From 2a206b3dd7770246db1254ca113dad8ba22c29af Mon Sep 17 00:00:00 2001
From: Vladimir Matveev <vladima@microsoft.com>
Date: Wed, 21 Sep 2016 00:02:20 -0700
Subject: [PATCH] add check if expected directory path is non-empty string

---
 src/compiler/sys.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/compiler/sys.ts b/src/compiler/sys.ts
index f930ce295f..ea858e21fb 100644
--- a/src/compiler/sys.ts
+++ b/src/compiler/sys.ts
@@ -611,7 +611,7 @@ namespace ts {
             const originalWriteFile = sys.writeFile;
             sys.writeFile = function(path, data, writeBom) {
                 const directoryPath = getDirectoryPath(normalizeSlashes(path));
-                if (!sys.directoryExists(directoryPath)) {
+                if (directoryPath && !sys.directoryExists(directoryPath)) {
                     recursiveCreateDirectory(directoryPath, sys);
                 }
                 originalWriteFile.call(sys, path, data, writeBom);