Ensure it's only run once (#8)

Author: lukehorvat

fixture/child-compiler-plugin.js

@@ -0,0 +1,10 @@
+'use strict';
+
+module.exports = class ChildCompilerPlugin {
+	apply(compiler) {
+		compiler.hooks.make.tapAsync('ChildCompilerPlugin', (compilation, callback) => {
+			const childCompiler = compilation.createChildCompiler('ChildCompilerPlugin');
+			childCompiler.runAsChild(callback);
+		});
+	}
+};

fixture/webpack.config.js

@@ -1,5 +1,6 @@
 'use strict';
 const AddAssetPlugin = require('..');
+const ChildCompilerPlugin = require('./child-compiler-plugin');
 
 module.exports = {
 	output: {
@@ -9,6 +10,7 @@ module.exports = {
 	plugins: [
 		new AddAssetPlugin('rainbow.js', 'console.log("🌈")'),
 		new AddAssetPlugin('cake.js', () => 'console.log("🎂")'),
-		new AddAssetPlugin('cat.js', () => Promise.resolve('console.log("🐈")'))
+		new AddAssetPlugin('cat.js', () => Promise.resolve('console.log("🐈")')),
+		new ChildCompilerPlugin()
 	]
 };

index.js

@@ -13,7 +13,7 @@ module.exports = class AddAssetPlugin {
 	}
 
 	apply(compiler) {
-		compiler.hooks.compilation.tap('AddAssetPlugin', compilation => {
+		compiler.hooks.thisCompilation.tap('AddAssetPlugin', compilation => {
 			compilation.hooks.processAssets.tapPromise(tapOptions, async () => {
 				let source;
 				if (typeof this.source === 'string') {

test.js

@@ -9,7 +9,8 @@ test('main', async t => {
 	const config = require('./fixture/webpack.config');
 	const cwd = tempy.directory();
 	config.output.path = cwd;
-	await pify(webpack)(config);
+	const stats = await pify(webpack)(config);
+	t.false(stats.hasErrors());
 	t.true(fs.readFileSync(path.join(cwd, 'unicorn.js'), 'utf8').includes('🦄'));
 	t.true(fs.readFileSync(path.join(cwd, 'rainbow.js'), 'utf8').includes('🌈'));
 	t.true(fs.readFileSync(path.join(cwd, 'cake.js'), 'utf8').includes('🎂'));