fix: Fix attribute parser for Python 3.9

It seems `ast` has changed in Python 3.9.
Some objects who previously had a `value` attribute
don't have it anymore.

Issue #73: #73
Issue #75: #75

src/pytkdocs/parsers/attributes.py

@@ -16,7 +16,12 @@ def node_to_annotation(node) -> Union[str, object]:
         elif isinstance(node.annotation, (ast.Constant, ast.Str)):
             return node.annotation.s
         elif isinstance(node.annotation, ast.Subscript):
-            return f"{node.annotation.value.id}[{node_to_annotation(node.annotation.slice.value)}]"  # type: ignore
+            value_id = node.annotation.value.id  # type: ignore
+            if hasattr(node.annotation.slice, "value"):
+                value = node.annotation.slice.value  # type: ignore
+            else:
+                value = node.annotation.slice
+            return f"{value_id}[{node_to_annotation(value)}]"
         else:
             return inspect.Signature.empty
     elif isinstance(node, ast.Subscript):

tests/fixtures/parsing/annotations.py

@@ -0,0 +1,10 @@
+from typing import Any, Dict, List
+
+
+class C:
+    def __init__(self):
+        # https://github.com/pawamoy/pytkdocs/issues/73
+        self.dict_annotation: Dict[str, Any] = {}
+
+        # https://github.com/pawamoy/pytkdocs/issues/75
+        self.list_annotation: List[str] = []

tests/test_parsers/test_annotations.py

@@ -0,0 +1,20 @@
+"""Tests for [the `parsers.attributes` module][pytkdocs.parsers.attributes] on annotations."""
+
+
+from tests.fixtures.parsing import annotations
+
+from pytkdocs.parsers.attributes import get_instance_attributes
+
+
+class TestAnnotations:
+    def setup(self):
+        """Setup reusable attributes."""
+        self.attributes = get_instance_attributes(annotations.C.__init__)
+
+    def test_parse_dict_annotation(self):
+        assert "dict_annotation" in self.attributes
+        assert self.attributes["dict_annotation"]["annotation"] == "Dict[str, Any]"
+
+    def test_parse_list_annotation(self):
+        assert "list_annotation" in self.attributes
+        assert self.attributes["list_annotation"]["annotation"] == "List[str]"