fix: wrap None in code when used as annotation

quartodoc/renderers/md_renderer.py

@@ -315,12 +315,26 @@ def render_annotation(self, el: str) -> str:
         Parameters
         ----------
         el:
-            An object representing a type annotation.
+            An object representing a type annotation. Can be a structural string
+            (like '[', ']', ' | '), literal contents, or "None" when None is used
+            as in "x: int | None".
         """
+        # Special case for None - it's used as shorthand for NoneType in type annotations
+        # e.g., "int | None" is common for Optional types
+        if el == "None":
+            if self.render_interlinks:
+                # Render as markdown link like other types
+                return f"[None](`None`)"
+            else:
+                # Render without backticks like any instance (e.g. 1, "a")
+                return "None"
+
+        # For structural strings (brackets, operators, etc.), use existing logic
         return sanitize(el, escape_quotes=True)
 
     @dispatch
     def render_annotation(self, el: None) -> str:
+        # this is used to indicate no annotation, not the literal None
         return ""
 
     @dispatch

quartodoc/tests/__snapshots__/test_renderers.ambr

@@ -13,15 +13,15 @@
 
   ## Parameters {.doc-section .doc-section-parameters}
 
-  +--------+--------------------------------------------------------------------------------------+-------------------------------+------------+
-  | Name   | Type                                                                                 | Description                   | Default    |
-  +========+======================================================================================+===============================+============+
-  | x      | [list](`list`)\[[C](`quartodoc.tests.example_signature.C`) \| [int](`int`) \| None\] | The x parameter               | _required_ |
-  +--------+--------------------------------------------------------------------------------------+-------------------------------+------------+
-  | y      | [pathlib](`pathlib`).[Pathlib](`pathlib.Pathlib`)                                    | The y parameter               | _required_ |
-  +--------+--------------------------------------------------------------------------------------+-------------------------------+------------+
-  | z      |                                                                                      | The z parameter (unannotated) | _required_ |
-  +--------+--------------------------------------------------------------------------------------+-------------------------------+------------+
+  +--------+------------------------------------------------------------------------------------------------+-------------------------------+------------+
+  | Name   | Type                                                                                           | Description                   | Default    |
+  +========+================================================================================================+===============================+============+
+  | x      | [list](`list`)\[[C](`quartodoc.tests.example_signature.C`) \| [int](`int`) \| [None](`None`)\] | The x parameter               | _required_ |
+  +--------+------------------------------------------------------------------------------------------------+-------------------------------+------------+
+  | y      | [pathlib](`pathlib`).[Pathlib](`pathlib.Pathlib`)                                              | The y parameter               | _required_ |
+  +--------+------------------------------------------------------------------------------------------------+-------------------------------+------------+
+  | z      |                                                                                                | The z parameter (unannotated) | _required_ |
+  +--------+------------------------------------------------------------------------------------------------+-------------------------------+------------+
   '''
 # ---
 # name: test_render_annotations_complex_no_interlinks

quartodoc/tests/test_renderers.py

@@ -213,6 +213,27 @@ def test_render_annotations_complex_no_interlinks(snapshot):
     assert res == snapshot
 
 
+def test_render_annotation_none():
+    """Test rendering of None in type annotations.
+
+    None is special in type annotations - it's used as shorthand for NoneType
+    in annotations like 'int | None'. It should be rendered consistently with
+    other types like int and str.
+    """
+    renderer_with_links = MdRenderer(render_interlinks=True)
+    renderer_no_links = MdRenderer(render_interlinks=False)
+
+    # Test None with interlinks: should be markdown link
+    with_links = renderer_with_links.render_annotation("None")
+    assert (
+        with_links == "[None](`None`)"
+    ), "None with interlinks should be markdown link"
+
+    # Test None without interlinks: should have backticks
+    without_links = renderer_no_links.render_annotation("None")
+    assert without_links == "None", "None without interlinks should have no backticks"
+
+
 @pytest.mark.parametrize("children", ["embedded", "flat"])
 def test_render_doc_class(snapshot, renderer, children):
     bp = blueprint(Auto(name="quartodoc.tests.example_class.C", children=children))