Support callables in Annotated

Author: AA-Turner

sphinx/domains/python/_annotations.py

@@ -161,7 +161,28 @@ def unparse(node: ast.AST) -> list[Node]:
                           addnodes.desc_sig_punctuation('', ')')]
 
             return result
-        raise SyntaxError  # unsupported syntax
+        if isinstance(node, ast.Call):
+            # Call nodes can be used in Annotated type metadata,
+            # for example Annotated[str, ArbitraryTypeValidator(str, len=10)]
+            args = []
+            for arg in node.args:
+                args += unparse(arg)
+                args.append(addnodes.desc_sig_punctuation('', ','))
+                args.append(addnodes.desc_sig_space())
+            for kwd in node.keywords:
+                args.append(addnodes.desc_sig_name(kwd.arg, kwd.arg))  # type: ignore[arg-type]
+                args.append(addnodes.desc_sig_operator('', '='))
+                args += unparse(kwd.value)
+                args.append(addnodes.desc_sig_punctuation('', ','))
+                args.append(addnodes.desc_sig_space())
+            result = [
+                *unparse(node.func),
+                addnodes.desc_sig_punctuation('', '('),
+                *args[:-2],  # skip the final comma and space
+                addnodes.desc_sig_punctuation('', ')'),
+            ]
+            return result
+        raise SyntaxError(f'unsupported syntax: {node}')  # unsupported syntax
 
     def _unparse_pep_604_annotation(node: ast.Subscript) -> list[Node]:
         subscript = node.slice

tests/test_domains/test_domain_py.py

@@ -370,6 +370,27 @@ def test_parse_annotation(app):
                           [desc_sig_punctuation, "]"]))
     assert_node(doctree[0], pending_xref, refdomain="py", reftype="obj", reftarget="typing.Literal")
 
+    # Annotated type with callable gets parsed
+    doctree = _parse_annotation("Annotated[Optional[str], annotated_types.MaxLen(max_length=10)]", app.env)
+    assert_node(doctree, (
+        [pending_xref, 'Annotated'],
+        [desc_sig_punctuation, '['],
+        [pending_xref, 'str'],
+        [desc_sig_space, ' '],
+        [desc_sig_punctuation, '|'],
+        [desc_sig_space, ' '],
+        [pending_xref, 'None'],
+        [desc_sig_punctuation, ','],
+        [desc_sig_space, ' '],
+        [pending_xref, 'annotated_types.MaxLen'],
+        [desc_sig_punctuation, '('],
+        [desc_sig_name, 'max_length'],
+        [desc_sig_operator, '='],
+        [desc_sig_literal_number, '10'],
+        [desc_sig_punctuation, ')'],
+        [desc_sig_punctuation, ']'],
+    ))
+
 
 def test_parse_annotation_suppress(app):
     doctree = _parse_annotation("~typing.Dict[str, str]", app.env)