Plugin apply not working for multi compiler

[nuintun]

Bug report

What is the current behavior?

Plugin apply not working for multi compiler.

If the current behavior is a bug, please provide the steps to reproduce.

import webpack from 'webpack';

const compiler = webpack([{
  // ...
}]);

for(const compiler of compiler.compilers) {
  // DefinePlugin
  new webpack.DefinePlugin(
    // ...
  ).apply(compiler);

  // EntryPlugin
  new webpack.EntryPlugin(
    // ...
  ).apply(compiler);

  // HotModuleReplacementPlugin
  new webpack.HotModuleReplacementPlugin(
    // ...
  ).apply(compiler);
}

All plugins DefinePlugin, EntryPlugin, HotModuleReplacementPlugin are not working.

Also see: https://github.com/webpack/webpack-dev-server/blob/edbc6e14cd96c6d652f8fef2d5fcfe6af829231a/lib/Server.js#L1639

What is the expected behavior?

Plugin apply not working for multi compiler.

Other relevant information:
webpack version: 5.91.0
Node.js version: 21.7.1
Operating System: Windows 11
Additional tools: N/A

[nuintun]

This issues is very strange.

See: https://github.com/nuintun/webpack-dev-service/blob/63ef2873b654ad5a4473cd80a903a12bc605f493/src/server/index.ts#L47-L48

It's work fine.

const hotMiddleware = hot(compiler, hotOptions);
const devMiddleware = dev(compiler, options);

It's not work for multi compiler, but single compiler is ok.

const devMiddleware = dev(compiler, options);
const hotMiddleware = hot(compiler, hotOptions);

The dev module just a dev middleware for koa2 like webpack-dev-middleware.

[nuintun]

Resolved, dev start the watching, but plugins must be initialized before watching!