Apply JSON config updates recursively

IPython/html/services/config/handlers.py

@@ -9,6 +9,25 b' from tornado import web'
 
 from ...base.handlers import IPythonHandler, json_errors
 
+def recursive_update(target, new):
+    """Recursively update one dictionary using another.
+    
+    None values will delete their keys.
+    """
+    for k, v in new.items():
+        if isinstance(v, dict):
+            if k not in target:
+                target[k] = {}
+            recursive_update(target[k], v)
+            if not target[k]:
+                # Prune empty subdicts
+                del target[k]
+
+        elif v is None:
+            target.pop(k, None)
+
+        else:
+            target[k] = v
 
 class ConfigHandler(IPythonHandler):
     SUPPORTED_METHODS = ('GET', 'PUT', 'PATCH')
@@ -46,11 +65,8 b' class ConfigHandler(IPythonHandler):'
         else:
             section = {}
 
-        for k, v in self.get_json_body().items():
-            if v is None:
-                section.pop(k, None)
-            else:
-                section[k] = v
+        update = self.get_json_body()
+        recursive_update(section, update)
 
         with io.open(filename, 'w', encoding='utf-8') as f:
             json.dump(section, f)

IPython/html/services/config/tests/test_config_api.py

@@ -1,5 +1,5 b''
 # coding: utf-8
-"""Test the kernel specs webservice API."""
+"""Test the config webservice API."""
 
 import json
 
@@ -32,7 +32,7 b' class ConfigAPI(object):'
         return self._req('PATCH', section, json.dumps(values))
 
 class APITest(NotebookTestBase):
-    """Test the kernelspec web service API"""
+    """Test the config web service API"""
     def setUp(self):
         self.config_api = ConfigAPI(self.base_url())
 
@@ -46,18 +46,22 b' class APITest(NotebookTestBase):'
         self.assertEqual(r.json(), sample)
 
     def test_modify(self):
-        sample = {'foo': 'bar', 'baz': 73}
+        sample = {'foo': 'bar', 'baz': 73,
+                  'sub': {'a': 6, 'b': 7}, 'sub2': {'c': 8}}
         self.config_api.set('example', sample)
 
         r = self.config_api.modify('example', {'foo': None,  # should delete foo
                                                'baz': 75,
                                                'wib': [1,2,3],
+                                               'sub': {'a': 8, 'b': None, 'd': 9},
+                                               'sub2': {'c': None}  # should delete sub2
                                               })
         self.assertEqual(r.status_code, 204)
 
         r = self.config_api.get('example')
         self.assertEqual(r.status_code, 200)
-        self.assertEqual(r.json(), {'baz': 75, 'wib': [1,2,3]})
+        self.assertEqual(r.json(), {'baz': 75, 'wib': [1,2,3],
+                                    'sub': {'a': 8, 'd': 9}})
 
     def test_get_unknown(self):
         # We should get an empty config dictionary instead of a 404