Error reporting on File in dart:io

runtime/bin/common.dart

Index: runtime/bin/common.dart
diff --git a/runtime/bin/common.dart b/runtime/bin/common.dart
new file mode 100644
index 0000000000000000000000000000000000000000..fab6033288dc6904ea9c2e2636ea29107dc936f5
--- /dev/null
+++ b/runtime/bin/common.dart
@@ -0,0 +1,49 @@
+// 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.
+
+/**
+  * Class for holding information on an error that was returned from the

[Mads Ager (google), 2012/03/13 10:56:17]

An [OSError] object holds information about an error from the operating system.

?

[Søren Gjesse, 2012/03/13 12:39:49]

Done.

+  * operating system.
+  */
+class OSError {
+  static int noErrorCode = -1;

[Mads Ager (google), 2012/03/13 10:56:17]

This should be final!

[Søren Gjesse, 2012/03/13 12:39:49]

Absolutely, done.

+
+  const OSError([String this.message, int this.errorCode = -1]);

[Mads Ager (google), 2012/03/13 10:56:17]

The -1 here should be noErrorCode?

[Søren Gjesse, 2012/03/13 12:39:49]

Yes, now that noErrorCode is final it can.

+
+  String toString() {
+    StringBuffer sb = new StringBuffer();
+    sb.add("OS Error");
+    if (message != null && message.length > 0) {

[Mads Ager (google), 2012/03/13 10:56:17]

How about making this.message the empty string by default and simplify this
check to !message.isEmpty()

[Søren Gjesse, 2012/03/13 12:39:49]

Done.

+      sb.add(": ");
+      sb.add(message);
+      if (errorCode != noErrorCode) {
+        sb.add(", errno = ");
+        sb.add(errorCode.toString());
+      }
+    } else if (errorCode != noErrorCode) {
+      sb.add(": errno = ");
+      sb.add(errorCode.toString());
+    }
+    return sb.toString();
+  }
+
+  /**
+    * Error message supplied by the operating system. null if no message is
+    * associated with the error.
+    */
+  final String message;
+
+  /**
+    * Error code supplied by the operating system. Will have the value
+    * [noErrorCode] if there is no error code associated with the error.
+    */
+  final int errorCode;
+}
+
+
+// TODO(sgjesse): Remove this once Dart constructors can be invoked

[Mads Ager (google), 2012/03/13 10:56:17]

Please make this an actual doc comment where it says that this should not be
used. It will be removed in an upcoming change. That way it will be clear on
api.dartlang.org if this makes it to there before we can get rid of it.

[Søren Gjesse, 2012/03/13 12:39:49]

Done.

+// through the API.
+class IOUtils {
+  static OSError makeOSError(message, code) => new OSError(message, code);
+}