Ignore all environment variables with name starting with '='

sdk/lib/io/platform_impl.dart

 // Copyright (c) 2012, 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.
 
 part of dart.io;
 
 class _Platform {
   external static int _numberOfProcessors();
   external static String _pathSeparator();
   external static String _operatingSystem();
@@ skipping 40 matching lines @@
 
   static List<String> get executableArguments => _executableArguments();
 
   static Map<String, String> get environment {
     if (_environmentCache == null) {
       var env = _environment();
       if (env is !OSError) {
         var isWindows = operatingSystem == 'windows';
         var result = isWindows ? new _CaseInsensitiveStringMap() : new Map();
         for (var str in env) {
-          // When running on Windows through cmd.exe there are strange
-          // environment variables that are used to record the current
-          // working directory for each drive and the exit code for the
-          // last command. As an example: '=A:=A:\subdir' records the
-          // current working directory on the 'A' drive.  In order to
-          // handle these correctly we search for a second occurrence of
-          // of '=' in the string if the first occurrence is at index 0.
+          // When running on Windows through cmd.exe there are
+          // entries which starts with '='. In CMD scripting,
+          // variables are "dynamic" environment variables which change
+          // automatically. The values of the ones starting with "=" are
+          // reified in the environment string of a new program (but, e.g.,
+          // __CD__ isn't).
+          //
+          // One example are the use of the environment to communicate the
+          // current working directory for each drive and the exit code for the
+          // last command. E.g. the entry '=A:=A:\subdir' records the current
+          // working directory on the 'A' drive.
+          //
+          // On Mac OS an entry of just '=' has been seen.
+          //
+          // Entries starting with '=' are ignored.
+          //
+          // Entries with no '=' should not happen. If it should happen,
+          // the entry is ignored.
           var equalsIndex = str.indexOf('=');
-          if (equalsIndex == 0) {
-            equalsIndex = str.indexOf('=', 1);
+          if (equalsIndex > 0) {
+            result[str.substring(0, equalsIndex)] =
+                str.substring(equalsIndex + 1);
           }
-          assert(equalsIndex != -1);
-          result[str.substring(0, equalsIndex)] =
-              str.substring(equalsIndex + 1);
         }
         _environmentCache = new UnmodifiableMapView<String, String>(result);
       } else {
         _environmentCache = env;
       }
     }
 
     if (_environmentCache is OSError) {
       throw _environmentCache;
     } else {
@@ skipping 24 matching lines @@
   V remove(String key) => _map.remove(key.toUpperCase());
   void clear() => _map.clear();
   void forEach(void f(String key, V value)) => _map.forEach(f);
   Iterable<String> get keys => _map.keys;
   Iterable<V> get values => _map.values;
   int get length => _map.length;
   bool get isEmpty => _map.isEmpty;
   bool get isNotEmpty => _map.isNotEmpty;
   String toString() => _map.toString();
 }