exposed utility function to prompt for installation of missing packages

Author: FND

lib/index.js

@@ -2,7 +2,7 @@
 
 let AssetManager = require("./manager");
 let resolvePath = require("./util/resolve");
-let { abort, repr } = require("./util");
+let { loadExtension, abort, repr } = require("./util");
 let browserslist = require("browserslist");
 let SerializedRunner = require("./util/runner");
 
@@ -47,7 +47,7 @@ module.exports = (referenceDir, config, { watch, fingerprint, sourcemaps, compac
 
 		let { bucket, plugin } = plugins[type];
 		if(!plugin.call) {
-			plugin = load(plugin);
+			plugin = loadExtension(plugin, "ERROR: missing plugin");
 		}
 		let build = plugin(pluginConfig, assetManager,
 				{ browsers, sourcemaps, compact });
@@ -96,14 +96,3 @@ function makeWatcher(watchDirs, referenceDir) {
 	});
 	return watcher;
 }
-
-function load(pkg) {
-	try {
-		return require(pkg);
-	} catch(err) {
-		if(err.code !== "MODULE_NOT_FOUND") {
-			throw err;
-		}
-		abort(`ERROR: missing plugin - please install ${repr(pkg)}`);
-	}
-}

lib/util/index.js

@@ -3,9 +3,20 @@
 let path = require("path");
 let crypto = require("crypto");
 
-exports.abort = (msg, code = 1) => {
-	console.error(msg);
-	process.exit(code);
+exports.abort = abort;
+exports.repr = repr;
+
+// attempts to `require` a module, prompting the user to install the
+// corresponding package if it is unavailable
+exports.loadExtension = (pkg, errorMessage, supplier = pkg) => {
+	try {
+		return require(pkg);
+	} catch(err) {
+		if(err.code !== "MODULE_NOT_FOUND") {
+			throw err;
+		}
+		abort(`${errorMessage} - please install ${repr(supplier)}`);
+	}
 };
 
 exports.generateFingerprint = (filepath, data) => {
@@ -30,12 +41,17 @@ exports.promisify = fn => {
 	});
 };
 
-exports.repr = (value, jsonify = true) => {
+function abort(msg, code = 1) {
+	console.error(msg);
+	process.exit(code);
+}
+
+function repr(value, jsonify = true) {
 	if(jsonify) {
 		value = JSON.stringify(value);
 	}
 	return `\`${value}\``;
-};
+}
 
 function generateHash(str) {
 	let hash = crypto.createHash("md5");