From fa9f071c1480288996ad0429fd94703acfb43972 Mon Sep 17 00:00:00 2001
From: Ryan Cavanaugh <RyanCavanaugh@users.noreply.github.com>
Date: Mon, 25 Jun 2018 14:10:27 -0700
Subject: [PATCH] Don't try to write --pretty results to unsupported consoles
 in --build

---
 src/tsc/tsc.ts | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/src/tsc/tsc.ts b/src/tsc/tsc.ts
index 47d2c0b5c74..97e239c8bca 100644
--- a/src/tsc/tsc.ts
+++ b/src/tsc/tsc.ts
@@ -19,9 +19,13 @@ namespace ts {
         }
     }
 
+    function defaultIsPretty() {
+        return !!sys.writeOutputIsTTY && sys.writeOutputIsTTY();
+    }
+
     function shouldBePretty(options: CompilerOptions) {
         if (typeof options.pretty === "undefined") {
-            return !!sys.writeOutputIsTTY && sys.writeOutputIsTTY();
+            return defaultIsPretty();
         }
         return options.pretty;
     }
@@ -50,7 +54,7 @@ namespace ts {
 
     export function executeCommandLine(args: string[]): void {
         if (args.length > 0 && ((args[0].toLowerCase() === "--build") || (args[0].toLowerCase() === "-b"))) {
-            const reportDiag = createDiagnosticReporter(sys, /*pretty*/ true);
+            const reportDiag = createDiagnosticReporter(sys, defaultIsPretty());
             const report = (message: DiagnosticMessage, ...args: string[]) => reportDiag(createCompilerDiagnostic(message, ...args));
             const buildHost: BuildHost = {
                 error: report,