Chore!: Make default_connection optional (#4522)

Author: VaggelisD

sqlmesh/core/config/root.py

@@ -122,7 +122,7 @@ class Config(BaseConfig):
     """
 
     gateways: GatewayDict = {"": GatewayConfig()}
-    default_connection: SerializableConnectionConfig = DuckDBConnectionConfig()
+    default_connection: t.Optional[SerializableConnectionConfig] = None
     default_test_connection_: t.Optional[SerializableConnectionConfig] = Field(
         default=None, alias="default_test_connection"
     )
@@ -280,7 +280,11 @@ def get_gateway(self, name: t.Optional[str] = None) -> GatewayConfig:
         return self.gateways
 
     def get_connection(self, gateway_name: t.Optional[str] = None) -> ConnectionConfig:
-        return self.get_gateway(gateway_name).connection or self.default_connection
+        connection = self.get_gateway(gateway_name).connection or self.default_connection
+        if connection is None:
+            msg = f" for gateway '{gateway_name}'" if gateway_name else ""
+            raise ConfigError(f"No connection configured{msg}.")
+        return connection
 
     def get_state_connection(
         self, gateway_name: t.Optional[str] = None

tests/conftest.py

@@ -1,9 +1,11 @@
 from __future__ import annotations
 
+
 import datetime
 import logging
 import typing as t
 import uuid
+from contextlib import nullcontext
 from pathlib import Path
 from shutil import copytree, rmtree
 from tempfile import TemporaryDirectory
@@ -21,7 +23,8 @@
 from sqlglot.helper import ensure_list
 from sqlglot.optimizer.normalize_identifiers import normalize_identifiers
 
-from sqlmesh.core.config import BaseDuckDBConnectionConfig
+from sqlmesh.core.config import Config, BaseDuckDBConnectionConfig, DuckDBConnectionConfig
+from sqlmesh.core.config.connection import ConnectionConfig
 from sqlmesh.core.context import Context
 from sqlmesh.core.engine_adapter import MSSQLEngineAdapter, SparkEngineAdapter
 from sqlmesh.core.engine_adapter.base import EngineAdapter
@@ -526,3 +529,26 @@ def _make_function(table_name: str, random_id: str) -> exp.Table:
         return temp_table
 
     return _make_function
+
+
+@pytest.fixture(scope="function", autouse=True)
+def set_default_connection(request):
+    request = request.node.get_closest_marker("set_default_connection")
+    disable = request and request.kwargs.get("disable")
+
+    if disable:
+        ctx = nullcontext()
+    else:
+        original_get_connection = Config.get_connection
+
+        def _lax_get_connection(self, gateway_name: t.Optional[str] = None) -> ConnectionConfig:
+            try:
+                connection = original_get_connection(self, gateway_name)
+            except:
+                connection = DuckDBConnectionConfig()
+            return connection
+
+        ctx = mock.patch("sqlmesh.core.config.Config.get_connection", _lax_get_connection)
+
+    with ctx:
+        yield

tests/core/test_integration.py

@@ -64,7 +64,7 @@
     SnapshotTableInfo,
 )
 from sqlmesh.utils.date import TimeLike, now, to_date, to_datetime, to_timestamp
-from sqlmesh.utils.errors import NoChangesPlanError, SQLMeshError, PlanError
+from sqlmesh.utils.errors import NoChangesPlanError, SQLMeshError, PlanError, ConfigError
 from sqlmesh.utils.pydantic import validate_string
 from tests.conftest import DuckDBMetadata, SushiDataValidator
 from tests.utils.test_helpers import use_terminal_console
@@ -6129,3 +6129,22 @@ def setup_senario(model_before: str, model_after: str):
         'Binder Error: Referenced column "this_col_does_not_exist" not found in \nFROM clause!'
         in output.stdout
     )
+
+
+@pytest.mark.set_default_connection(disable=True)
+def test_missing_connection_config():
+    # This is testing the actual implementation of Config.get_connection
+    # To make writing tests easier, it's patched by the autouse fixture provide_sqlmesh_default_connection
+    # Case 1: No default_connection or gateways specified should raise a ConfigError
+    with pytest.raises(ConfigError):
+        ctx = Context(config=Config())
+
+    # Case 2: No connection specified in the gateway should raise a ConfigError
+    with pytest.raises(ConfigError):
+        ctx = Context(config=Config(gateways={"incorrect": GatewayConfig()}))
+
+    # Case 3: Specifying a default_connection or connection in the gateway should work
+    ctx = Context(config=Config(default_connection=DuckDBConnectionConfig()))
+    ctx = Context(
+        config=Config(gateways={"default": GatewayConfig(connection=DuckDBConnectionConfig())})
+    )