Handle "required" keyword.

hc/lib/jsonschema.py

@@ -47,10 +47,15 @@ def validate(obj, schema, obj_name="value"):
         if not isinstance(obj, dict):
             raise ValidationError("%s is not an object" % obj_name)
 
-        for key, spec in schema["properties"].items():
+        properties = schema.get("properties", {})
+        for key, spec in properties.items():
             if key in obj:
                 validate(obj[key], spec, obj_name=key)
 
+        for key in schema.get("required", []):
+            if key not in obj:
+                raise ValidationError("key %s absent in %s" % (key, obj_name))
+
     if "enum" in schema:
         if obj not in schema["enum"]:
             raise ValidationError("%s has unexpected value" % obj_name)

hc/lib/tests/test_jsonschema.py

@@ -52,6 +52,13 @@ class JsonSchemaTestCase(TestCase):
                 }
             })
 
+    def test_it_handles_required_properties(self):
+        with self.assertRaises(ValidationError):
+            validate({"foo": "bar"}, {
+                "type": "object",
+                "required": ["baz"]
+            })
+
     def test_it_validates_arrays(self):
         validate(["foo", "bar"], {
             "type": "array",