Eagerly establish TCP connection in async dialect

Call await_only(raw_conn.connect()) during connect() so connection
errors surface at connect-time rather than on the first query, matching
the pattern used by SQLAlchemy's aiosqlite dialect.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: antoineleclair

src/sqlalchemydqlite/aio.py

@@ -146,8 +146,13 @@ def import_dbapi(cls) -> Any:
         return aio
 
     def connect(self, *cargs: Any, **cparams: Any) -> Any:
-        """Create and wrap an async connection."""
+        """Create and wrap an async connection.
+
+        Eagerly establishes the TCP connection so errors surface at
+        connect-time rather than on the first query.
+        """
         raw_conn = self.loaded_dbapi.connect(*cargs, **cparams)
+        await_only(raw_conn.connect())
         return AsyncAdaptedConnection(raw_conn)
 
     def get_driver_connection(self, connection: Any) -> Any:

tests/test_dialect.py

@@ -392,6 +392,36 @@ def test_sync_dialect_does_not_use_nullpool(self) -> None:
         )
 
 
+class TestAsyncConnect:
+    def test_connect_calls_await_only_on_raw_connect(self) -> None:
+        """Async dialect connect() should eagerly establish the TCP connection."""
+        import ast
+        import inspect
+        import textwrap
+
+        from sqlalchemydqlite.aio import DqliteDialect_aio
+
+        source = textwrap.dedent(inspect.getsource(DqliteDialect_aio.connect))
+        tree = ast.parse(source)
+
+        # Look for await_only(raw_conn.connect()) or similar eager connect call
+        has_eager_connect = False
+        for node in ast.walk(tree):
+            if isinstance(node, ast.Call):
+                func = node.func
+                if isinstance(func, ast.Name) and func.id == "await_only" and node.args:
+                    arg = node.args[0]
+                    if isinstance(arg, ast.Call):
+                        inner = arg.func
+                        if isinstance(inner, ast.Attribute) and inner.attr == "connect":
+                            has_eager_connect = True
+
+        assert has_eager_connect, (
+            "DqliteDialect_aio.connect() should eagerly establish TCP with "
+            "await_only(raw_conn.connect())"
+        )
+
+
 class TestURLParsing:
     def test_parse_basic_url(self) -> None:
         url = URL.create("dqlite", host="localhost", port=9001, database="test")