Look up executable on PATH when given environment variables.

tests/standalone/io/process_path_environment_test.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.
+//
+// Test that the executable is looked up on the user's PATH when spawning a

[ahe, 2012/10/31 06:46:46]

I don't think this test matches its description. It runs programs that are in
the system's default path, not necessarily the user's.

[Bob Nystrom, 2012/11/01 20:53:03]

My unix knowledge is weak. What's the difference between the system's default
path and the user's?

+// process and environment variables are passed in.
+
+#import('dart:io');
+
+main() {
+  // Pick an app that we expect to be on the PATH that returns 0 when run with
+  // no arguments.
+  var executable = Platform.operatingSystem == 'windows' ? 'cmd.exe' : 'true';
+
+  var options = new ProcessOptions();
+  options.environment = new Map.from(Platform.environment);
+  options.environment['whatever'] = 'something';

[ahe, 2012/10/31 06:46:46]

You're not testing that this environment variable is passed on to the sub
process.

[Bob Nystrom, 2012/11/01 20:53:03]

That's OK, I think. There are other tests that environment variables are
correctly passed. The intent of this test is just to ensure that path lookup
still happens when any environment variables happen to be provided.

+
+  Process.run(executable, [], options).then((result) {
+    Expect.equals(0, result.exitCode);
+  });
+}