move config into single file, add errors to help people migrate

test/app/webpack.config.js

@@ -0,0 +1,77 @@
+const webpack = require('webpack');
+const config = require('../../config/webpack.js');
+const sapper_pkg = require('../../package.json');
+
+const mode = process.env.NODE_ENV;
+const isDev = mode === 'development';
+
+module.exports = {
+	client: {
+		entry: config.client.entry(),
+		output: config.client.output(),
+		resolve: {
+			extensions: ['.js', '.html']
+		},
+		module: {
+			rules: [
+				{
+					test: /\.html$/,
+					exclude: /node_modules/,
+					use: {
+						loader: 'svelte-loader',
+						options: {
+							hydratable: true,
+							cascade: false,
+							store: true
+						}
+					}
+				}
+			]
+		},
+		mode,
+		plugins: [
+			isDev && new webpack.HotModuleReplacementPlugin()
+		].filter(Boolean),
+		devtool: isDev && 'inline-source-map'
+	},
+
+	server: {
+		entry: config.server.entry(),
+		output: config.server.output(),
+		target: 'node',
+		resolve: {
+			extensions: ['.js', '.html']
+		},
+		externals: [].concat(
+			Object.keys(sapper_pkg.dependencies),
+			Object.keys(sapper_pkg.devDependencies)
+		),
+		module: {
+			rules: [
+				{
+					test: /\.html$/,
+					exclude: /node_modules/,
+					use: {
+						loader: 'svelte-loader',
+						options: {
+							css: false,
+							cascade: false,
+							store: true,
+							generate: 'ssr'
+						}
+					}
+				}
+			]
+		},
+		mode,
+		performance: {
+			hints: false // it doesn't matter if server.js is large
+		}
+	},
+
+	serviceworker: {
+		entry: config.serviceworker.entry(),
+		output: config.serviceworker.output(),
+		mode
+	}
+};