Fix #8693: autodoc: Default values for overloads are rendered as string

The default values for overloaded functions are rendered as string
literal unexpectedly because autodoc extracts code snippets from
the source code, not actual value (ex. int, ellipsis, and so on).

This introduces a simple wrapper class; `DefaultValue` to render these
code snippets like actual values, not string literals.

CHANGES

@@ -45,6 +45,7 @@ Bugs fixed
 * #8315: autodoc: Failed to resolve struct.Struct type annotation
 * #8652: autodoc: All variable comments in the module are ignored if the module
   contains invalid type comments
+* #8693: autodoc: Default values for overloaded functions are rendered as string
 * #8306: autosummary: mocked modules are documented as empty page when using
   :recursive: option
 * #8618: html: kbd role produces incorrect HTML when compound-key separators (-,

sphinx/util/inspect.py

@@ -499,6 +499,19 @@ def is_builtin_class_method(obj: Any, attr_name: str) -> bool:
     return getattr(builtins, name, None) is cls
 
 
+class DefaultValue:
+    """A simple wrapper for default value of the parameters of overload functions."""
+
+    def __init__(self, value: str) -> None:
+        self.value = value
+
+    def __eq__(self, other: object) -> bool:
+        return self.value == other
+
+    def __repr__(self) -> str:
+        return self.value
+
+
 def _should_unwrap(subject: Callable) -> bool:
     """Check the function should be unwrapped on getting signature."""
     if (safe_getattr(subject, '__globals__', None) and
@@ -704,7 +717,7 @@ def signature_from_ast(node: ast.FunctionDef, code: str = '') -> inspect.Signatu
             if defaults[i] is Parameter.empty:
                 default = Parameter.empty
             else:
-                default = ast_unparse(defaults[i], code)
+                default = DefaultValue(ast_unparse(defaults[i], code))
 
             annotation = ast_unparse(arg.annotation, code) or Parameter.empty
             params.append(Parameter(arg.arg, Parameter.POSITIONAL_ONLY,
@@ -714,7 +727,7 @@ def signature_from_ast(node: ast.FunctionDef, code: str = '') -> inspect.Signatu
         if defaults[i + posonlyargs] is Parameter.empty:
             default = Parameter.empty
         else:
-            default = ast_unparse(defaults[i + posonlyargs], code)
+            default = DefaultValue(ast_unparse(defaults[i + posonlyargs], code))
 
         annotation = ast_unparse(arg.annotation, code) or Parameter.empty
         params.append(Parameter(arg.arg, Parameter.POSITIONAL_OR_KEYWORD,

tests/roots/test-ext-autodoc/target/overload.py

@@ -2,17 +2,17 @@ from typing import Any, overload
 
 
 @overload
-def sum(x: int, y: int) -> int:
+def sum(x: int, y: int = 0) -> int:
     ...
 
 
 @overload
-def sum(x: "float", y: "float") -> "float":
+def sum(x: "float", y: "float" = 0.0) -> "float":
     ...
 
 
 @overload
-def sum(x: str, y: str) -> str:
+def sum(x: str, y: str = ...) -> str:
     ...
 
 
@@ -25,15 +25,15 @@ class Math:
     """docstring"""
 
     @overload
-    def sum(self, x: int, y: int) -> int:
+    def sum(self, x: int, y: int = 0) -> int:
         ...
 
     @overload
-    def sum(self, x: "float", y: "float") -> "float":
+    def sum(self, x: "float", y: "float" = 0.0) -> "float":
         ...
 
     @overload
-    def sum(self, x: str, y: str) -> str:
+    def sum(self, x: str, y: str = ...) -> str:
         ...
 
     def sum(self, x, y):

tests/test_ext_autodoc.py

@@ -2078,17 +2078,17 @@ def test_overload(app):
         '   docstring',
         '',
         '',
-        '   .. py:method:: Math.sum(x: int, y: int) -> int',
-        '                  Math.sum(x: float, y: float) -> float',
-        '                  Math.sum(x: str, y: str) -> str',
+        '   .. py:method:: Math.sum(x: int, y: int = 0) -> int',
+        '                  Math.sum(x: float, y: float = 0.0) -> float',
+        '                  Math.sum(x: str, y: str = ...) -> str',
         '      :module: target.overload',
         '',
         '      docstring',
         '',
         '',
-        '.. py:function:: sum(x: int, y: int) -> int',
-        '                 sum(x: float, y: float) -> float',
-        '                 sum(x: str, y: str) -> str',
+        '.. py:function:: sum(x: int, y: int = 0) -> int',
+        '                 sum(x: float, y: float = 0.0) -> float',
+        '                 sum(x: str, y: str = ...) -> str',
         '   :module: target.overload',
         '',
         '   docstring',