From 1fd47f2517682d26d39bf0d105a96ef4ce6d7f35 Mon Sep 17 00:00:00 2001
From: Valera Rozuvan <valera.rozuvan@gmail.com>
Date: Fri, 28 Sep 2018 18:08:11 +0300
Subject: [PATCH 1/2] Fix GH#18217 issue for FileLog.

---
 src/typingsInstaller/nodeTypingsInstaller.ts | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/src/typingsInstaller/nodeTypingsInstaller.ts b/src/typingsInstaller/nodeTypingsInstaller.ts
index 00ee8b4fa1923..5b68a20765e49 100644
--- a/src/typingsInstaller/nodeTypingsInstaller.ts
+++ b/src/typingsInstaller/nodeTypingsInstaller.ts
@@ -1,5 +1,3 @@
-// tslint:disable no-unnecessary-type-assertion (TODO: tslint can't find node types)
-
 namespace ts.server.typingsInstaller {
     const fs: {
         appendFileSync(file: string, content: string): void
@@ -13,15 +11,25 @@ namespace ts.server.typingsInstaller {
 
     class FileLog implements Log {
         private logEnabled = true;
-        constructor(private readonly logFile?: string) {
+        private readonly logFile: string = "";
+
+        constructor(logFile: string | undefined) {
+            if (typeof logFile !== "string") {
+                this.logEnabled = false;
+            }
+            else {
+                this.logFile = logFile;
+            }
         }
 
         isEnabled = () => {
-            return this.logEnabled && this.logFile !== undefined;
+            return this.logEnabled;
         }
         writeLine = (text: string) => {
+            if (!this.logEnabled) return;
+
             try {
-                fs.appendFileSync(this.logFile!, `[${nowString()}] ${text}${sys.newLine}`); // TODO: GH#18217
+                fs.appendFileSync(this.logFile, `[${nowString()}] ${text}${sys.newLine}`);
             }
             catch (e) {
                 this.logEnabled = false;

From 397364ce5a9f2f719d9a804a0ee9eb2e9c0c99ab Mon Sep 17 00:00:00 2001
From: Valera Rozuvan <valera.rozuvan@gmail.com>
Date: Tue, 2 Oct 2018 12:11:03 +0300
Subject: [PATCH 2/2] Refactor FileLog class to not use isEnabled property.

---
 src/typingsInstaller/nodeTypingsInstaller.ts | 17 ++++-------------
 1 file changed, 4 insertions(+), 13 deletions(-)

diff --git a/src/typingsInstaller/nodeTypingsInstaller.ts b/src/typingsInstaller/nodeTypingsInstaller.ts
index 5b68a20765e49..62bdcfce2603b 100644
--- a/src/typingsInstaller/nodeTypingsInstaller.ts
+++ b/src/typingsInstaller/nodeTypingsInstaller.ts
@@ -10,29 +10,20 @@ namespace ts.server.typingsInstaller {
     } = require("path");
 
     class FileLog implements Log {
-        private logEnabled = true;
-        private readonly logFile: string = "";
-
-        constructor(logFile: string | undefined) {
-            if (typeof logFile !== "string") {
-                this.logEnabled = false;
-            }
-            else {
-                this.logFile = logFile;
-            }
+        constructor(private logFile: string | undefined) {
         }
 
         isEnabled = () => {
-            return this.logEnabled;
+            return typeof this.logFile === "string";
         }
         writeLine = (text: string) => {
-            if (!this.logEnabled) return;
+            if (typeof this.logFile !== "string") return;
 
             try {
                 fs.appendFileSync(this.logFile, `[${nowString()}] ${text}${sys.newLine}`);
             }
             catch (e) {
-                this.logEnabled = false;
+                this.logFile = undefined;
             }
         }
     }