Throw if the appservice config list is the wrong type (#15425)

* raise a ConfigError on an invalid app_service_config_files

* changelog

* Move config check to read_config

* Add test

* Ensure list also contains strings

tests/config/test_appservice.py

@@ -0,0 +1,40 @@
+# Copyright 2023 Matrix.org Foundation C.I.C.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from synapse.config.appservice import AppServiceConfig, ConfigError
+
+from tests.unittest import TestCase
+
+
+class AppServiceConfigTest(TestCase):
+    def test_invalid_app_service_config_files(self) -> None:
+        for invalid_value in [
+            "foobar",
+            1,
+            None,
+            True,
+            False,
+            {},
+            ["foo", "bar", False],
+        ]:
+            with self.assertRaises(ConfigError):
+                AppServiceConfig().read_config(
+                    {"app_service_config_files": invalid_value}
+                )
+
+    def test_valid_app_service_config_files(self) -> None:
+        AppServiceConfig().read_config({"app_service_config_files": []})
+        AppServiceConfig().read_config(
+            {"app_service_config_files": ["/not/a/real/path", "/not/a/real/path/2"]}
+        )