Rev 5250: join(timeout=0) is useful to check for an exception without stopping the thread. in file:///home/vila/src/bzr/experimental/leaking-tests/

[Vincent Ladeuil]

At file:///home/vila/src/bzr/experimental/leaking-tests/

------------------------------------------------------------
revno: 5250
revision-id: v.ladeuil+lp at free.fr-20100526110529-865s1k26bdj4s9md
parent: v.ladeuil+lp at free.fr-20100526104407-0w315whpmsdeafjk
committer: Vincent Ladeuil <v.ladeuil+lp at free.fr>
branch nick: propagate-exceptions
timestamp: Wed 2010-05-26 13:05:29 +0200
message:
  join(timeout=0) is useful to check for an exception without stopping the thread.
  
  * bzrlib/tests/test_server.py:
  (ThreadWithException.join): Document the timeout=0 idiom.
  
  * bzrlib/tests/test_transport.py:
  (TestThreadWithException.test_exception_is_re_raised): Ensure
  join(timeout=0) can be called while leaving the thread running
-------------- next part --------------
=== modified file 'bzrlib/tests/test_server.py'
--- a/bzrlib/tests/test_server.py	2010-05-26 10:44:07 +0000
+++ b/bzrlib/tests/test_server.py	2010-05-26 11:05:29 +0000
@@ -248,7 +248,12 @@
             self.exception = sys.exc_info()
 
     def join(self, *args, **kwargs):
-        """Overrides Thread.join to raise any exception caught."""
+        """Overrides Thread.join to raise any exception caught.
+
+
+        Calling join(timeout=0) will raise the caught exception or return None
+        is the thread is still alive.
+        """
         # Note that we don't care about the timeout parameter here: either the
         # thread has raised an exception and it should be raised (and join()
         # should succeed whatever the timeout is) or it's still alive which

=== modified file 'bzrlib/tests/test_transport.py'
--- a/bzrlib/tests/test_transport.py	2010-05-26 10:44:07 +0000
+++ b/bzrlib/tests/test_transport.py	2010-05-26 11:05:29 +0000
@@ -1011,3 +1011,21 @@
         tt = test_server.ThreadWithException(target=raise_my_exception)
         tt.start()
         self.assertRaises(MyException, tt.join)
+
+    def test_join_when_no_exception(self):
+        resume = threading.Event()
+        class MyException(Exception):
+            pass
+
+        def raise_my_exception():
+            # Wait for the test to tell us to resume
+            resume.wait()
+            # Now we can raise
+            raise MyException()
+
+        tt = test_server.ThreadWithException(target=raise_my_exception)
+        tt.start()
+        tt.join(timeout=0)
+        self.assertIs(None, tt.exception)
+        resume.set()
+        self.assertRaises(MyException, tt.join)