Add possibility to define configuration with customPreprocessors

[mjeanroy]

Hi @jlmakes ,

Currently, the only way to specify rollup configuration is with the rollupPreprocessor: easy, and enough for 99% use case.

But, it could be great to support configuration using customPreprocessors (documented here, or you can see it implemented by karma-babel-preprocessor).

It could be a simple solution to provide different rollup configuration for specific files, for example:

module.exports = (config) => {
  config.set({
    // Karma Configuration
    // ...

    preprocessors: {
      'test/index1.js': ['rollup'],
      'test/index2.js': ['rollupCustom'],
    },

    rollupPreprocessor: {
      // Default rollup configuration...
    },

    customPreprocessors: {
      rollupCustom: {
        base: 'rollup',
        // Custom rollup configuration for this file...
      },
    },
  });
});

I already made some tests on a project and I would be happy to open a PR for that, what do you think?

[jlmakes]

Thanks @mjeanroy I appreciate the contribution!
Next change I get, I’ll merge and prepare a new release.

[mjeanroy]

Ok, thank you!

Please let me know when you do, this feature will make my life easier 😉

[jlmakes]

Yeaah buddy, this is now in version 4.0.0 @mjeanroy