From 02ebfa5d115104653eeff83a1f58ab14ed1c9420 Mon Sep 17 00:00:00 2001
From: Ron Buckton <rbuckton@microsoft.com>
Date: Mon, 21 Mar 2016 11:54:10 -0700
Subject: [PATCH] Added environment variable to force experimental
 transformations.

---
 Jakefile.js             | 11 +++--------
 src/compiler/program.ts |  5 +++++
 src/compiler/sys.ts     | 12 ++++++++++--
 src/compiler/tsc.ts     |  2 +-
 4 files changed, 19 insertions(+), 11 deletions(-)

diff --git a/Jakefile.js b/Jakefile.js
index fdde2ea9dbd..e9e5fc31912 100644
--- a/Jakefile.js
+++ b/Jakefile.js
@@ -241,7 +241,6 @@ function concatenateFiles(destinationFile, sourceFiles) {
 }
 
 var useDebugMode = true;
-var useTransforms = process.env.USE_TRANSFORMS || false;
 var host = (process.env.host || process.env.TYPESCRIPT_HOST || "node");
 var compilerFilename = "tsc.js";
 var LKGCompiler = path.join(LKGDirectory, compilerFilename);
@@ -309,8 +308,8 @@ function compileFile(outFile, sources, prereqs, prefixes, useBuiltCompiler, opts
             options += " --stripInternal"
         }
 
-        if (useBuiltCompiler && useTransforms) {
-            options += " --experimentalTransforms"
+        if (useBuiltCompiler && Boolean(process.env.USE_TRANSFORMS)) {
+            console.warn("\u001b[93mwarning: Found 'USE_TRANSFORMS' environment variable. Experimental transforms will be enabled by default.\u001b[0m");
         }
 
         var cmd = host + " " + compilerPath + " " + options + " ";
@@ -430,10 +429,6 @@ task("setDebugMode", function() {
     useDebugMode = true;
 });
 
-task("setTransforms", function() {
-    useTransforms = true;
-});
-
 task("configure-nightly", [configureNightlyJs], function() {
     var cmd = host + " " + configureNightlyJs + " " + packageJson + " " + programTs;
     console.log(cmd);
@@ -519,7 +514,7 @@ compileFile(servicesFileInBrowserTest, servicesSources,[builtLocalDirectory, cop
                 var i = content.lastIndexOf("\n");
                 fs.writeFileSync(servicesFileInBrowserTest, content.substring(0, i) + "\r\n//# sourceURL=../built/local/typeScriptServices.js" + content.substring(i));
             });
-    
+
 
 var serverFile = path.join(builtLocalDirectory, "tsserver.js");
 compileFile(serverFile, serverSources,[builtLocalDirectory, copyright].concat(serverSources), /*prefixes*/ [copyright], /*useBuiltCompiler*/ true);
diff --git a/src/compiler/program.ts b/src/compiler/program.ts
index 7ec3c7a0f47..29e44ca11f5 100644
--- a/src/compiler/program.ts
+++ b/src/compiler/program.ts
@@ -994,6 +994,11 @@ namespace ts {
 
             const start = new Date().getTime();
 
+            // TODO(rbuckton): remove USE_TRANSFORMS condition when we switch to transforms permenantly.
+            if (Boolean(sys.getEnvironmentVariable("USE_TRANSFORMS"))) {
+                options.experimentalTransforms = true;
+            }
+
             const fileEmitter = options.experimentalTransforms ? printFiles : emitFiles;
             const emitResult = fileEmitter(
                 emitResolver,
diff --git a/src/compiler/sys.ts b/src/compiler/sys.ts
index c1920884b22..fce9408caf0 100644
--- a/src/compiler/sys.ts
+++ b/src/compiler/sys.ts
@@ -8,7 +8,6 @@ namespace ts {
         args: string[];
         newLine: string;
         useCaseSensitiveFileNames: boolean;
-        /*@internal*/ developmentMode?: boolean;
         write(s: string): void;
         readFile(path: string, encoding?: string): string;
         writeFile(path: string, data: string, writeByteOrderMark?: boolean): void;
@@ -23,6 +22,7 @@ namespace ts {
         readDirectory(path: string, extension?: string, exclude?: string[]): string[];
         getMemoryUsage?(): number;
         exit(exitCode?: number): void;
+        /*@internal*/ getEnvironmentVariable(name: string): string;
         /*@internal*/ tryEnableSourceMapsForHost?(): void;
     }
 
@@ -213,6 +213,9 @@ namespace ts {
                 getCurrentDirectory() {
                     return new ActiveXObject("WScript.Shell").CurrentDirectory;
                 },
+                getEnvironmentVariable(name: string) {
+                    return new ActiveXObject("WScript.Shell").ExpandEnvironmentStrings(`%${name}%`);
+                },
                 readDirectory,
                 exit(exitCode?: number): void {
                     try {
@@ -523,7 +526,6 @@ namespace ts {
                 args: process.argv.slice(2),
                 newLine: _os.EOL,
                 useCaseSensitiveFileNames: useCaseSensitiveFileNames,
-                developmentMode: /^development$/i.test(String(process.env.NODE_ENV)),
                 write(s: string): void {
                     process.stdout.write(s);
                 },
@@ -581,6 +583,9 @@ namespace ts {
                 getCurrentDirectory() {
                     return process.cwd();
                 },
+                getEnvironmentVariable(name: string) {
+                    return process.env[name] || "";
+                },
                 readDirectory,
                 getMemoryUsage() {
                     if (global.gc) {
@@ -627,6 +632,9 @@ namespace ts {
                 createDirectory: ChakraHost.createDirectory,
                 getExecutingFilePath: () => ChakraHost.executingFile,
                 getCurrentDirectory: () => ChakraHost.currentDirectory,
+                getEnvironmentVariable(name: string) {
+                    return "";
+                },
                 readDirectory: ChakraHost.readDirectory,
                 exit: ChakraHost.quit,
             };
diff --git a/src/compiler/tsc.ts b/src/compiler/tsc.ts
index bf16b274d9b..789db5a1faf 100644
--- a/src/compiler/tsc.ts
+++ b/src/compiler/tsc.ts
@@ -781,7 +781,7 @@ namespace ts {
     }
 }
 
-if (ts.sys.developmentMode && ts.sys.tryEnableSourceMapsForHost) {
+if (ts.sys.tryEnableSourceMapsForHost && /^development$/i.test(ts.sys.getEnvironmentVariable("NODE_ENV"))) {
     ts.sys.tryEnableSourceMapsForHost();
 }