fix #302, check transaction state before rollback

running rollback on failed or already rolled back transactions has no
effect and asyncpg would throw exceptions

Author: wwwjfy

gino/dialects/asyncpg.py

@@ -3,6 +3,7 @@
 import time
 
 import asyncpg
+from asyncpg.transaction import TransactionState
 from sqlalchemy import util, exc, sql
 from sqlalchemy.dialects.postgresql import (  # noqa: F401
     ARRAY,
@@ -242,6 +243,10 @@ async def commit(self):
         await self._tx.commit()
 
     async def rollback(self):
+        # noinspection PyProtectedMember
+        if self._tx._state in (TransactionState.FAILED,
+                               TransactionState.ROLLEDBACK):
+            return
         await self._tx.rollback()
 
 

gino/transaction.py

@@ -166,16 +166,16 @@ async def __aenter__(self):
         return self
 
     async def __aexit__(self, ex_type, ex, ex_tb):
-        try:
-            is_break = ex_type is _Break
-            if is_break and ex.commit:
-                ex_type = None
-            if ex_type is None:
+        is_break = ex_type is _Break
+        if is_break and ex.commit:
+            ex_type = None
+        if ex_type is None:
+            try:
                 await self._tx.commit()
-            else:
+            except Exception:
                 await self._tx.rollback()
-        except Exception:
+                raise
+        else:
             await self._tx.rollback()
-            raise
         if is_break and ex.tx is self:
             return True

tests/test_transaction.py

@@ -1,4 +1,5 @@
 import pytest
+from asyncpg.transaction import TransactionState
 
 from .models import db, User, qsize
 
@@ -249,3 +250,12 @@ async def test_base_exception(engine):
         except Exception:
             assert False, 'Should not reach here'
         assert False, 'Should not reach here'
+
+
+async def test_rollback_failed_transaction(engine):
+    # for transaction whose state is rolled back or failed, rollback() won't
+    # have any effect and shouldn't throw exceptions
+    for state in (TransactionState.ROLLEDBACK, TransactionState.FAILED):
+        async with engine.transaction() as tx:
+            tx._tx._tx._state = state
+            tx.raise_rollback()