Use random debug port in basic_debugger_test.

tests/standalone/debugger/basic_debugger_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.
 
 // This test forks a second vm process that runs this dart script as
 // a debug target.
 // Run this test with option --wire to see the json messages sent
 // between the processes.
 // Run this test with option --verbose to see the stdout and stderr output
 // of the debug target process.
 
 import "debug_lib.dart";
+import "dart:io";
+import "dart:math";
+
+var debugPort;
+var retries = 0;
+var random = new Random();

[hausner, 2013/03/28 00:31:21]

Does this generate a different random number each time you run the test? Or is
it a pseudo random number generator? If it's the latter, you need to seed or
randomize it, e.g. with a time value.

This does not need to be a global variable, right?

[Tom Ball, 2013/03/28 18:19:43]

Updated to use current time in milliseconds as seed (too bad there's no way to
get a process id), and moved to a stack variable.

 
 bar(x) {
   print(x);
 }
 
 foo(i) {
   bar("baz");
   print(i);
 }
 
-main() {
-  if (RunScript(testScript)) return;
+void runTest() {
+  if (RunScript(testScript, debugPort)) return;
   print("Hello from debuggee");
   foo(42);
   print("Hello again");
 }
 
+void main() {

[hausner, 2013/03/28 00:31:21]

It might be more convenient to put this functionality into debug_lib.dart, so
that not every test has to implement it.

[Tom Ball, 2013/03/28 18:19:43]

Done -- this reverted all changes to this specific test.

+  var options = new Options();
+  if (options.arguments.contains("--debuggee")) {
+    runTest();
+  } else {
+    // Pick a port in the upper half of the port number range.
+    debugPort = random.nextInt(32000) + 32000;
+    print('using debug port $debugPort ...');
+    ServerSocket.bind('127.0.0.1', debugPort).then((ServerSocket s) {
+        s.close();
+        runTest();
+      },
+      onError: (e) {
+        if (++retries >= 3) { 
+          print('unable to find unused port: $e');
+          return -1; 
+        } else {
+          // Retry with another random port.
+          main();
+        }
+      });
+  }
+}
 
 // Expected debugger events and commands.
 var testScript = [
   Breakpoint(),  // Expect a breakpoint event.
   MatchFrame(0, "main"),  // Top frame in trace is function "main".
   Step(),
   Breakpoint(function: "main"),
-  SetBreakpoint(15),  // Set breakpoint a line 15, in function bar.
+  SetBreakpoint(21),  // Set breakpoint a line 21, in function bar.
   Resume(),
   Breakpoint(function: "bar"),
-  MatchFrames(["bar", "foo", "main"]),
+  MatchFrames(["bar", "foo", "runTest", "main"]),
   MatchFrame(1, "foo"),
   Resume(),
 ];