[python-sybase] Message handling patch

[Ty Sarna]

I've found the handling of messages to be a bit lacking.  Currently some
informational message numbers 5701 and 5703 (database changed, language
changed) are ignored as harmless, but some others are treated as errors
which should not be.  I can't even connect to a Sybase 12.5.2 server
because it returns 5704 (character set changed), and PRINT's and
SHOWPLAN output are also treated as fatal errors. This is especially
annoying in conjunction with the "once you get an error, you're done"
bug (anyone made progress with that?)

The following patch prevents those from raising errors, also adds an
extension to let applications capture these informational messages,
which I also have a use for.

--- Sybase.py.orig	2003-04-27 06:54:35.000000000 -0400
+++ Sybase.py	2004-10-05 15:01:02.000000000 -0400
@@ -129,6 +129,8 @@
 def Binary(str):
     return str
 
+_output_hooks = {}
+
 def _fmt_server(msg):
     parts = []
     for label, name in (('Msg', 'msgnumber'),
@@ -157,8 +159,17 @@
     raise DatabaseError(_fmt_client(msg))
 
 def _servermsg_cb(ctx, conn, msg):
-    if msg.msgnumber not in (5701, 5703):
-        raise DatabaseError(_fmt_server(msg))
+    mn = msg.msgnumber
+    if mn in (0, 5701, 5703, 5704) or ((mn >= 6200) and (mn < 6300)):
+        # Non-errors:
+        #    0      PRINT
+        # 5701      Changed db context
+        # 5703      Changed language
+        # 5704      Changed character set (Sybase)
+        # 6200-6299 SHOWPLAN output (Sybase)
+        _output_hooks.get(conn, lambda c,m: None)(conn, msg)
+    else:
+        raise DatabaseError(_fmt_server(msg.text))
 
 def _row_bind(cmd, count = 1):
     '''Bind buffers for count rows of column data.
@@ -838,6 +849,16 @@
         finally:
             self._unlock()
 
+    def set_output_hook(self, hook):
+        if hook is None:
+            if _output_hooks.has_key(self._conn):
+                del _output_hooks[self._conn]
+        else:
+            _output_hooks[self._conn] = hook
+
+    def get_output_hook(self, hook):
+        return _output_hooks.get(self._conn)
+        
     def __del__(self):
         try:
             self.close()