Allow preset to nullify theme-provided components overriden by preset plugins

[reutenkoivan]

Have you read the Contributing Guidelines on issues?

• I have read the Contributing Guidelines on issues.

Prerequisites

• I'm using the latest version of Docusaurus.
• I have tried the npm run clear or yarn clear command.
• I have tried rm -rf node_modules yarn.lock package-lock.json and re-installing packages.
• I have tried creating a repro with https://new.docusaurus.io.
• I have read the console error message carefully (if applicable).

Description

If you are using "theme" parameter instead of "preset" it's not possible to include custom UI components registered by "getThemePath" method from plugins.

Steps to reproduce

1. clone this repository
2. cd website
3. yarn
4. yarn build
5. yarn serve
6. open http://localhost:3000/
7. You don't see search input

Expected behavior

1. go to <root>/website/node_modules/@docusaurus/core/lib/server/index.js
2. change return from loadPluginConfigs to

return [
        ...presetThemes,
        ...presetPlugins,
        ...standaloneThemes,
        ...standalonePlugins,
    ]

3. yarn build
4. yarn serve
5. now you can see search input

Actual behavior

it happening because in this line alias from plugin overriding by alias from theme-classic.

// themePaths ==== [
//   '@docusaurus/core/lib/client/theme-fallback',
//   '@easyops-cn/docusaurus-search-local/dist/client/client/theme',
//   '@docusaurus/theme-classic/lib-next/theme'
// ]

// returns from "loadThemeAliases"
// {
// --- other aliases---
//   '@theme/SearchBar/EmptyTemplate': '@easyops-cn/docusaurus-search-local/dist/client/client/theme/SearchBar/EmptyTemplate.js',
//   '@theme/SearchBar/SearchBar': '@easyops-cn/docusaurus-search-local/dist/client/client/theme/SearchBar/SearchBar.jsx',
//   '@theme/SearchBar/SuggestionTemplate': '@easyops-cn/docusaurus-search-local/dist/client/client/theme/SearchBar/SuggestionTemplate.js',
//   '@theme/SearchBar/__mocks__/icons': '@easyops-cn/docusaurus-search-local/dist/client/client/theme/SearchBar/__mocks__/icons.js',
//   '@theme/SearchBar/fetchIndexes': '@easyops-cn/docusaurus-search-local/dist/client/client/theme/SearchBar/fetchIndexes.js',
//   '@theme/SearchBar/icons': '@easyops-cn/docusaurus-search-local/dist/client/client/theme/SearchBar/icons.js',
//   '@theme/SearchBar': '@docusaurus/theme-classic/lib-next/theme/SearchBar.js',  <--- Wrong alias
// --- other aliases---
// }

Your environment

• Public source code:
• Public site URL:
• Docusaurus version used: 2.0.0-beta.15
• Environment name and version (e.g. Chrome 89, Node.js 16.4):
• Operating system and version (e.g. Ubuntu 20.04.2 LTS):

Reproducible demo

No response

Self-service

• I'd be willing to fix this bug myself.

[Josh-Cena]

Hey, this is surprising, but working as intended. We want plugin default themes to be overridable by external themes, so the best we can do is always give themes a higher precedence than plugins. If you want to provide themes in your plugin, don't bundle it in your preset with a theme you are trying to override.

I do think something can be done here, for example, the ability for a preset to nullify part of the theme a plugin provides—but of course, we will not tweak the theme loading order. This has already been documented/specced.

[slorber]

@weareoutman I suggest you present your Docusaurus search plugin as a theme instead of a plugin.

We have docusaurus-theme-search-algolia, and your plugin is similar so it would be better to do the same.

There are not a lot of differences between themes and plugins apart this aliasing ordering.

@reutenkoivan this should work:

  plugins: [
    [
      '@docusaurus/plugin-content-docs',
      {
        path: path.join(__dirname, 'docs'),
        routeBasePath: '/'
      },
    ],
  ],
  themes: [
    ['@docusaurus/theme-classic', {customCss: [require.resolve('./src/css/custom.css')]}],
    '@easyops-cn/docusaurus-search-local',
  ],

[weareoutman]

@slorber Thanks and I just updated our docs about using it as a theme.

[slorber]

Thanks 👍 I guess we can close now, unless someone reports another use-case

[kaushal0107]

@weareoutman Thanks for the Theme.
I configured it on my Docusaurus setup from https://github.com/easyops-cn/docusaurus-search-local .
But after Building I'm getting following error.
search-index.json not found
there is no such thing mentioned in the steps.
Please guide.