Can access positional only and keyword only argument type comments

4 files changed, 89 insertions, 0 deletions

diff --git a/ChangeLog b/ChangeLog
index c54d321a..3949fe26 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -106,6 +106,12 @@ Release Date: TBA
 
   Close PyCQA/pylint#3274
 
+* Can access per argument type comments for positional only and keyword only arguments.
+
+  The comments are accessed through through the new
+  ``Arguments.type_comment_posonlyargs`` and
+  ``Arguments.type_comment_kwonlyargs`` attributes respectively.
+
 What's New in astroid 2.3.2?
 ============================
 Release Date: TBA
diff --git a/astroid/node_classes.py b/astroid/node_classes.py
index b1344723..c57f5686 100644
--- a/astroid/node_classes.py
+++ b/astroid/node_classes.py
@@ -1407,6 +1407,8 @@ class Arguments(mixins.AssignTypeMixin, NodeNG):
         "kwargannotation",
         "kwonlyargs_annotations",
         "type_comment_args",
+        "type_comment_kwonlyargs",
+        "type_comment_posonlyargs",
     )
     varargannotation = None
     """The type annotation for the variable length arguments.
@@ -1502,6 +1504,24 @@ class Arguments(mixins.AssignTypeMixin, NodeNG):
         :type: list(NodeNG or None)
         """
 
+        self.type_comment_kwonlyargs = []
+        """The type annotation, passed by a type comment, of each keyword only argument.
+
+        If an argument does not have a type comment,
+        the value for that argument will be None.
+
+        :type: list(NodeNG or None)
+        """
+
+        self.type_comment_posonlyargs = []
+        """The type annotation, passed by a type comment, of each positional argument.
+
+        If an argument does not have a type comment,
+        the value for that argument will be None.
+
+        :type: list(NodeNG or None)
+        """
+
     # pylint: disable=too-many-arguments
     def postinit(
         self,
@@ -1516,6 +1536,8 @@ class Arguments(mixins.AssignTypeMixin, NodeNG):
         varargannotation=None,
         kwargannotation=None,
         type_comment_args=None,
+        type_comment_kwonlyargs=None,
+        type_comment_posonlyargs=None,
     ):
         """Do some setup after initialisation.
 
@@ -1563,6 +1585,14 @@ class Arguments(mixins.AssignTypeMixin, NodeNG):
         :param type_comment_args: The type annotation,
             passed by a type comment, of each argument.
         :type type_comment_args: list(NodeNG or None)
+
+        :param type_comment_args: The type annotation,
+            passed by a type comment, of each keyword only argument.
+        :type type_comment_args: list(NodeNG or None)
+
+        :param type_comment_args: The type annotation,
+            passed by a type comment, of each positional argument.
+        :type type_comment_args: list(NodeNG or None)
         """
         self.args = args
         self.defaults = defaults
@@ -1575,6 +1605,8 @@ class Arguments(mixins.AssignTypeMixin, NodeNG):
         self.varargannotation = varargannotation
         self.kwargannotation = kwargannotation
         self.type_comment_args = type_comment_args
+        self.type_comment_kwonlyargs = type_comment_kwonlyargs
+        self.type_comment_posonlyargs = type_comment_posonlyargs
 
     # pylint: disable=too-many-arguments
 
diff --git a/astroid/rebuilder.py b/astroid/rebuilder.py
index 10fd5900..6cb36f67 100644
--- a/astroid/rebuilder.py
+++ b/astroid/rebuilder.py
@@ -221,6 +221,14 @@ class TreeRebuilder:
         type_comment_args = [
             self.check_type_comment(child, parent=newnode) for child in node.args
         ]
+        type_comment_kwonlyargs = [
+            self.check_type_comment(child, parent=newnode) for child in node.kwonlyargs
+        ]
+        if PY38:
+            type_comment_posonlyargs = [
+                self.check_type_comment(child, parent=newnode)
+                for child in node.posonlyargs
+            ]
 
         newnode.postinit(
             args=args,
@@ -234,6 +242,8 @@ class TreeRebuilder:
             varargannotation=varargannotation,
             kwargannotation=kwargannotation,
             type_comment_args=type_comment_args,
+            type_comment_kwonlyargs=type_comment_kwonlyargs,
+            type_comment_posonlyargs=type_comment_posonlyargs,
         )
         # save argument names in locals:
         if vararg:
diff --git a/tests/unittest_nodes.py b/tests/unittest_nodes.py
index 5fbef628..78c8cfb2 100644
--- a/tests/unittest_nodes.py
+++ b/tests/unittest_nodes.py
@@ -1131,6 +1131,47 @@ def test_type_comments_arguments():
             assert actual_arg.as_string() == expected_arg
 
 
+@pytest.mark.skipif(
+    not PY38, reason="needs to be able to parse positional only arguments"
+)
+def test_type_comments_posonly_arguments():
+    module = builder.parse(
+        """
+    def f_arg_comment(
+        a,  # type: int
+        b,  # type: int
+        /,
+        c,  # type: Optional[int]
+        d,  # type: Optional[int]
+        *,
+        e,  # type: float
+        f,  # type: float
+    ):
+        # type: (...) -> None
+        pass
+    """
+    )
+    expected_annotations = [
+        [["int", "int"], ["Optional[int]", "Optional[int]"], ["float", "float"]]
+    ]
+    for node, expected_types in zip(module.body, expected_annotations):
+        assert len(node.type_comment_args) == 1
+        if PY38:
+            assert isinstance(node.type_comment_args[0], astroid.Const)
+            assert node.type_comment_args[0].value == Ellipsis
+        else:
+            assert isinstance(node.type_comment_args[0], astroid.Ellipsis)
+        type_comments = [
+            node.args.type_comment_posonlyargs,
+            node.args.type_comment_args,
+            node.args.type_comment_kwonlyargs,
+        ]
+        for expected_args, actual_args in zip(expected_types, type_comments):
+            assert len(expected_args) == len(actual_args)
+            for expected_arg, actual_arg in zip(expected_args, actual_args):
+                assert actual_arg.as_string() == expected_arg
+
+
 def test_is_generator_for_yield_assignments():
     node = astroid.extract_node(
         """