pythongh-81677: basic support for annotations in signature strings

Lib/inspect.py

@@ -2208,10 +2208,22 @@ def _signature_fromstr(cls, obj, s, skip_bound_arg=True):
 
     def parse_name(node):
         assert isinstance(node, ast.arg)
-        if node.annotation is not None:
-            raise ValueError("Annotations are not currently supported")
         return node.arg
 
+    def parse_annotation(node):
+        assert isinstance(node, (ast.arg, ast.FunctionDef))
+        if isinstance(node, ast.arg):
+            annotation = node.annotation
+        else:
+            annotation = node.returns
+        if annotation:
+            expr = ast.unparse(annotation)
+            try:
+                return eval(expr, sys_module_dict)
+            except NameError:
+                raise ValueError
+        return empty
+
     def wrap_value(s):
         try:
             value = eval(s, module_dict)
@@ -2266,7 +2278,11 @@ def p(name_node, default_node, default=empty):
                 default = ast.literal_eval(default_node)
             except ValueError:
                 raise ValueError("{!r} builtin has invalid signature".format(obj)) from None
-        parameters.append(Parameter(name, kind, default=default, annotation=empty))
+        try:
+            annotation = parse_annotation(name_node)
+        except ValueError:
+            raise ValueError("{!r} builtin has invalid signature".format(obj)) from None
+        parameters.append(Parameter(name, kind, default=default, annotation=annotation))
 
     # non-keyword-only parameters
     args = reversed(f.args.args)
@@ -2313,7 +2329,12 @@ def p(name_node, default_node, default=empty):
             p = parameters[0].replace(kind=Parameter.POSITIONAL_ONLY)
             parameters[0] = p
 
-    return cls(parameters, return_annotation=cls.empty)
+    try:
+        return_annotation = parse_annotation(f)
+    except ValueError:
+        raise ValueError("{!r} builtin has invalid signature".format(obj)) from None
+
+    return cls(parameters, return_annotation=return_annotation)
 
 
 def _signature_from_builtin(cls, func, skip_bound_arg=True):

Lib/test/test_inspect.py

@@ -4384,6 +4384,33 @@ class MyBufferedReader(BufferedReader):
         sig = inspect.signature(MyBufferedReader)
         self.assertEqual(str(sig), '(raw, buffer_size=8192)')
 
+    def test_annotations_in_text_signature(self):
+        def func(*args, **kwargs):
+            pass
+
+        func.__text_signature__ = '($self, a: int) -> list'
+        sig = inspect.signature(func)
+        self.assertIsNotNone(sig)
+        self.assertEqual(str(sig), '(self, /, a: int) -> list')
+
+        func.__text_signature__ = '($self, a: int | float)'
+        sig = inspect.signature(func)
+        self.assertIsNotNone(sig)
+        self.assertEqual(str(sig), '(self, /, a: int | float)')
+
+        func.__text_signature__ = '($self, a: tuple[int, ...])'
+        sig = inspect.signature(func)
+        self.assertIsNotNone(sig)
+        self.assertEqual(str(sig), '(self, /, a: tuple[int, ...])')
+
+        func.__text_signature__ = '(self, x: spam)'
+        with self.assertRaises(ValueError):
+            inspect.signature(func)
+
+        func.__text_signature__ = '(self, x) -> spam'
+        with self.assertRaises(ValueError):
+            inspect.signature(func)
+
 
 class NTimesUnwrappable:
     def __init__(self, n):