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

tests/test_cli.py

@@ -240,6 +240,31 @@ def test_setting(args):
     assert settings["default_page_size"] == 5
 
 
+def test_setting_compatible_with_config(tmp_path):
+    # https://github.com/simonw/datasette/issues/2389
+    runner = CliRunner()
+    config_path = tmp_path / "config.json"
+    config_path.write_text(
+        '{"settings": {"default_page_size": 5, "sql_time_limit_ms": 50}}', "utf-8"
+    )
+    result = runner.invoke(
+        cli,
+        [
+            "--get",
+            "/-/settings.json",
+            "--config",
+            str(config_path),
+            "--setting",
+            "default_page_size",
+            "10",
+        ],
+    )
+    assert result.exit_code == 0, result.output
+    settings = json.loads(result.output)
+    assert settings["default_page_size"] == 10
+    assert settings["sql_time_limit_ms"] == 50
+
+
 def test_plugin_s_overwrite():
     runner = CliRunner()
     plugins_dir = str(pathlib.Path(__file__).parent / "plugins")

tests/test_utils.py

@@ -722,3 +722,35 @@ async def test_calculate_etag(tmp_path):
     utils._etag_cache[path] = "hash"
     assert "hash" == await utils.calculate_etag(path)
     utils._etag_cache.clear()
+
+
+@pytest.mark.parametrize(
+    "dict1,dict2,expected",
+    [
+        # Basic update
+        ({"a": 1, "b": 2}, {"b": 3, "c": 4}, {"a": 1, "b": 3, "c": 4}),
+        # Nested dictionary update
+        (
+            {"a": 1, "b": {"x": 10, "y": 20}},
+            {"b": {"y": 30, "z": 40}},
+            {"a": 1, "b": {"x": 10, "y": 30, "z": 40}},
+        ),
+        # Deep nested update
+        (
+            {"a": {"b": {"c": 1}}},
+            {"a": {"b": {"d": 2}}},
+            {"a": {"b": {"c": 1, "d": 2}}},
+        ),
+        # Update with mixed types
+        (
+            {"a": 1, "b": {"x": 10}},
+            {"b": {"y": 20}, "c": [1, 2, 3]},
+            {"a": 1, "b": {"x": 10, "y": 20}, "c": [1, 2, 3]},
+        ),
+    ],
+)
+def test_deep_dict_update(dict1, dict2, expected):
+    result = utils.deep_dict_update(dict1, dict2)
+    assert result == expected
+    # Check that the original dict1 was modified
+    assert dict1 == expected