Warning propagation improvements

MySQLdb/cursors.py

@@ -73,8 +73,7 @@ class BaseCursor(object):
         self.messages = []
         self.errorhandler = connection.errorhandler
         self._result = None
-        self._warnings = 0
-        self._info = None
+        self._warnings = None
         self.rownumber = None
 
     def close(self):
@@ -128,29 +127,37 @@ class BaseCursor(object):
 
     def _warning_check(self):
         from warnings import warn
+        db = self._get_db()
+
+        # None => warnings not interrogated for current query yet
+        # 0 => no warnings exists or have been handled already for this query
+        if self._warnings is None:
+            self._warnings = db.warning_count()
         if self._warnings:
+            # Only propagate warnings for current query once
+            warning_count = self._warnings
+            self._warnings = 0
             # When there is next result, fetching warnings cause "command
             # out of sync" error.
             if self._result and self._result.has_next:
-                msg = "There are %d MySQL warnings." % (self._warnings,)
+                msg = "There are %d MySQL warnings." % (warning_count,)
                 self.messages.append(msg)
-                warn(msg, self.Warning, 3)
+                warn(self.Warning(0, msg), stacklevel=3)
                 return
 
-            warnings = self._get_db().show_warnings()
+            warnings = db.show_warnings()
             if warnings:
                 # This is done in two loops in case
                 # Warnings are set to raise exceptions.
                 for w in warnings:
                     self.messages.append((self.Warning, w))
                 for w in warnings:
-                    msg = w[-1]
-                    if not PY2 and isinstance(msg, bytes):
-                        msg = msg.decode()
-                    warn(msg, self.Warning, 3)
-            elif self._info:
-                self.messages.append((self.Warning, self._info))
-                warn(self._info, self.Warning, 3)
+                    warn(self.Warning(*w[1:3]), stacklevel=3)
+            else:
+                info = db.info()
+                if info:
+                    self.messages.append((self.Warning, info))
+                    warn(self.Warning(0, info), stacklevel=3)
 
     def nextset(self):
         """Advance to the next result set.
@@ -180,8 +187,7 @@ class BaseCursor(object):
         self.description = self._result and self._result.describe() or None
         self.description_flags = self._result and self._result.field_flags() or None
         self.lastrowid = db.insert_id()
-        self._warnings = db.warning_count()
-        self._info = db.info()
+        self._warnings = None
 
     def setinputsizes(self, *args):
         """Does nothing, required by DB API."""

tests/test_MySQLdb_capabilities.py

@@ -3,6 +3,8 @@ import capabilities
 from datetime import timedelta
 import unittest
 import MySQLdb
+from MySQLdb.compat import unicode
+from MySQLdb import cursors
 import warnings
 
 
@@ -155,6 +157,28 @@ class test_MySQLdb(capabilities.DatabaseTest):
             return
         self.fail("Should raise ProgrammingError")
 
+    def test_warning_propagation(self):
+        with warnings.catch_warnings():
+            # Ignore all warnings other than MySQLdb generated ones
+            warnings.simplefilter("ignore")
+            warnings.simplefilter("error", category=MySQLdb.Warning)
+
+            # verify for both buffered and unbuffered cursor types
+            for cursor_class in (cursors.Cursor, cursors.SSCursor):
+                c = self.connection.cursor(cursor_class)
+                try:
+                    c.execute("SELECT CAST('124b' AS SIGNED)")
+                    c.fetchall()
+                except MySQLdb.Warning as e:
+                    # Warnings should have errorcode and string message, just like exceptions
+                    self.assertEqual(len(e.args), 2)
+                    self.assertEqual(e.args[0], 1292)
+                    self.assertTrue(isinstance(e.args[1], unicode))
+                else:
+                    self.fail("Should raise Warning")
+                finally:
+                    c.close()
+
 
 if __name__ == '__main__':
     if test_MySQLdb.leak_test: