Fix Arguments.arguments so it actually returns all arguments

Closes #2213.

Arguments.arguments() has been modified so that it returns all arguments
as it should (according to its own doc). A test case was also added to
verify this.

Author: crazybolillo

astroid/nodes/node_classes.py

@@ -780,7 +780,18 @@ def fromlineno(self) -> int:
     @cached_property
     def arguments(self):
         """Get all the arguments for this node, including positional only and positional and keyword"""
-        return list(itertools.chain((self.posonlyargs or ()), self.args or ()))
+        retval = list(itertools.chain((self.posonlyargs or ()), (self.args or ())))
+        if self.vararg:
+            retval.append(
+                Name(self.vararg, -1, -1, self, end_lineno=None, end_col_offset=None)
+            )
+        retval += self.kwonlyargs or ()
+        if self.kwarg:
+            retval.append(
+                Name(self.kwarg, -1, -1, self, end_lineno=None, end_col_offset=None)
+            )
+
+        return retval
 
     def format_args(self, *, skippable_names: set[str] | None = None) -> str:
         """Get the arguments formatted as string.
@@ -910,7 +921,9 @@ def default_value(self, argname):
         :raises NoDefault: If there is no default value defined for the
             given argument.
         """
-        args = self.arguments
+        args = list(
+            filter(lambda x: not isinstance(x, Name), self.arguments)
+        )  # Ignore *args and **kwargs
         index = _find_arg(argname, args)[0]
         if index is not None:
             idx = index - (len(args) - len(self.defaults))
@@ -955,7 +968,9 @@ def find_argname(self, argname, rec=DEPRECATED_ARGUMENT_DEFAULT):
                 stacklevel=2,
             )
         if self.arguments:
-            return _find_arg(argname, self.arguments)
+            index, argument = _find_arg(argname, self.arguments)
+            if not isinstance(argument, Name):
+                return index, argument
         return None, None
 
     def get_children(self):

astroid/nodes/scoped_nodes/scoped_nodes.py

@@ -963,11 +963,7 @@ def argnames(self) -> list[str]:
             names = [elt.name for elt in self.args.arguments]
         else:
             names = []
-        if self.args.vararg:
-            names.append(self.args.vararg)
-        names += [elt.name for elt in self.args.kwonlyargs]
-        if self.args.kwarg:
-            names.append(self.args.kwarg)
+
         return names
 
     def infer_call_result(
@@ -1280,11 +1276,7 @@ def argnames(self) -> list[str]:
             names = [elt.name for elt in self.args.arguments]
         else:
             names = []
-        if self.args.vararg:
-            names.append(self.args.vararg)
-        names += [elt.name for elt in self.args.kwonlyargs]
-        if self.args.kwarg:
-            names.append(self.args.kwarg)
+
         return names
 
     def getattr(

tests/test_nodes.py

@@ -22,6 +22,7 @@
     Uninferable,
     bases,
     builder,
+    extract_node,
     nodes,
     parse,
     test_utils,
@@ -1943,3 +1944,28 @@ def test_str_repr_no_warnings(node):
     test_node = node(**args)
     str(test_node)
     repr(test_node)
+
+
+def test_arguments_contains_all():
+    """Ensure Arguments.arguments actually returns all available arguments"""
+
+    def manually_get_args(arg_node) -> set:
+        names = set()
+        if arg_node.args.vararg:
+            names.add(arg_node.args.vararg)
+        if arg_node.args.kwarg:
+            names.add(arg_node.args.kwarg)
+
+        names.update([x.name for x in arg_node.args.args])
+        names.update([x.name for x in arg_node.args.kwonlyargs])
+
+        return names
+
+    node = extract_node("""def a(fruit: str, *args, b=None, c=None, **kwargs): ...""")
+    assert manually_get_args(node) == {x.name for x in node.args.arguments}
+
+    node = extract_node("""def a(mango: int, b="banana", c=None, **kwargs): ...""")
+    assert manually_get_args(node) == {x.name for x in node.args.arguments}
+
+    node = extract_node("""def a(self, num = 10, *args): ...""")
+    assert manually_get_args(node) == {x.name for x in node.args.arguments}