BUG#21463298: Fix weakly-referenced object no longer exists exception

nmariz · nmariz · commit 70d5bafcd52c · 2022-07-29T16:52:07.000+01:00
Connector/Python cursors contain a weak reference to the connection,
and a weak reference to an object is not enough to keep the object
alive. So when the connection object is destroyed and the cursor is
used, a ReferenceError exception is raised saying that the
weakly-referenced object no longer exists.

With this patch a ProgrammingError exception is raised instead saying
the cursor is not connected.

Change-Id: I843a9e84185f8b8710383dd18d9df54910bc5840
diff --git a/CHANGES.txt b/CHANGES.txt
@@ -17,6 +17,7 @@ v8.0.31
 - BUG#28491115: Connector/Python crashes on 0 time value
 - BUG#28295478: Align exception types raised by pure Python and c-ext
 - BUG#27634910: Add warning count method to cursors
+- BUG#21463298: Fix weakly-referenced object no longer exists exception
 
 v8.0.30
 =======
diff --git a/lib/mysql/connector/cursor.py b/lib/mysql/connector/cursor.py
@@ -520,8 +520,11 @@ def execute(self, operation, params=None, multi=False):
         if not operation:
             return None
 
-        if not self._connection:
-            raise ProgrammingError("Cursor is not connected")
+        try:
+            if not self._connection:
+                raise ProgrammingError
+        except (ProgrammingError, ReferenceError) as err:
+            raise ProgrammingError("Cursor is not connected") from err
 
         self._connection.handle_unread_result()
 
diff --git a/lib/mysql/connector/cursor_cext.py b/lib/mysql/connector/cursor_cext.py
@@ -244,8 +244,11 @@ def execute(self, operation, params=(), multi=False):
         if not operation:
             return None
 
-        if not self._cnx or self._cnx.is_closed():
-            raise ProgrammingError("Cursor is not connected", 2055)
+        try:
+            if not self._cnx or self._cnx.is_closed():
+                raise ProgrammingError
+        except (ProgrammingError, ReferenceError) as err:
+            raise ProgrammingError("Cursor is not connected", 2055) from err
         self._cnx.handle_unread_result()
 
         stmt = ""
@@ -352,8 +355,11 @@ def executemany(self, operation, seq_params):
         if not operation or not seq_params:
             return None
 
-        if not self._cnx:
-            raise ProgrammingError("Cursor is not connected")
+        try:
+            if not self._cnx:
+                raise ProgrammingError
+        except (ProgrammingError, ReferenceError) as err:
+            raise ProgrammingError("Cursor is not connected") from err
         self._cnx.handle_unread_result()
 
         if not isinstance(seq_params, (list, tuple)):
@@ -1008,8 +1014,11 @@ def execute(self, operation, params=None, multi=False):  # multi is unused
         if not operation:
             return
 
-        if not self._cnx or self._cnx.is_closed():
-            raise ProgrammingError("Cursor is not connected", 2055)
+        try:
+            if not self._cnx or self._cnx.is_closed():
+                raise ProgrammingError
+        except (ProgrammingError, ReferenceError) as err:
+            raise ProgrammingError("Cursor is not connected", 2055) from err
 
         self._cnx.handle_unread_result(prepared=True)
 
diff --git a/tests/test_bugs.py b/tests/test_bugs.py
@@ -7020,3 +7020,28 @@ def test_binary_data_started_with_0x00(self):
             res = cur.fetchall()
             self.assertEqual(exp, res)
             cur.execute(f"DROP TABLE IF EXISTS {table_name}")
+
+
+class BugOra21463298(tests.MySQLConnectorTests):
+    """BUG#21463298: Fix weakly-referenced object no longer exists exception.
+
+    Connector/Python cursors contain a weak reference to the connection,
+    and a weak reference to an object is not enough to keep the object
+    alive. So when the connection object is destroyed and the cursor is
+    used, a ReferenceError exception is raised saying that the
+    weakly-referenced object no longer exists.
+
+    With this patch a ProgrammingError exception is raised instead saying
+    the cursor is not connected.
+    """
+
+    @foreach_cnx()
+    def test_weakly_referenced_error(self):
+        config = tests.get_mysql_config()
+
+        def get_cursor():
+            return self.cnx.__class__(**config).cursor()
+
+        with self.assertRaises(errors.ProgrammingError) as context:
+            get_cursor().execute("SELECT SLEEP(1)")
+        self.assertEqual(context.exception.msg, "Cursor is not connected")
