- Apply review comments from https://codereview.chromium.org/232223004/

runtime/bin/process_patch.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 patch class _WindowsCodePageDecoder {
   /* patch */ static String _decodeBytes(List<int> bytes)
       native "SystemEncodingToString";
 }
 
 
@@ skipping 163 matching lines @@
       throw new ArgumentError("Arguments is not a List: $arguments");
     }
     int len = arguments.length;
     _arguments = new List<String>(len);
     for (int i = 0; i < len; i++) {
       var arg = arguments[i];
       if (arg is !String) {
         throw new ArgumentError("Non-string argument: $arg");
       }
       _arguments[i] = arguments[i];
-      if (Platform.operatingSystem == 'windows') {
+      if (Platform.isWindows) {
         _arguments[i] = _windowsArgumentEscape(_arguments[i]);
       }
     }
 
     if (_workingDirectory != null && _workingDirectory is !String) {
       throw new ArgumentError(
           "WorkingDirectory is not a String: $_workingDirectory");
     }
 
     _environment = [];
-    var environmentEntryHandler = (key, value) {
+    // Ensure that we have a non-null environment.
+    environment = (environment == null) ? (const {}) : environment;

[Anders Johnsen, 2014/04/10 16:41:20]

if (environment == null) environment = const {};

?

+    if (environment is !Map) {
+      throw new ArgumentError("Environment is not a map: $environment");
+    }
+    environment.forEach((key, value) {
       if (key is !String || value is !String) {
         throw new ArgumentError(
         "Environment key or value is not a string: ($key, $value)");
       }
       _environment.add('$key=$value');
-    };
-    if (environment != null) {
-      if (environment is !Map) {
-        throw new ArgumentError("Environment is not a map: $environment");
-      }
-      environment.forEach(environmentEntryHandler);
-    }
+    });
     if (includeParentEnvironment) {
-      Platform.environment.forEach(environmentEntryHandler);
+      Platform.environment.forEach((key, value) {
+        assert(key is String);
+        assert(value is String);
+        // Do not override keys already set as part of environment.
+        if (!environment.containsKey(key)) {
+          _environment.add('$key=$value');
+        }
+      });
     }
 
     // stdin going to process.
     _stdin = new _StdSink(new _Socket._writePipe());
     // stdout coming from process.
     _stdout = new _StdStream(new _Socket._readPipe());
     // stderr coming from process.
     _stderr = new _StdStream(new _Socket._readPipe());
     _exitHandler = new _Socket._readPipe();
     _ended = false;
     _started = false;
   }
 
   static String _getShellCommand() {
-    if (Platform.operatingSystem == 'windows') {
+    if (Platform.isWindows) {
       return 'cmd.exe';
     }
     return '/bin/sh';
   }
 
   static List<String> _getShellArguments(String executable,
                                          List<String> arguments) {
     List<String> shellArguments = [];
-    if (Platform.operatingSystem == 'windows') {
+    if (Platform.isWindows) {
       shellArguments.add('/c');
       shellArguments.add(executable);
       for (var arg in arguments) {
         shellArguments.add(arg);
       }
     } else {
       var commandLine = new StringBuffer();
       executable = executable.replaceAll("'", "'\"'\"'");
       commandLine.write("'$executable'");
       shellArguments.add("-c");
@@ skipping 69 matching lines @@
       var status = new _ProcessStartStatus();
       bool success = _startNative(_path,
                                   _arguments,
                                   _workingDirectory,
                                   _environment,
                                   _stdin._sink._nativeSocket,
                                   _stdout._stream._nativeSocket,
                                   _stderr._stream._nativeSocket,
                                   _exitHandler._nativeSocket,
                                   status);
-      _environment = null;  // The environment will not be needed going forward.
       if (!success) {
         completer.completeError(
             new ProcessException(_path,
                                  _arguments,
                                  status._errorMessage,
                                  status._errorCode));
         return;
       }
+      // Reset values which are no longer needed.
+      _path = null;
+      _aguments = null;
+      _workingDirectory = null;
+      _environment = null;
+
       _started = true;
 
       // Setup an exit handler to handle internal cleanup and possible
       // callback when a process terminates.
       int exitDataRead = 0;
       final int EXIT_DATA_SIZE = 8;
       List<int> exitDataBuffer = new List<int>(EXIT_DATA_SIZE);
       _exitHandler.listen((data) {
 
         int exitCode(List<int> ints) {
@@ skipping 27 matching lines @@
     var status = new _ProcessStartStatus();
     bool success = _startNative(_path,
                                 _arguments,
                                 _workingDirectory,
                                 _environment,
                                 _stdin._sink._nativeSocket,
                                 _stdout._stream._nativeSocket,
                                 _stderr._stream._nativeSocket,
                                 _exitHandler._nativeSocket,
                                 status);
-    _environment = null;  // The environment will not be needed going forward.
     if (!success) {
       throw new ProcessException(_path,
                                  _arguments,
                                  status._errorMessage,
                                  status._errorCode);
     }
+    // Reset values which are no longer needed.
+    _path = null;
+    _aguments = null;
+    _workingDirectory = null;
+    _environment = null;
 
     var result = _wait(
         _stdin._sink._nativeSocket,
         _stdout._stream._nativeSocket,
         _stderr._stream._nativeSocket,
         _exitHandler._nativeSocket);
 
     getOutput(output, encoding) {
       if (encoding == null) return output;
       return encoding.decode(output);
@@ skipping 139 matching lines @@
   const _ProcessResult(int this.pid,
                        int this.exitCode,
                        this.stdout,
                        this.stderr);
 
   final int pid;
   final int exitCode;
   final stdout;
   final stderr;
 }