Refactored database exceptions wrapping.

Squashed commit of the following:

commit 2181d833ed1a2e422494738dcef311164c4e097e
Author: Aymeric Augustin <aymeric.augustin@m4x.org>
Date:   Wed Feb 27 14:28:39 2013 +0100

    Fixed #15901 -- Wrapped all PEP-249 exceptions.

commit 5476a5d93c19aa2f928c497d39ce6e33f52694e2
Author: Aymeric Augustin <aymeric.augustin@m4x.org>
Date:   Tue Feb 26 17:26:52 2013 +0100

    Added PEP 3134 exception chaining.

    Thanks Jacob Kaplan-Moss for the suggestion.

commit 9365fad0a650328002fb424457d675a273c95802
Author: Aymeric Augustin <aymeric.augustin@m4x.org>
Date:   Tue Feb 26 17:13:49 2013 +0100

    Improved API for wrapping database errors.

    Thanks Alex Gaynor for the proposal.

commit 1b463b765f2826f73a8d9266795cd5da4f8d5e9e
Author: Aymeric Augustin <aymeric.augustin@m4x.org>
Date:   Tue Feb 26 15:00:39 2013 +0100

    Removed redundant exception wrapping.

    This is now taken care of by the cursor wrapper.

commit 524bc7345a724bf526bdd2dd1bcf5ede67d6bb5c
Author: Aymeric Augustin <aymeric.augustin@m4x.org>
Date:   Tue Feb 26 14:55:10 2013 +0100

    Wrapped database exceptions in the base backend.

    This covers the most common PEP-249 APIs:
    - Connection APIs: close(), commit(), rollback(), cursor()
    - Cursor APIs: callproc(), close(), execute(), executemany(),
      fetchone(), fetchmany(), fetchall(), nextset().

    Fixed #19920.

commit a66746bb5f0839f35543222787fce3b6a0d0a3ea
Author: Aymeric Augustin <aymeric.augustin@m4x.org>
Date:   Tue Feb 26 14:53:34 2013 +0100

    Added a wrap_database_exception context manager and decorator.

    It re-throws backend-specific exceptions using Django's common wrappers.

10 files changed, 147 insertions, 100 deletions

diff --git a/django/db/__init__.py b/django/db/__init__.py
index 32e42bbfe9..e76c6c3268 100644
--- a/django/db/__init__.py
+++ b/django/db/__init__.py
@@ -1,8 +1,11 @@
 from django.conf import settings
 from django.core import signals
 from django.core.exceptions import ImproperlyConfigured
-from django.db.utils import (ConnectionHandler, ConnectionRouter,
-    load_backend, DEFAULT_DB_ALIAS, DatabaseError, IntegrityError)
+from django.db.utils import (DEFAULT_DB_ALIAS,
+    DataError, OperationalError, IntegrityError, InternalError,
+    ProgrammingError, NotSupportedError, DatabaseError,
+    InterfaceError, Error,
+    load_backend, ConnectionHandler, ConnectionRouter)
 
 __all__ = ('backend', 'connection', 'connections', 'router', 'DatabaseError',
     'IntegrityError', 'DEFAULT_DB_ALIAS')
diff --git a/django/db/backends/__init__.py b/django/db/backends/__init__.py
index 46db1910f9..49e07cfa9e 100644
--- a/django/db/backends/__init__.py
+++ b/django/db/backends/__init__.py
@@ -14,6 +14,7 @@ from django.db import DEFAULT_DB_ALIAS
 from django.db.backends.signals import connection_created
 from django.db.backends import util
 from django.db.transaction import TransactionManagementError
+from django.db.utils import DatabaseErrorWrapper
 from django.utils.functional import cached_property
 from django.utils.importlib import import_module
 from django.utils import six
@@ -57,6 +58,9 @@ class BaseDatabaseWrapper(object):
     def __hash__(self):
         return hash(self.alias)
 
+    def wrap_database_errors(self):
+        return DatabaseErrorWrapper(self.Database)
+
     def get_connection_params(self):
         raise NotImplementedError
 
@@ -70,20 +74,28 @@ class BaseDatabaseWrapper(object):
         raise NotImplementedError
 
     def _cursor(self):
-        if self.connection is None:
-            conn_params = self.get_connection_params()
-            self.connection = self.get_new_connection(conn_params)
-            self.init_connection_state()
-            connection_created.send(sender=self.__class__, connection=self)
-        return self.create_cursor()
+        with self.wrap_database_errors():
+            if self.connection is None:
+                conn_params = self.get_connection_params()
+                self.connection = self.get_new_connection(conn_params)
+                self.init_connection_state()
+                connection_created.send(sender=self.__class__, connection=self)
+            return self.create_cursor()
 
     def _commit(self):
         if self.connection is not None:
-            return self.connection.commit()
+            with self.wrap_database_errors():
+                return self.connection.commit()
 
     def _rollback(self):
         if self.connection is not None:
-            return self.connection.rollback()
+            with self.wrap_database_errors():
+                return self.connection.rollback()
+
+    def _close(self):
+        if self.connection is not None:
+            with self.wrap_database_errors():
+                return self.connection.close()
 
     def _enter_transaction_management(self, managed):
         """
@@ -333,8 +345,9 @@ class BaseDatabaseWrapper(object):
 
     def close(self):
         self.validate_thread_sharing()
-        if self.connection is not None:
-            self.connection.close()
+        try:
+            self._close()
+        finally:
             self.connection = None
         self.set_clean()
 
diff --git a/django/db/backends/mysql/base.py b/django/db/backends/mysql/base.py
index fc2ff31581..4bfd3c4481 100644
--- a/django/db/backends/mysql/base.py
+++ b/django/db/backends/mysql/base.py
@@ -116,30 +116,22 @@ class CursorWrapper(object):
     def execute(self, query, args=None):
         try:
             return self.cursor.execute(query, args)
-        except Database.IntegrityError as e:
-            six.reraise(utils.IntegrityError, utils.IntegrityError(*tuple(e.args)), sys.exc_info()[2])
         except Database.OperationalError as e:
             # Map some error codes to IntegrityError, since they seem to be
             # misclassified and Django would prefer the more logical place.
             if e[0] in self.codes_for_integrityerror:
                 six.reraise(utils.IntegrityError, utils.IntegrityError(*tuple(e.args)), sys.exc_info()[2])
-            six.reraise(utils.DatabaseError, utils.DatabaseError(*tuple(e.args)), sys.exc_info()[2])
-        except Database.DatabaseError as e:
-            six.reraise(utils.DatabaseError, utils.DatabaseError(*tuple(e.args)), sys.exc_info()[2])
+            raise
 
     def executemany(self, query, args):
         try:
             return self.cursor.executemany(query, args)
-        except Database.IntegrityError as e:
-            six.reraise(utils.IntegrityError, utils.IntegrityError(*tuple(e.args)), sys.exc_info()[2])
         except Database.OperationalError as e:
             # Map some error codes to IntegrityError, since they seem to be
             # misclassified and Django would prefer the more logical place.
             if e[0] in self.codes_for_integrityerror:
                 six.reraise(utils.IntegrityError, utils.IntegrityError(*tuple(e.args)), sys.exc_info()[2])
-            six.reraise(utils.DatabaseError, utils.DatabaseError(*tuple(e.args)), sys.exc_info()[2])
-        except Database.DatabaseError as e:
-            six.reraise(utils.DatabaseError, utils.DatabaseError(*tuple(e.args)), sys.exc_info()[2])
+            raise
 
     def __getattr__(self, attr):
         if attr in self.__dict__:
@@ -391,6 +383,8 @@ class DatabaseWrapper(BaseDatabaseWrapper):
         'iendswith': 'LIKE %s',
     }
 
+    Database = Database
+
     def __init__(self, *args, **kwargs):
         super(DatabaseWrapper, self).__init__(*args, **kwargs)
 
diff --git a/django/db/backends/oracle/base.py b/django/db/backends/oracle/base.py
index 3c799f01c1..d35e814d1f 100644
--- a/django/db/backends/oracle/base.py
+++ b/django/db/backends/oracle/base.py
@@ -501,6 +501,8 @@ class DatabaseWrapper(BaseDatabaseWrapper):
         'iendswith': "LIKEC UPPER(%s) ESCAPE '\\'",
     })
 
+    Database = Database
+
     def __init__(self, *args, **kwargs):
         super(DatabaseWrapper, self).__init__(*args, **kwargs)
 
@@ -604,10 +606,6 @@ class DatabaseWrapper(BaseDatabaseWrapper):
         if self.connection is not None:
             try:
                 return self.connection.commit()
-            except Database.IntegrityError as e:
-                # In case cx_Oracle implements (now or in a future version)
-                # raising this specific exception
-                six.reraise(utils.IntegrityError, utils.IntegrityError(*tuple(e.args)), sys.exc_info()[2])
             except Database.DatabaseError as e:
                 # cx_Oracle 5.0.4 raises a cx_Oracle.DatabaseError exception
                 # with the following attributes and values:
@@ -620,7 +618,7 @@ class DatabaseWrapper(BaseDatabaseWrapper):
                 if hasattr(x, 'code') and hasattr(x, 'message') \
                    and x.code == 2091 and 'ORA-02291' in x.message:
                     six.reraise(utils.IntegrityError, utils.IntegrityError(*tuple(e.args)), sys.exc_info()[2])
-                six.reraise(utils.DatabaseError, utils.DatabaseError(*tuple(e.args)), sys.exc_info()[2])
+                raise
 
     @cached_property
     def oracle_version(self):
@@ -760,13 +758,11 @@ class FormatStylePlaceholderCursor(object):
         self._guess_input_sizes([params])
         try:
             return self.cursor.execute(query, self._param_generator(params))
-        except Database.IntegrityError as e:
-            six.reraise(utils.IntegrityError, utils.IntegrityError(*tuple(e.args)), sys.exc_info()[2])
         except Database.DatabaseError as e:
             # cx_Oracle <= 4.4.0 wrongly raises a DatabaseError for ORA-01400.
             if hasattr(e.args[0], 'code') and e.args[0].code == 1400 and not isinstance(e, IntegrityError):
                 six.reraise(utils.IntegrityError, utils.IntegrityError(*tuple(e.args)), sys.exc_info()[2])
-            six.reraise(utils.DatabaseError, utils.DatabaseError(*tuple(e.args)), sys.exc_info()[2])
+            raise
 
     def executemany(self, query, params=None):
         # cx_Oracle doesn't support iterators, convert them to lists
@@ -789,13 +785,11 @@ class FormatStylePlaceholderCursor(object):
         try:
             return self.cursor.executemany(query,
                                 [self._param_generator(p) for p in formatted])
-        except Database.IntegrityError as e:
-            six.reraise(utils.IntegrityError, utils.IntegrityError(*tuple(e.args)), sys.exc_info()[2])
         except Database.DatabaseError as e:
             # cx_Oracle <= 4.4.0 wrongly raises a DatabaseError for ORA-01400.
             if hasattr(e.args[0], 'code') and e.args[0].code == 1400 and not isinstance(e, IntegrityError):
                 six.reraise(utils.IntegrityError, utils.IntegrityError(*tuple(e.args)), sys.exc_info()[2])
-            six.reraise(utils.DatabaseError, utils.DatabaseError(*tuple(e.args)), sys.exc_info()[2])
+            raise
 
     def fetchone(self):
         row = self.cursor.fetchone()
diff --git a/django/db/backends/postgresql_psycopg2/base.py b/django/db/backends/postgresql_psycopg2/base.py
index bf129c0758..fb04072494 100644
--- a/django/db/backends/postgresql_psycopg2/base.py
+++ b/django/db/backends/postgresql_psycopg2/base.py
@@ -40,40 +40,6 @@ def utc_tzinfo_factory(offset):
         raise AssertionError("database connection isn't set to UTC")
     return utc
 
-class CursorWrapper(object):
-    """
-    A thin wrapper around psycopg2's normal cursor class so that we can catch
-    particular exception instances and reraise them with the right types.
-    """
-
-    def __init__(self, cursor):
-        self.cursor = cursor
-
-    def execute(self, query, args=None):
-        try:
-            return self.cursor.execute(query, args)
-        except Database.IntegrityError as e:
-            six.reraise(utils.IntegrityError, utils.IntegrityError(*tuple(e.args)), sys.exc_info()[2])
-        except Database.DatabaseError as e:
-            six.reraise(utils.DatabaseError, utils.DatabaseError(*tuple(e.args)), sys.exc_info()[2])
-
-    def executemany(self, query, args):
-        try:
-            return self.cursor.executemany(query, args)
-        except Database.IntegrityError as e:
-            six.reraise(utils.IntegrityError, utils.IntegrityError(*tuple(e.args)), sys.exc_info()[2])
-        except Database.DatabaseError as e:
-            six.reraise(utils.DatabaseError, utils.DatabaseError(*tuple(e.args)), sys.exc_info()[2])
-
-    def __getattr__(self, attr):
-        if attr in self.__dict__:
-            return self.__dict__[attr]
-        else:
-            return getattr(self.cursor, attr)
-
-    def __iter__(self):
-        return iter(self.cursor)
-
 class DatabaseFeatures(BaseDatabaseFeatures):
     needs_datetime_string_cast = False
     can_return_id_from_insert = True
@@ -106,6 +72,8 @@ class DatabaseWrapper(BaseDatabaseWrapper):
         'iendswith': 'LIKE UPPER(%s)',
     }
 
+    Database = Database
+
     def __init__(self, *args, **kwargs):
         super(DatabaseWrapper, self).__init__(*args, **kwargs)
 
@@ -207,7 +175,7 @@ class DatabaseWrapper(BaseDatabaseWrapper):
     def create_cursor(self):
         cursor = self.connection.cursor()
         cursor.tzinfo_factory = utc_tzinfo_factory if settings.USE_TZ else None
-        return CursorWrapper(cursor)
+        return cursor
 
     def _enter_transaction_management(self, managed):
         """
@@ -245,10 +213,3 @@ class DatabaseWrapper(BaseDatabaseWrapper):
         if ((self.transaction_state and self.transaction_state[-1]) or
                 not self.features.uses_autocommit):
             super(DatabaseWrapper, self).set_dirty()
-
-    def _commit(self):
-        if self.connection is not None:
-            try:
-                return self.connection.commit()
-            except Database.IntegrityError as e:
-                six.reraise(utils.IntegrityError, utils.IntegrityError(*tuple(e.args)), sys.exc_info()[2])
diff --git a/django/db/backends/sqlite3/base.py b/django/db/backends/sqlite3/base.py
index 7ddaaf8fe3..6bf1ffc469 100644
--- a/django/db/backends/sqlite3/base.py
+++ b/django/db/backends/sqlite3/base.py
@@ -10,7 +10,6 @@ import datetime
 import decimal
 import warnings
 import re
-import sys
 
 from django.db import utils
 from django.db.backends import *
@@ -291,6 +290,8 @@ class DatabaseWrapper(BaseDatabaseWrapper):
         'iendswith': "LIKE %s ESCAPE '\\'",
     }
 
+    Database = Database
+
     def __init__(self, *args, **kwargs):
         super(DatabaseWrapper, self).__init__(*args, **kwargs)
 
@@ -398,24 +399,14 @@ class SQLiteCursorWrapper(Database.Cursor):
     """
     def execute(self, query, params=()):
         query = self.convert_query(query)
-        try:
-            return Database.Cursor.execute(self, query, params)
-        except Database.IntegrityError as e:
-            six.reraise(utils.IntegrityError, utils.IntegrityError(*tuple(e.args)), sys.exc_info()[2])
-        except Database.DatabaseError as e:
-            six.reraise(utils.DatabaseError, utils.DatabaseError(*tuple(e.args)), sys.exc_info()[2])
+        return Database.Cursor.execute(self, query, params)
 
     def executemany(self, query, param_list):
         query = self.convert_query(query)
-        try:
-            return Database.Cursor.executemany(self, query, param_list)
-        except Database.IntegrityError as e:
-            six.reraise(utils.IntegrityError, utils.IntegrityError(*tuple(e.args)), sys.exc_info()[2])
-        except Database.DatabaseError as e:
-            six.reraise(utils.DatabaseError, utils.DatabaseError(*tuple(e.args)), sys.exc_info()[2])
+        return Database.Cursor.executemany(self, query, param_list)
 
     def convert_query(self, query):
-        return FORMAT_QMARK_REGEX.sub('?', query).replace('%%','%')
+        return FORMAT_QMARK_REGEX.sub('?', query).replace('%%', '%')
 
 def _sqlite_date_extract(lookup_type, dt):
     if dt is None:
diff --git a/django/db/backends/util.py b/django/db/backends/util.py
index ebab982a04..5eb6626fc7 100644
--- a/django/db/backends/util.py
+++ b/django/db/backends/util.py
@@ -22,7 +22,12 @@ class CursorWrapper(object):
     def __getattr__(self, attr):
         if attr in ('execute', 'executemany', 'callproc'):
             self.db.set_dirty()
-        return getattr(self.cursor, attr)
+        cursor_attr = getattr(self.cursor, attr)
+        if attr in ('callproc', 'close', 'execute', 'executemany',
+                    'fetchone', 'fetchmany', 'fetchall', 'nextset'):
+            return self.db.wrap_database_errors()(cursor_attr)
+        else:
+            return cursor_attr
 
     def __iter__(self):
         return iter(self.cursor)
@@ -34,7 +39,8 @@ class CursorDebugWrapper(CursorWrapper):
         self.db.set_dirty()
         start = time()
         try:
-            return self.cursor.execute(sql, params)
+            with self.db.wrap_database_errors():
+                return self.cursor.execute(sql, params)
         finally:
             stop = time()
             duration = stop - start
@@ -51,7 +57,8 @@ class CursorDebugWrapper(CursorWrapper):
         self.db.set_dirty()
         start = time()
         try:
-            return self.cursor.executemany(sql, param_list)
+            with self.db.wrap_database_errors():
+                return self.cursor.executemany(sql, param_list)
         finally:
             stop = time()
             duration = stop - start
diff --git a/django/db/utils.py b/django/db/utils.py
index 91fa774ed4..c841e06f3e 100644
--- a/django/db/utils.py
+++ b/django/db/utils.py
@@ -1,3 +1,4 @@
+from functools import wraps
 import os
 import pkgutil
 from threading import local
@@ -12,16 +13,87 @@ from django.utils import six
 
 DEFAULT_DB_ALIAS = 'default'
 
-# Define some exceptions that mirror the PEP249 interface.
-# We will rethrow any backend-specific errors using these
-# common wrappers
-class DatabaseError(Exception):
+
+class Error(StandardError):
+    pass
+
+
+class InterfaceError(Error):
+    pass
+
+
+class DatabaseError(Error):
+    pass
+
+
+class DataError(DatabaseError):
+    pass
+
+
+class OperationalError(DatabaseError):
     pass
 
+
 class IntegrityError(DatabaseError):
     pass
 
 
+class InternalError(DatabaseError):
+    pass
+
+
+class ProgrammingError(DatabaseError):
+    pass
+
+
+class NotSupportedError(DatabaseError):
+    pass
+
+
+class DatabaseErrorWrapper(object):
+    """
+    Context manager and decorator that re-throws backend-specific database
+    exceptions using Django's common wrappers.
+    """
+
+    def __init__(self, database):
+        """
+        database is a module defining PEP-249 exceptions.
+        """
+        self.database = database
+
+    def __enter__(self):
+        pass
+
+    def __exit__(self, exc_type, exc_value, traceback):
+        if exc_type is None:
+            return
+        for dj_exc_type in (
+                DataError,
+                OperationalError,
+                IntegrityError,
+                InternalError,
+                ProgrammingError,
+                NotSupportedError,
+                DatabaseError,
+                InterfaceError,
+                Error,
+            ):
+            db_exc_type = getattr(self.database, dj_exc_type.__name__)
+            if issubclass(exc_type, db_exc_type):
+                dj_exc_value = dj_exc_type(*tuple(exc_value.args))
+                if six.PY3:
+                    dj_exc_value.__cause__ = exc_value
+                six.reraise(dj_exc_type, dj_exc_value, traceback)
+
+    def __call__(self, func):
+        @wraps(func)
+        def inner(*args, **kwargs):
+            with self:
+                return func(*args, **kwargs)
+        return inner
+
+
 def load_backend(backend_name):
     # Look for a fully qualified database backend name
     try:
diff --git a/docs/ref/exceptions.txt b/docs/ref/exceptions.txt
index f123ae2e59..93bb9ed251 100644
--- a/docs/ref/exceptions.txt
+++ b/docs/ref/exceptions.txt
@@ -119,18 +119,28 @@ NoReverseMatch
 Database Exceptions
 ===================
 
-Django wraps the standard database exceptions :exc:`DatabaseError` and
-:exc:`IntegrityError` so that your Django code has a guaranteed common
-implementation of these classes. These database exceptions are
-provided in :mod:`django.db`.
+Django wraps the standard database exceptions so that your Django code has a
+guaranteed common implementation of these classes. These database exceptions
+are provided in :mod:`django.db`.
 
+.. exception:: Error
+.. exception:: InterfaceError
 .. exception:: DatabaseError
+.. exception:: DataError
+.. exception:: OperationalError
 .. exception:: IntegrityError
+.. exception:: InternalError
+.. exception:: ProgrammingError
+.. exception:: NotSupportedError
 
 The Django wrappers for database exceptions behave exactly the same as
 the underlying database exceptions. See :pep:`249`, the Python Database API
 Specification v2.0, for further information.
 
+.. versionchanged:: 1.6
+    Previous version of Django only wrapped ``DatabaseError`` and
+    ``IntegrityError``.
+
 .. exception:: models.ProtectedError
 
 Raised to prevent deletion of referenced objects when using
diff --git a/docs/releases/1.6.txt b/docs/releases/1.6.txt
index 1083d4d515..c6a4fb2d5d 100644
--- a/docs/releases/1.6.txt
+++ b/docs/releases/1.6.txt
@@ -60,6 +60,8 @@ Minor features
 * In addition to :lookup:`year`, :lookup:`month` and :lookup:`day`, the ORM
   now supports :lookup:`hour`, :lookup:`minute` and :lookup:`second` lookups.
 
+* Django now wraps all PEP-249 exceptions.
+
 * The default widgets for :class:`~django.forms.EmailField`,
   :class:`~django.forms.URLField`, :class:`~django.forms.IntegerField`,
   :class:`~django.forms.FloatField` and :class:`~django.forms.DecimalField` use