Fix invalid-type error messages

Was always saying that the actual type was a string, which is
wrong.

Author: jamesls

jmespath/functions.py

@@ -317,7 +317,7 @@ def _func_sort_by(self, array, expref):
         # that validates that type, which requires that remaining array
         # elements resolve to the same type as the first element.
         required_type = self._convert_to_jmespath_type(
-            self.interpreter.visit(expref.expression, array[0]))
+            type(self.interpreter.visit(expref.expression, array[0])).__name__)
         if required_type not in ['number', 'string']:
             raise exceptions.JMESPathTypeError(
                 'sort_by', array[0], required_type, ['string', 'number'])
@@ -345,12 +345,14 @@ def _create_key_func(self, expr_node, allowed_types, function_name):
 
         def keyfunc(x):
             result = interpreter.visit(expr_node, x)
-            jmespath_type = self._convert_to_jmespath_type(result)
+            actual_typename = type(result).__name__
+            jmespath_type = self._convert_to_jmespath_type(actual_typename)
+            # allowed_types is in term of jmespath types, not python types.
             if jmespath_type not in allowed_types:
                 raise exceptions.JMESPathTypeError(
                     function_name, result, jmespath_type, allowed_types)
             return result
         return keyfunc
 
     def _convert_to_jmespath_type(self, pyobject):
-        return TYPES_MAP.get(type(pyobject).__name__, 'unknown')
+        return TYPES_MAP.get(pyobject, 'unknown')

tests/test_functions.py

@@ -4,6 +4,7 @@
 import json
 
 import jmespath
+from jmespath.exceptions import JMESPathTypeError
 
 
 class TestFunctions(unittest.TestCase):
@@ -16,3 +17,17 @@ def test_can_max_datetimes(self):
         data = [datetime.now(), datetime.now() + timedelta(seconds=1)]
         result = jmespath.search('max([*].to_string(@))', data)
         self.assertEqual(json.loads(result), str(data[-1]))
+
+    def test_type_error_messages(self):
+        with self.assertRaises(JMESPathTypeError) as e:
+            jmespath.search('length(@)', 2)
+        exception = e.exception
+        # 1. Function name should be in error message
+        self.assertIn('length()', str(exception))
+        # 2. Mention it's an invalid type
+        self.assertIn('invalid type for value: 2', str(exception))
+        # 3. Mention the valid types:
+        self.assertIn("expected one of: ['string', 'array', 'object']",
+                      str(exception))
+        # 4. Mention the actual type.
+        self.assertIn('received: "number"', str(exception))