[1.6.x] Introduced getters for connection.autocommit and .needs_rollback.

They ensure that the attributes aren't accessed in conditions where they
don't contain a valid value.

Fixed #20666.

Backport of dd9c6bc359 from master.

django/db/backends/__init__.py

@@ -204,7 +204,7 @@ class BaseDatabaseWrapper(object):
 
     def _savepoint_allowed(self):
         # Savepoints cannot be created outside a transaction
-        return self.features.uses_savepoints and not self.autocommit
+        return self.features.uses_savepoints and not self.get_autocommit()
 
     ##### Generic savepoint management methods #####
 
@@ -279,15 +279,13 @@ class BaseDatabaseWrapper(object):
         """
         self.validate_no_atomic_block()
 
-        self.ensure_connection()
-
         self.transaction_state.append(managed)
 
         if not managed and self.is_dirty() and not forced:
             self.commit()
             self.set_clean()
 
-        if managed == self.autocommit:
+        if managed == self.get_autocommit():
             self.set_autocommit(not managed)
 
     def leave_transaction_management(self):
@@ -298,8 +296,6 @@ class BaseDatabaseWrapper(object):
         """
         self.validate_no_atomic_block()
 
-        self.ensure_connection()
-
         if self.transaction_state:
             del self.transaction_state[-1]
         else:
@@ -313,14 +309,21 @@ class BaseDatabaseWrapper(object):
 
         if self._dirty:
             self.rollback()
-            if managed == self.autocommit:
+            if managed == self.get_autocommit():
                 self.set_autocommit(not managed)
             raise TransactionManagementError(
                 "Transaction managed block ended with pending COMMIT/ROLLBACK")
 
-        if managed == self.autocommit:
+        if managed == self.get_autocommit():
             self.set_autocommit(not managed)
 
+    def get_autocommit(self):
+        """
+        Check the autocommit state.
+        """
+        self.ensure_connection()
+        return self.autocommit
+
     def set_autocommit(self, autocommit):
         """
         Enable or disable autocommit.
@@ -330,13 +333,22 @@ class BaseDatabaseWrapper(object):
         self._set_autocommit(autocommit)
         self.autocommit = autocommit
 
+    def get_rollback(self):
+        """
+        Get the "needs rollback" flag -- for *advanced use* only.
+        """
+        if not self.in_atomic_block:
+            raise TransactionManagementError(
+                "The rollback flag doesn't work outside of an 'atomic' block.")
+        return self.needs_rollback
+
     def set_rollback(self, rollback):
         """
         Set or unset the "needs rollback" flag -- for *advanced use* only.
         """
         if not self.in_atomic_block:
             raise TransactionManagementError(
-                "needs_rollback doesn't work outside of an 'atomic' block.")
+                "The rollback flag doesn't work outside of an 'atomic' block.")
         self.needs_rollback = rollback
 
     def validate_no_atomic_block(self):
@@ -370,7 +382,7 @@ class BaseDatabaseWrapper(object):
         to decide in a managed block of code to decide whether there are open
         changes waiting for commit.
         """
-        if not self.autocommit:
+        if not self.get_autocommit():
             self._dirty = True
 
     def set_clean(self):
@@ -436,7 +448,7 @@ class BaseDatabaseWrapper(object):
         if self.connection is not None:
             # If the application didn't restore the original autocommit setting,
             # don't take chances, drop the connection.
-            if self.autocommit != self.settings_dict['AUTOCOMMIT']:
+            if self.get_autocommit() != self.settings_dict['AUTOCOMMIT']:
                 self.close()
                 return
 

django/db/transaction.py

@@ -123,7 +123,7 @@ def get_autocommit(using=None):
     """
     Get the autocommit status of the connection.
     """
-    return get_connection(using).autocommit
+    return get_connection(using).get_autocommit()
 
 def set_autocommit(autocommit, using=None):
     """
@@ -175,7 +175,7 @@ def get_rollback(using=None):
     """
     Gets the "needs rollback" flag -- for *advanced use* only.
     """
-    return get_connection(using).needs_rollback
+    return get_connection(using).get_rollback()
 
 def set_rollback(rollback, using=None):
     """
@@ -229,15 +229,11 @@ class Atomic(object):
     def __enter__(self):
         connection = get_connection(self.using)
 
-        # Ensure we have a connection to the database before testing
-        # autocommit status.
-        connection.ensure_connection()
-
         if not connection.in_atomic_block:
             # Reset state when entering an outermost atomic block.
             connection.commit_on_exit = True
             connection.needs_rollback = False
-            if not connection.autocommit:
+            if not connection.get_autocommit():
                 # Some database adapters (namely sqlite3) don't handle
                 # transactions and savepoints properly when autocommit is off.
                 # Turning autocommit back on isn't an option; it would trigger
@@ -500,7 +496,7 @@ def commit_on_success_unless_managed(using=None, savepoint=False):
     legacy behavior.
     """
     connection = get_connection(using)
-    if connection.autocommit or connection.in_atomic_block:
+    if connection.get_autocommit() or connection.in_atomic_block:
         return atomic(using, savepoint)
     else:
         def entering(using):