pkg/test: handle symlinked dart executable

lib/src/util/io.dart

Index: lib/src/util/io.dart
diff --git a/lib/src/util/io.dart b/lib/src/util/io.dart
index dbe34f4e01ff7965590232a7a83c39c58b672b53..fa52b370e94513a4eb07eed1e4cba66f7af826d9 100644
--- a/lib/src/util/io.dart
+++ b/lib/src/util/io.dart
@@ -20,9 +20,18 @@ const _newline = 0xA;
 /// The ASCII code for a carriage return character.
 const _carriageReturn = 0xD;
 
+String _sdkDir;

[nweiz, 2015/05/15 20:04:50]

For lazy top-level variables, I like to take advantage of Dart's built-in lazy
initialization and write something like:

final String sdkDir = (() {
  // ...
})();

[kevmoo, 2015/05/21 17:46:22]

Done.

+
 /// The root directory of the Dart SDK.
-final String sdkDir =
-    p.dirname(p.dirname(Platform.executable));
+String get sdkDir {

[nweiz, 2015/05/15 20:04:50]

Add a TODO to get rid of this variable when Platform.sdkPath exists.

[kevmoo, 2015/05/21 17:46:22]

Not sure if that's going to happen, given the current discussion.

[nweiz, 2015/05/21 19:06:01]

A TODO to simplify it when Platform.executable is reliable would be fine, too.
Just make sure to link it to the appropriate issue.

+  if (_sdkDir == null) {
+    // This may fail on Mac if `dart` is run directly from the PATH environment

[nweiz, 2015/05/15 20:04:50]

What does "run directly from the PATH environment" mean? Also, it seems like a
problem if this can still fail.

[kevmoo, 2015/05/21 17:46:22]

Acknowledged.

+    // See https://code.google.com/p/dart/issues/detail?id=21791

[nweiz, 2015/05/15 20:04:50]

What does this issue have to do with it?

[kevmoo, 2015/05/21 17:46:22]

Acknowledged.

+    var path = new File(Platform.executable).resolveSymbolicLinksSync();

[nweiz, 2015/05/15 20:04:50]

What if the bin directory is symlinked rather than the executable?

[kevmoo, 2015/05/21 17:46:22]

This still works. resolveSymbolicLinks does the work to walk out of directories
that have been symlinked, too

+    _sdkDir = p.dirname(p.dirname(path));
+  }
+  return _sdkDir;
+}
 
 /// The version of the Dart SDK currently in use.
 final Version _sdkVersion = new Version.parse(