Stop hiding errors that occur inside __del__ methods

If an exception occurs inside the __del__ method, it should be reported
to the developer. Not doing so could hide bugs.

Python automatically handles exceptions inside __del__ methods, for
example:

    class A:
        def __del__(self):
            1 / 0

    A()
    print("after del")

Results in the output:

    $ python3 ~/blah.py
    Exception ignored in: <function A.__del__ at 0x7fbbf2bbfc20>
    Traceback (most recent call last):
      File "/home/jon/test.py", line 3, in __del__
        1 / 0
    ZeroDivisionError: division by zero
    after del

From this example, we can see the bug was not hidden and the code after
__del__ still executed.

fixes #1281

3 files changed, 16 insertions, 24 deletions

diff --git a/CHANGES b/CHANGES
index 7fac16f..94c8ccb 100644
--- a/CHANGES
+++ b/CHANGES
@@ -1,3 +1,10 @@
+* (in development)
+    * Removed exception trapping from __del__ methods. redis-py objects that
+      hold various resources implement __del__ cleanup methods to release
+      those resources when the object goes out of scope. This provides a
+      fallback for when these objects aren't explicitly closed by user code.
+      Prior to this change any errors encountered in closing these resources
+      would be hidden from the user. Thanks @jdufresne. #1281
 * 3.4.1
     * Move the username argument in the Redis and Connection classes to the
       end of the argument list. This helps those poor souls that specify all
@@ -14,7 +21,7 @@
       in 3.4.0. This ended up being a bad idea as two separate connection
       pools be considered equal yet manage a completely separate set of
       connections.
-    * HSET command now can accept multiple pairs. HMSET has been marked as 
+    * HSET command now can accept multiple pairs. HMSET has been marked as
       deprecated now. Thanks to @laixintao #1271
 * 3.4.0
     * Allow empty pipelines to be executed if there are WATCHed keys.
diff --git a/redis/client.py b/redis/client.py
index fe697f6..9cb60f5 100755
--- a/redis/client.py
+++ b/redis/client.py
@@ -3375,13 +3375,10 @@ class PubSub(object):
         self.reset()
 
     def __del__(self):
-        try:
-            # if this object went out of scope prior to shutting down
-            # subscriptions, close the connection manually before
-            # returning it to the connection pool
-            self.reset()
-        except Exception:
-            pass
+        # if this object went out of scope prior to shutting down
+        # subscriptions, close the connection manually before
+        # returning it to the connection pool
+        self.reset()
 
     def reset(self):
         if self.connection:
@@ -3730,10 +3727,7 @@ class Pipeline(Redis):
         self.reset()
 
     def __del__(self):
-        try:
-            self.reset()
-        except Exception:
-            pass
+        self.reset()
 
     def __len__(self):
         return len(self.command_stack)
diff --git a/redis/connection.py b/redis/connection.py
index b5e3fb1..dbcf332 100755
--- a/redis/connection.py
+++ b/redis/connection.py
@@ -288,10 +288,7 @@ class PythonParser(BaseParser):
         self._buffer = None
 
     def __del__(self):
-        try:
-            self.on_disconnect()
-        except Exception:
-            pass
+        self.on_disconnect()
 
     def on_connect(self, connection):
         "Called when the socket connects"
@@ -370,10 +367,7 @@ class HiredisParser(BaseParser):
             self._buffer = bytearray(socket_read_size)
 
     def __del__(self):
-        try:
-            self.on_disconnect()
-        except Exception:
-            pass
+        self.on_disconnect()
 
     def on_connect(self, connection):
         self._sock = connection._sock
@@ -533,10 +527,7 @@ class Connection(object):
         return pieces
 
     def __del__(self):
-        try:
-            self.disconnect()
-        except Exception:
-            pass
+        self.disconnect()
 
     def register_connect_callback(self, callback):
         self._connect_callbacks.append(callback)