allow merging of yaml, toml, js config

[neumayr]

Summary

allows the merging of yaml, toml and js config

My Team manages eg. themeConfig.nav in config.yml for readability and ease of use. However some advanced js syntax can’t be managed by yaml like extendMarkdown: md => {md.use(…)}.
I would like to have two configuration files. config.yml and config.js work side by side.
One for simple theme config and the js for advanced configuration.

My Setup simplified

In the config.yml contains the config basic documentation authors can edit. The config.js contains advanced configuration for markdown and plugins a basic author better don't touch 😉

---
# .vuepress/config.yml
title: '📝 My Awesome Documentation'
description: "Awesome Docs"
port: 4000

// .vuepress/config.js
module.exports = {
  plugins: [
    ['@vuepress/search', { searchMaxSuggestions: 10 }],
    '@vuepress/last-updated'
  ],
  markdown: {
    lineNumbers: true,
    toc: {
      includeLevel: [2, 3, 4]
    },
    extendMarkdown: md => {
      md.use(require('markdown-it-mermaid').default)
    }
  }
}

🔗 #804

What kind of change does this PR introduce? (check at least one)

• Bugfix
• Feature
• Code style update
• Refactor
• Docs
• Build-related changes
• Other, please describe:

If changing the UI of default theme, please provide the before/after screenshot:

Does this PR introduce a breaking change? (check one)

• Yes
• No

If yes, please describe the impact and migration path for existing applications:

The PR fulfills these requirements:

• When resolving a specific issue, it's referenced in the PR's title (e.g. fix #xxx[,#xxx], where "xxx" is the issue number)

You have tested in the following browsers: (Providing a detailed version will be better.)

• Chrome
• Firefox
• Safari
• Edge
• IE

If adding a new feature, the PR's description includes:

• A convincing reason for adding this feature
• Related documents have been updated
• Related tests have been updated

To avoid wasting your time, it's best to open a feature request issue first and wait for approval before working on it.

Other information:
From reading the docs I assume module.export is an object. Is this fact correct? If not, I would need help on how to elegant require an object or function.

/cc @ekoeryanto

[ulivz]

This merge is unreasonable and will cause issues, because the config of vuepress allows users to export a function.

Thus, I think that you should do this merge in your config.js.

[ulivz]

Why removing it?

[neumayr]

Sorry, I've tested several scenarios and looked at the netlify build and output. I did't wanted to change the vuepress config. I've awaited some constructive feedback, this is why I've asked this in the description.

Other information:
From reading the docs I assume module.export is an object. Is this fact correct? If not, I would need help on how to elegant require an object or function.

[ulivz]

I think that you should emphasize that this is only "Shadow Merge".

[neumayr]

This merge is unreasonable and will cause issues, because the config of vuepress allows users to export a function.

Thank you, important information.
Is there an elegant way to check for a function and get this working?

Thus, I think that you should do this merge in your config.js.

Probably, but because other folks found this useful too I would try to get this working out of the box. @ulivz, you're a vuepress and js professional. Myself aren't. Share your knowledge ✌️