Add an exists and existsSync method.

Sometimes you'd rather prefer not having an error thrown (à la `.stat`). Because both functions share the code for fetching the internal file object, it has been refactored out into a common function called `meta`.

Specs updated to match.

Author: izaakschroeder

lib/MemoryFileSystem.js

@@ -39,15 +39,24 @@ function pathToArray(path) {
 function trueFn() { return true; }
 function falseFn() { return false; }
 
-MemoryFileSystem.prototype.statSync = function(_path) {
+MemoryFileSystem.prototype.meta = function(_path) {
 	var path = pathToArray(_path);
 	var current = this.data;
 	for(var i = 0; i < path.length - 1; i++) {
 		if(!isDir(current[path[i]]))
-			throw new Error("Path doesn't exist '" + _path + "'");
+			return null;
 		current = current[path[i]];
 	}
-	if(_path === "/" || isDir(current[path[i]])) {
+	return current[path[i]];
+}
+
+MemoryFileSystem.prototype.existsSync = function(_path) {
+	return !!this.meta(_path);
+}
+
+MemoryFileSystem.prototype.statSync = function(_path) {
+	var current = this.meta(_path);
+	if(_path === "/" || isDir(current)) {
 		return {
 			isFile: falseFn,
 			isDirectory: trueFn,
@@ -57,7 +66,7 @@ MemoryFileSystem.prototype.statSync = function(_path) {
 			isFIFO: falseFn,
 			isSocket: falseFn
 		};
-	} else if(isFile(current[path[i]])) {
+	} else if(isFile(current)) {
 		return {
 			isFile: trueFn,
 			isDirectory: falseFn,
@@ -187,7 +196,7 @@ MemoryFileSystem.prototype.normalize = normalize;
 
 // async functions
 
-["stat", "readdir", "mkdirp", "mkdir", "rmdir", "unlink", "readlink"].forEach(function(fn) {
+["exists", "stat", "readdir", "mkdirp", "mkdir", "rmdir", "unlink", "readlink"].forEach(function(fn) {
 	MemoryFileSystem.prototype[fn] = function(path, callback) {
 		try {
 			var result = this[fn + "Sync"](path);

test/MemoryFileSystem.js

@@ -28,11 +28,13 @@ describe("directory", function() {
 		fs.readdirSync("//test").should.be.eql(["sub2"]);
 		fs.rmdirSync("/test/sub2");
 		fs.rmdirSync("/test");
+		fs.existsSync("/test").should.be.eql(false);
 		(function() {
 			fs.readdirSync("/test");
 		}).should.throw();
 		fs.readdirSync("/").should.be.eql(["root\\dir"]);
 		fs.mkdirpSync("/a/depth/sub/dir");
+		fs.existsSync("/a/depth/sub").should.be.eql(true);
 		var stat = fs.statSync("/a/depth/sub");
 		stat.isFile().should.be.eql(false);
 		stat.isDirectory().should.be.eql(true);
@@ -50,11 +52,13 @@ describe("directory", function() {
 		fs.readdirSync("C:\\\\test").should.be.eql(["sub2"]);
 		fs.rmdirSync("C:\\test\\sub2");
 		fs.rmdirSync("C:\\test");
+		fs.existsSync("C:\\test").should.be.eql(false);
 		(function() {
 			fs.readdirSync("C:\\test");
 		}).should.throw();
 		fs.readdirSync("C:").should.be.eql(["root-dir"]);
 		fs.mkdirpSync("D:\\a\\depth\\sub\\dir");
+		fs.existsSync("D:\\a\\depth\\sub").should.be.eql(true);
 		var stat = fs.statSync("D:\\a\\depth\\sub");
 		stat.isFile().should.be.eql(false);
 		stat.isDirectory().should.be.eql(true);
@@ -359,4 +363,4 @@ describe("os", function() {
 			fileSystem.statSync("C:\\a/dir\\index").isFile().should.be.eql(true);
 		});
 	});
-});
+});