From f39b49d756110e24ac75c81413cb13e8a0a423b0 Mon Sep 17 00:00:00 2001
From: Andrew Casey <andrew.casey@microsoft.com>
Date: Thu, 17 Oct 2019 11:36:45 -0700
Subject: [PATCH] Update another writeFile call-site

---
 src/compiler/program.ts |  2 +-
 src/compiler/sys.ts     |  2 +-
 src/compiler/watch.ts   | 15 +++++++++++++--
 3 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/src/compiler/program.ts b/src/compiler/program.ts
index 44cf374ea75..6a697b9c180 100644
--- a/src/compiler/program.ts
+++ b/src/compiler/program.ts
@@ -124,7 +124,7 @@ namespace ts {
                 try {
                     writeFileWorker(fileName, data, writeByteOrderMark);
                 }
-                catch (_) {
+                catch {
                     ensureDirectoriesExist(getDirectoryPath(normalizePath(fileName)));
                     writeFileWorker(fileName, data, writeByteOrderMark);
                 }
diff --git a/src/compiler/sys.ts b/src/compiler/sys.ts
index c85bb48bb9e..c4a5012b265 100644
--- a/src/compiler/sys.ts
+++ b/src/compiler/sys.ts
@@ -547,7 +547,7 @@ namespace ts {
             try {
                 originalWriteFile.call(sys, path, data, writeBom);
             }
-            catch (_) {
+            catch {
                 const directoryPath = getDirectoryPath(normalizeSlashes(path));
                 if (directoryPath && !sys.directoryExists(directoryPath)) {
                     recursiveCreateDirectory(directoryPath, sys);
diff --git a/src/compiler/watch.ts b/src/compiler/watch.ts
index 06871fc9cac..f6e334aa47a 100644
--- a/src/compiler/watch.ts
+++ b/src/compiler/watch.ts
@@ -307,9 +307,20 @@ namespace ts {
         function writeFile(fileName: string, text: string, writeByteOrderMark: boolean, onError: (message: string) => void) {
             try {
                 performance.mark("beforeIOWrite");
-                ensureDirectoriesExist(getDirectoryPath(normalizePath(fileName)));
 
-                host.writeFile!(fileName, text, writeByteOrderMark);
+                // PERF: Checking for directory existence is expensive.
+                // Instead, assume the directory exists and fall back
+                // to creating it if the file write fails.
+                // NOTE: If patchWriteFileEnsuringDirectory has been called,
+                // the file write will do its own directory creation and
+                // the ensureDirectoriesExist call will always be redundant.
+                try {
+                    host.writeFile!(fileName, text, writeByteOrderMark);
+                }
+                catch {
+                    ensureDirectoriesExist(getDirectoryPath(normalizePath(fileName)));
+                    host.writeFile!(fileName, text, writeByteOrderMark);
+                }
 
                 performance.mark("afterIOWrite");
                 performance.measure("I/O Write", "beforeIOWrite", "afterIOWrite");