Feature motivation

Right now, the way the plugin's hook system and webpack multi-compiler works, it makes it quite difficult to actually get the plugin hooks. For example, let's say we have

const ForkTsCheckerPlugin = require('fork-ts-checker-webpack-plugin');
const compiler = webpack([
	// array of webpack configuration with fork-ts-checker plugin
]);
const pluginHooks = ForkTsCheckerPlugin.getCompilerHooks(compiler);

// This won't work, because ForkTsCheckerPlugin didn't attach itself to
// the multi-compiler, rather the individual compilers
pluginHooks.receive.tap((d, l) => {
	console.log('done');
});

In such multi-compiler setup, we can not hook into fork-ts-checker hooks from the multi-compiler instance.

Feature description

However, we can loop over compilers property to get the actual compiler where the plugin is attached.

compiler.compilers.forEach(singleCompiler => {
	const pluginHooks = ForkTsCheckerPlugin.getCompilerHooks(singleCompiler);

	// This will work
	pluginHooks.receive.tap((d, l) => {
		console.log('done');
	});
});

Feature implementation

So I was thinking maybe the ForkTsCheckerPlugin.getCompilerHooks could be a bit intuitive to support multi-compiler out of the box. Internal implementation could be like this

1. If compiler is a single instance, the don't change anything.
2. If compiler is a multi-compiler instance, then loop over all compilers instance and add the callback on the same hook for every instance.

Maybe this would be a bit out of scope, but I think and helper would be really nice here. Something like

export function getMultiCompilerHooks(compiler) {
	if (! 'compilers' in compiler) {
		throw new Error('Works only with multi-compiler instance');
	}
	const hooks = [];
	compiler.compilers.forEach(singleCompiler => {
		hooks.push(getCompilerHooks(singleCompiler);
	});
	return hooks;
}

In any case, a little documentation on usage of the hooks would be really nice. I was trying to implement async typechecking and custom error reporting for a multi-compiler friendly webpack setup on my tooling and I really needed to dig through the source code to findout how and why things work.