Fix bug where -s could reset settings to defaults, closes #2389

datasette/cli.py

@@ -25,6 +25,7 @@ from .utils import (
     LoadExtension,
     StartupError,
     check_connection,
+    deep_dict_update,
     find_spatialite,
     parse_metadata,
     ConnectionProblem,
@@ -552,7 +553,9 @@ def serve(
     # Merge in settings from -s/--setting
     if settings:
         settings_updates = pairs_to_nested_config(settings)
-        config_data.update(settings_updates)
+        # Merge recursively, to avoid over-writing nested values
+        # https://github.com/simonw/datasette/issues/2389
+        deep_dict_update(config_data, settings_updates)
 
     kwargs = dict(
         immutables=immutable,

datasette/utils/__init__.py

@@ -1451,3 +1451,12 @@ async def calculate_etag(filepath, chunk_size=4096):
     _etag_cache[filepath] = etag
 
     return etag
+
+
+def deep_dict_update(dict1, dict2):
+    for key, value in dict2.items():
+        if isinstance(value, dict):
+            dict1[key] = deep_dict_update(dict1.get(key, type(value)()), value)
+        else:
+            dict1[key] = value
+    return dict1