fix: ignore empty strings in an array

lib/watchpack.js

@@ -23,24 +23,28 @@ function addWatchersToSet(watchers, set) {
 }
 
 const stringToRegexp = ignored => {
+	if (ignored.length === 0) {
+		return;
+	}
 	const source = globToRegExp(ignored, { globstar: true, extended: true })
 		.source;
-	const matchingStart = source.slice(0, source.length - 1) + "(?:$|\\/)";
-	return matchingStart;
+	return source.slice(0, source.length - 1) + "(?:$|\\/)";
 };
 
 const ignoredToFunction = ignored => {
 	if (Array.isArray(ignored)) {
-		if (ignored.length === 0) {
+		const stringRegexps = ignored.map(i => stringToRegexp(i)).filter(Boolean);
+		if (stringRegexps.length === 0) {
 			return () => false;
 		}
-		const regexp = new RegExp(ignored.map(i => stringToRegexp(i)).join("|"));
+		const regexp = new RegExp(stringRegexps.join("|"));
 		return x => regexp.test(x.replace(/\\/g, "/"));
 	} else if (typeof ignored === "string") {
-		if (ignored.length === 0) {
+		const stringRegexp = stringToRegexp(ignored);
+		if (!stringRegexp) {
 			return () => false;
 		}
-		const regexp = new RegExp(stringToRegexp(ignored));
+		const regexp = new RegExp(stringRegexp);
 		return x => regexp.test(x.replace(/\\/g, "/"));
 	} else if (ignored instanceof RegExp) {
 		return x => ignored.test(x.replace(/\\/g, "/"));

test/Watchpack.js

@@ -291,6 +291,28 @@ describe("Watchpack", function() {
 		});
 	});
 
+	it("should watch a file when ignore is an array with empty string", function(done) {
+		var w = new Watchpack({
+			aggregateTimeout: 1000,
+			ignored: ["", ""]
+		});
+		var changeEvents = 0;
+		w.on("change", function(file) {
+			file.should.be.eql(path.join(fixtures, "a"));
+			changeEvents++;
+		});
+		w.on("aggregated", function(changes) {
+			Array.from(changes).should.be.eql([path.join(fixtures, "a")]);
+			changeEvents.should.be.greaterThan(0);
+			w.close();
+			done();
+		});
+		w.watch([path.join(fixtures, "a")], []);
+		testHelper.tick(function() {
+			testHelper.file("a");
+		});
+	});
+
 	it("should watch a file when ignore is empty string", function(done) {
 		var w = new Watchpack({
 			aggregateTimeout: 1000,