Only roll-back in outermost @transaction decorator/ctx manager.

See #2767 for discussion.

docs/peewee/database.rst

@@ -1656,8 +1656,11 @@ block. When this happens, a new transaction will be started.
 .. note::
     If you attempt to nest transactions with peewee using the
     :py:meth:`~Database.transaction` context manager, only the outer-most
-    transaction will be used. However if an exception occurs in a nested block,
-    this can lead to unpredictable behavior, so it is strongly recommended that
+    transaction will be used. If an exception occurs in a nested block, the
+    transaction will NOT be rolled-back -- only exceptions that bubble-up to
+    the outer-most transaction will trigger a rollback.
+
+    As this can may lead to unpredictable behavior, it is recommended that
     you use :py:meth:`~Database.atomic`.
 
 Explicit Savepoints

peewee.py

@@ -4405,10 +4405,11 @@ def __enter__(self):
         return self
 
     def __exit__(self, exc_type, exc_val, exc_tb):
+        depth = self.db.transaction_depth()
         try:
-            if exc_type:
+            if exc_type and depth == 1:
                 self.rollback(False)
-            elif self.db.transaction_depth() == 1:
+            elif depth == 1:
                 try:
                     self.commit(False)
                 except:

tests/transactions.py

@@ -139,6 +139,17 @@ def test_nesting_transaction_obj(self):
 
         self.assertRegister([3, 4, 5])
 
+        with db.transaction() as txn:
+            self._save(6)
+            try:
+                with db.transaction() as txn2:
+                    self._save(7)
+                    raise ValueError()
+            except ValueError:
+                pass
+
+        self.assertRegister([3, 4, 5, 6, 7])
+
     @requires_nested
     def test_savepoint_commit(self):
         with db.atomic() as txn: