Imaplib2: use proper tracebacks for exceptions

Get real tracebacks (at the point that calls Request.abort()
and not from the point that handles collected abort requests)
and pass them to our calling functions to ease debugging
of user problems.

Signed-off-by: Eygene Ryabinkin <rea@codelabs.ru>

offlineimap/imaplib2.py

@@ -48,7 +48,7 @@ __author__ = "Piers Lauder <piers@janeelix.com>"
 __URL__ = "http://imaplib2.sourceforge.net"
 __license__ = "Python License"
 
-import binascii, errno, os, Queue, random, re, select, socket, sys, time, threading, zlib
+import binascii, errno, os, Queue, random, re, select, socket, sys, time, threading, traceback, zlib
 
 select_module = select
 
@@ -160,21 +160,25 @@ class Request(object):
         self.data = None
 
 
-    def abort(self, typ, val):
-        self.aborted = (typ, val)
+    def abort_tb(self, typ, val, tb):
+        self.aborted = (typ, val, tb)
         self.deliver(None)
 
 
+    def abort(self, typ, val):
+        self.abort_tb(typ, val, traceback.extract_stack())
+
+
     def get_response(self, exc_fmt=None):
         self.callback = None
         if __debug__: self.parent._log(3, '%s:%s.ready.wait' % (self.name, self.tag))
         self.ready.wait()
 
         if self.aborted is not None:
-            typ, val = self.aborted
+            typ, val, tb = self.aborted
             if exc_fmt is None:
                 exc_fmt = '%s - %%s' % typ
-            raise typ(exc_fmt % str(val))
+            raise typ, typ(exc_fmt % str(val)), tb
 
         return self.response
 
@@ -1661,7 +1665,7 @@ class IMAP4(object):
 
         if __debug__: self._log(1, 'starting')
 
-        typ, val = self.abort, 'connection terminated'
+        typ, val, tb = self.abort, 'connection terminated', None
 
         while not self.Terminate:
 
@@ -1684,6 +1688,7 @@ class IMAP4(object):
                     if resp_timeout is not None and self.tagged_commands:
                         if __debug__: self._log(1, 'response timeout')
                         typ, val = self.abort, 'no response after %s secs' % resp_timeout
+                        tb = traceback.extract_stack()
                         break
                     continue
                 if self.idle_timeout > time.time():
@@ -1695,23 +1700,33 @@ class IMAP4(object):
                 if __debug__: self._log(1, 'inq None - terminating')
                 break
 
+            # self.inq can contain tuple, it means we got an exception.
+            # For example of code that produces tuple see IMAP4._reader()
+            # and IMAP4._writer().
+            #
+            # XXX: may be it will be more explicit to create own exception
+            # XXX: class and pass it instead of tuple.
             if not isinstance(line, basestring):
-                typ, val = line
+                typ, val, tb = line
                 break
 
             try:
                 self._put_response(line)
             except:
                 typ, val = self.error, 'program error: %s - %s' % sys.exc_info()[:2]
+                tb = sys.exc_info()[2]
                 break
 
         self.Terminate = True
 
+        if not tb:
+            tb = traceback.extract_stack()
+
         if __debug__: self._log(1, 'terminating: %s' % repr(val))
 
         while not self.ouq.empty():
             try:
-                self.ouq.get_nowait().abort(typ, val)
+                self.ouq.get_nowait().abort_tb(typ, val, tb)
             except Queue.Empty:
                 break
         self.ouq.put(None)
@@ -1719,7 +1734,7 @@ class IMAP4(object):
         self.commands_lock.acquire()
         for name in self.tagged_commands.keys():
             rqb = self.tagged_commands.pop(name)
-            rqb.abort(typ, val)
+            rqb.abort_tb(typ, val, tb)
         self.state_change_free.set()
         self.commands_lock.release()
         if __debug__: self._log(3, 'state_change_free.set')
@@ -1801,7 +1816,7 @@ class IMAP4(object):
                         self._print_log()
                         if self.debug: self.debug += 4          # Output all
                         self._log(1, reason)
-                self.inq.put((self.abort, reason))
+                self.inq.put((self.abort, reason, sys.exc_info()[2]))
                 break
 
         poll.unregister(self.read_fd)
@@ -1865,7 +1880,7 @@ class IMAP4(object):
                         self._print_log()
                         if self.debug: self.debug += 4          # Output all
                         self._log(1, reason)
-                self.inq.put((self.abort, reason))
+                self.inq.put((self.abort, reason, sys.exc_info()[2]))
                 break
 
         if __debug__: self._log(1, 'finished')
@@ -1878,6 +1893,7 @@ class IMAP4(object):
         if __debug__: self._log(1, 'starting')
 
         reason = 'Terminated'
+        tb = None
 
         while not self.Terminate:
             rqb = self.ouq.get()
@@ -1889,15 +1905,19 @@ class IMAP4(object):
                 if __debug__: self._log(4, '> %s' % rqb.data)
             except:
                 reason = 'socket error: %s - %s' % sys.exc_info()[:2]
+                tb = sys.exc_info()[2]
                 if __debug__:
                     if not self.Terminate:
                         self._print_log()
                         if self.debug: self.debug += 4          # Output all
                         self._log(1, reason)
-                rqb.abort(self.abort, reason)
+                rqb.abort_tb(self.abort, reason, tb)
                 break
 
-        self.inq.put((self.abort, reason))
+        if not tb:
+            tb = traceback.extract_stack()
+
+        self.inq.put((self.abort, reason, tb))
 
         if __debug__: self._log(1, 'finished')