fix default_value for kwonlyargs with no default

Refs #2213.

Requesting the default value for a kwonlyarg with no default would fail with
an IndexError, it now correctly raises a NoDefault exception. This issue
arised after changes in PR #2240.

Author: crazybolillo

astroid/nodes/node_classes.py

@@ -947,8 +947,11 @@ def default_value(self, argname):
         ]
 
         index = _find_arg(argname, self.kwonlyargs)[0]
-        if index is not None and self.kw_defaults[index] is not None:
-            return self.kw_defaults[index]
+        if (index is not None) and (len(self.kw_defaults) > index):
+            if self.kw_defaults[index] is not None:
+                return self.kw_defaults[index]
+            else:
+                raise NoDefault(func=self.parent, name=argname)
 
         index = _find_arg(argname, args)[0]
         if index is not None:

tests/test_inference.py

@@ -38,7 +38,7 @@
     AstroidTypeError,
     AttributeInferenceError,
     InferenceError,
-    NotFoundError,
+    NotFoundError, NoDefault,
 )
 from astroid.objects import ExceptionInstance
 
@@ -146,6 +146,19 @@ def meth3(self, d=attr):
 
     ast = parse(CODE, __name__)
 
+    def test_arg_keyword_no_default_value(self):
+        node = extract_node("""
+        class Sensor:
+            def __init__(self, *, description): #@
+                self._id = description.key
+        """)
+        with self.assertRaises(NoDefault):
+            node.args.default_value("description")
+
+        node = extract_node("def apple(color, *args, name: str, **kwargs): ...")
+        with self.assertRaises(NoDefault):
+            node.args.default_value("name")
+
     def test_infer_abstract_property_return_values(self) -> None:
         module = parse(
             """