge.smart to merge complete webpack configurations. My current definition using mergeWithRules looks like this:

mergeWithRules({
  module: {
    rules: {
      test: "match",
      use: {
        loader: "match",
        options: "replace"
      }
    }
  },
  resolve: {
    extensions: 'append',
    module: 'match',
    alias: 'match'
  },
  resolveLoader: {
    modules: "match",
    moduleExtensions: "match"
  }
})

There are two issues I am currently having:

1. When merging two configs, I need to define rules for e.g. resolve.extensions, otherwise I am getting an error
2. Defining a rule like above for keys which would otherwise result in an error, lead to resolve.extensions (which contains an array of strings) being an empty array in the resulting config.

Am I doing something wrong? How can I merge two complete webpack configurations while still replacing redundant loaders and merging arrays for uniqueness like resolve.extensions?

[bebraw]

Can you provide a full example of the configuration you are trying to merge as above? Ideally this should be something I can run and convert as a test. It's possible mergeWithRules is still missing some corner cases as it's a new API so this step will let me validate that.

In my personal work, I always use regular merge and compose from small fragments but I understand if that's not always possible.

[dennisoelkers]

A simple example would be this:

const module = {
    rules: {
      test: "match",
      use: {
        loader: "match",
        options: "replace",
      },
    },
  };
const _mergeWithoutRule = mergeWithRules({
  module,
});

const _mergeWithExplicitRule = mergeWithRules({
  module,
  resolve: {
    extensions: 'append',
    module: 'match',
    alias: 'match',
  },
});

const config = { resolve: { extensions: ['.js'] } };

expect(() => _mergeWithoutRule(config, config)).not.toThrow();
expect(_mergeWithExplicitRule(config, config)).toEqual(config);

This leaves out all the handling of the module part, which is fine. It merges a config back to itself, which is not really helpful, but works to produce the error/invalid result.

I also added runkit links for easier reproducibility:

• throwing an error without explicit rules: https://runkit.com/embed/opx1fiz5rj4a
• not merging string arrays: https://runkit.com/embed/rmvj4mu8zdag

[bebraw]

Ok, thanks! I'll work against your examples then.

[bebraw]

I've fixed the throwing part at 5.4.0 and I have a proposal for the rest at #152.

[dennisoelkers]

Great, thanks for that! I will try it out and check if it fixes our issue asap.