add overrides.d for settings defaults (#224)

jupyterlab_server/settings_utils.py

@@ -266,26 +266,50 @@ def _path(root_dir, schema_name, make_dirs=False, extension='.json'):
 
     return path
 
-
 def _get_overrides(app_settings_dir):
-    """Get overrides settings from `app_settings_dir`."""
+    """Get overrides settings from `app_settings_dir`.
+
+    The ordering of paths is:
+    - {app_settings_dir}/overrides.d/*.{json,json5} (many, namespaced by package)
+    - {app_settings_dir}/overrides.{json,json5} (singleton, owned by the user)
+    """
     overrides, error = {}, ""
-    overrides_path = os.path.join(app_settings_dir, 'overrides.json')
 
-    if not os.path.exists(overrides_path):
-        overrides_path = os.path.join(app_settings_dir, 'overrides.json5')
+    overrides_d = os.path.join(app_settings_dir, 'overrides.d')
+
+    # find (and sort) the conf.d overrides files
+    all_override_paths = sorted([
+        *(glob(os.path.join(overrides_d, '*.json'))),
+        *(glob(os.path.join(overrides_d, '*.json5'))),
+    ])
+
+    all_override_paths += [
+        os.path.join(app_settings_dir, 'overrides.json'),
+        os.path.join(app_settings_dir, 'overrides.json5')
+    ]
+
+    for overrides_path in all_override_paths:
+        if not os.path.exists(overrides_path):
+            continue
 
-    if os.path.exists(overrides_path):
         with open(overrides_path, encoding='utf-8') as fid:
             try:
-                overrides = json5.load(fid)
+                if overrides_path.endswith('.json5'):
+                    path_overrides = json5.load(fid)
+                else:
+                    path_overrides = json.load(fid)
+                for plugin_id, config in path_overrides.items():
+                    recursive_update(overrides.setdefault(plugin_id, {}), config)
+                print(overrides_path, overrides)
             except Exception as e:
                 error = e
 
     # Allow `default_settings_overrides.json` files in <jupyter_config>/labconfig dirs
     # to allow layering of defaults
     cm = ConfigManager(config_dir_name="labconfig")
-    recursive_update(overrides, cm.get('default_setting_overrides'))
+
+    for plugin_id, config in cm.get('default_setting_overrides').items():
+        recursive_update(overrides.setdefault(plugin_id, {}), config)
 
     return overrides, error
 

jupyterlab_server/tests/test_settings_api.py

@@ -1,8 +1,9 @@
 """Test the Settings service API.
 """
+from pathlib import Path
+import json
 
 import pytest
-import json
 import json5
 import tornado
 
@@ -28,6 +29,28 @@ async def test_get_settings_overrides_dicts(jp_fetch, labserverapp):
     assert len(schema['properties']['codeCellConfig']['default']) == 15
 
 
+@pytest.mark.parametrize('ext', ['json', 'json5'])
+async def test_get_settings_overrides_d_dicts(jp_fetch, labserverapp, ext):
+    # Check that values that are dictionaries in overrides.d/*.json are
+    # merged with the schema.
+    id = '@jupyterlab/apputils-extension:themes'
+    overrides_d = Path(labserverapp.app_settings_dir) / "overrides.d"
+    overrides_d.mkdir(exist_ok=True, parents=True)
+    for i in range(10):
+        text = json.dumps({id: {'codeCellConfig': {'cursorBlinkRate': 530 + i}}})
+        if ext == 'json5':
+            text += '\n// a comment'
+        (overrides_d / f"foo-{i}.{ext}").write_text(text, encoding='utf-8')
+    r = await jp_fetch('lab', 'api', 'settings', id)
+    validate_request(r)
+    res = r.body.decode()
+    data = json.loads(res)
+    assert data['id'] == id
+    schema = data['schema']
+    # Check that the last overrides.d/*.json file is respected.
+    assert schema['properties']['codeCellConfig']['default']['cursorBlinkRate'] == 539
+
+
 async def test_get_settings(jp_fetch, labserverapp):
     id = '@jupyterlab/apputils-extension:themes'
     r = await jp_fetch('lab', 'api', 'settings', id)