Passing a plain function as a plugin is ignored silently

[vjpr]

🐛 Bug Report

Plugins must be paths. If they are functions they are just ignored silently.

Have you read the Contributing Guidelines on issues?

Yes.

To Reproduce

plugins.push(customWebpackPlugin)

function customWebpackPlugin(context, options) {
  console.log('hi')
  return {
    name: 'custom-webpack-plugin',
    configureWebpack(config, isServer, utils) {
		return {}
    },
  }
}

Expected behavior

hi should be printed or a warning shown.

Actual Behavior

Its not, and there is no warning.

Your Environment

• Docusaurus version used: 2.0.0-alpha.69
• Environment name and version (e.g. Chrome 78.0.3904.108, Node.js 10.17.0):
• Operating system and version (desktop or mobile):

Reproducible Demo

(Paste the link to an example repo, including a siteConfig.js, and exact instructions to reproduce the issue.)

[9oelM]

Well I'm not sure if it is something to be validated, but if it needs to be, I guess some improvement could be done at

docusaurus/packages/docusaurus/src/server/plugins/init.ts

Lines 54 to 61 in ad31fac

	if (typeof pluginItem === 'string') {
	pluginModuleImport = pluginItem;
	} else if (Array.isArray(pluginItem)) {
	[pluginModuleImport, pluginOptions = {}] = pluginItem;
	}
	if (!pluginModuleImport) {
	return null;

because this is where Docusaurus initializes plugins. Any thoughts?

[slorber]

Agree, that would be more convenient to create a local site plugin.

@9oelM yes that looks like the correct location, probably just need to test if the plugin item is a function and in such case avoid calling require() on it

[slorber]

Also, instead of silently ignoring things, it would be better to fail fast and throw an explicit error

[9oelM]

I'll be able to work on this too

[slorber]

Let's keep it open because what we want is this:

function MyPlugin() {
  return {name: "my-plugin"}
}

module.exports {
  plugins: [
    MyPlugin,
   [MyPlugin,{}],
  ],
}