Update JSON schema. (#5982)

* Update JSON schema for pseudo huber.
* Update JSON model schema.

doc/model.schema

@@ -177,6 +177,17 @@
         }
       }
     },
+    "aft_loss_param": {
+      "type": "object",
+      "properties": {
+        "aft_loss_distribution": {
+          "type": "string"
+        },
+        "aft_loss_distribution_scale": {
+          "type": "string"
+        }
+      }
+    },
     "softmax_multiclass_param": {
       "type": "object",
       "properties": {
@@ -273,6 +284,17 @@
                 "reg_loss_param"
               ]
             },
+            {
+              "type": "object",
+              "properties": {
+                "name": { "const": "reg:pseudohubererror" },
+                "reg_loss_param": { "$ref": "#/definitions/reg_loss_param"}
+              },
+              "required": [
+                "name",
+                "reg_loss_param"
+              ]
+            },
             {
               "type": "object",
               "properties": {
@@ -284,6 +306,17 @@
                 "reg_loss_param"
               ]
             },
+            {
+              "type": "object",
+              "properties": {
+                "name": { "const": "reg:linear" },
+                "reg_loss_param": { "$ref": "#/definitions/reg_loss_param"}
+              },
+              "required": [
+                "name",
+                "reg_loss_param"
+              ]
+            },
             {
               "type": "object",
               "properties": {
@@ -420,6 +453,19 @@
                 "name",
                 "lambda_rank_param"
               ]
+            },
+            {
+              "type": "object",
+              "properties": {
+                "name": {"const": "survival:aft"},
+                "aft_loss_param": { "$ref": "#/definitions/aft_loss_param"}
+              }
+            },
+            {
+              "type": "object",
+              "properties": {
+                "name": {"const": "binary:hinge"}
+              }
             }
           ]
         },

tests/python/test_basic_models.py

@@ -346,6 +346,25 @@ class TestModels(unittest.TestCase):
                             schema=schema)
         os.remove(model_path)
 
+        try:
+            xgb.train({'objective': 'foo'}, dtrain, num_boost_round=1)
+        except ValueError as e:
+            e_str = str(e)
+            beg = e_str.find('Objective candidate')
+            end = e_str.find('Stack trace')
+            e_str = e_str[beg: end]
+            e_str = e_str.strip()
+            splited = e_str.splitlines()
+            objectives = [s.split(': ')[1] for s in splited]
+            j_objectives = schema['properties']['learner']['properties'][
+                'objective']['oneOf']
+            objectives_from_schema = set()
+            for j_obj in j_objectives:
+                objectives_from_schema.add(
+                    j_obj['properties']['name']['const'])
+            objectives = set(objectives)
+            assert objectives == objectives_from_schema
+
     @pytest.mark.skipif(**tm.no_json_schema())
     def test_json_dump_schema(self):
         import jsonschema