Partially port PyMySQL/PyMySQL#304

aiomysql now reraises the original exception during connect() if it's not `IOError`, `OSError` or `asyncio.TimeoutError`.
This was previously always raised as `OperationalError`.

fixes #792

CHANGES.txt

@@ -8,6 +8,10 @@ next (unreleased)
 
 * Remove deprecated Pool.get #706
 
+* | Partially ported `PyMySQL#304 <https://github.com/PyMySQL/PyMySQL/pull/304>`_ #792
+  | aiomysql now reraises the original exception during connect() if it's not `IOError`, `OSError` or `asyncio.TimeoutError`.
+  | This was previously always raised as `OperationalError`.
+
 0.1.1 (2022-05-08)
 ^^^^^^^^^^^^^^^^^^
 

aiomysql/connection.py

@@ -555,9 +555,20 @@ async def _connect(self):
                 self._writer.transport.close()
             self._reader = None
             self._writer = None
-            raise OperationalError(2003,
-                                   "Can't connect to MySQL server on %r" %
-                                   self._host) from e
+
+            # As of 3.11, asyncio.TimeoutError is a deprecated alias of
+            # OSError. For consistency, we're also considering this an
+            # OperationalError on earlier python versions.
+            if isinstance(e, (IOError, OSError, asyncio.TimeoutError)):
+                raise OperationalError(
+                    CR.CR_CONN_HOST_ERROR,
+                    "Can't connect to MySQL server on %r" % self._host,
+                ) from e
+
+            # If e is neither IOError nor OSError, it's a bug.
+            # Raising AssertionError would hide the original error, so we just
+            # reraise it.
+            raise
 
     def _set_keep_alive(self):
         transport = self._writer.transport

tests/test_connection.py

@@ -26,7 +26,8 @@ def fill_my_cnf(mysql_params):
 
 @pytest.mark.run_loop
 async def test_connect_timeout(connection_creator):
-    # All exceptions are caught and raised as operational errors
+    # OSErrors and asyncio.TimeoutError are caught and raised as operational
+    # errors
     with pytest.raises(aiomysql.OperationalError):
         await connection_creator(connect_timeout=0.000000000001)
 

tests/test_issues.py

@@ -465,3 +465,13 @@ async def test_issue_323(mysql_server, loop, recwarn):
             finally:
                 async with conn.cursor() as cur:
                     await cur.execute("DELETE FROM `bugtest`.`testtable`;")
+
+
+# https://github.com/aio-libs/aiomysql/issues/792
+@pytest.mark.run_loop
+async def test_issue_792(connection_creator):
+    with pytest.raises(aiomysql.OperationalError) as exc_info:
+        await connection_creator(db="does_not_exist")
+
+    assert exc_info.value.args[0] == 1049
+    assert exc_info.value.args[1] == "Unknown database 'does_not_exist'"