gh-85267: Improvements to inspect.signature __text_signature__ handling

Lib/inspect.py

@@ -2100,7 +2100,7 @@ def _signature_strip_non_python_syntax(signature):
  self_parameter = None
  last_positional_only = None
 
- lines = [l.encode('ascii') for l in signature.split('\n')]
+ lines = [l.encode('ascii') for l in signature.split('\n') if l]
  generator = iter(lines).__next__
  token_stream = tokenize.tokenize(generator)
 
@@ -2199,11 +2199,11 @@ def wrap_value(s):
  try:
  value = eval(s, sys_module_dict)
  except NameError:
- raise RuntimeError()
+ raise ValueError
 
  if isinstance(value, (str, int, float, bytes, bool, type(None))):
  return ast.Constant(value)
- raise RuntimeError()
+ raise ValueError
 
  class RewriteSymbolics(ast.NodeTransformer):
  def visit_Attribute(self, node):
@@ -2213,7 +2213,7 @@ def visit_Attribute(self, node):
  a.append(n.attr)
  n = n.value
  if not isinstance(n, ast.Name):
- raise RuntimeError()
+ raise ValueError
  a.append(n.id)
  value = ".".join(reversed(a))
  return wrap_value(value)
@@ -2223,14 +2223,29 @@ def visit_Name(self, node):
  raise ValueError()
  return wrap_value(node.id)
 
+ def visit_BinOp(self, node):
+ # Support constant folding of a couple simple binary operations
+ # commonly used to define default values in text signatures
+ left = self.visit(node.left)
+ right = self.visit(node.right)
+ if not isinstance(left, ast.Constant) or not isinstance(right, ast.Constant):
+ raise ValueError
+ if isinstance(node.op, ast.Add):
+ return ast.Constant(left.value + right.value)
+ elif isinstance(node.op, ast.Sub):
+ return ast.Constant(left.value - right.value)
+ elif isinstance(node.op, ast.BitOr):
+ return ast.Constant(left.value | right.value)
+ raise ValueError
+
  def p(name_node, default_node, default=empty):
  name = parse_name(name_node)
  if default_node and default_node is not _empty:
  try:
  default_node = RewriteSymbolics().visit(default_node)
  default = ast.literal_eval(default_node)
  except ValueError:
-return None
+raise ValueError("{!r} builtin has invalid signature".format(obj)) from None
  parameters.append(Parameter(name, kind, default=default, annotation=empty))
 
  # non-keyword-only parameters

Lib/test/test_inspect.py

@@ -2480,7 +2480,7 @@ def p(name): return signature.parameters[name].default
  self.assertEqual(p('f'), False)
  self.assertEqual(p('local'), 3)
  self.assertEqual(p('sys'), sys.maxsize)
- self.assertNotIn('exp', signature.parameters)
+ self.assertEqual(p('exp'), sys.maxsize - 1)
 
  test_callable(object)
 
@@ -4246,10 +4246,29 @@ def func(*args, **kwargs):
  sig = inspect.signature(func)
  self.assertIsNotNone(sig)
  self.assertEqual(str(sig), '(self, /, a, b=1, *args, c, d=2, **kwargs)')
+
  func.__text_signature__ = '($self, a, b=1, /, *args, c, d=2, **kwargs)'
  sig = inspect.signature(func)
  self.assertEqual(str(sig), '(self, a, b=1, /, *args, c, d=2, **kwargs)')
 
+ func.__text_signature__ = '(self, a=1+2, b=4-3, c=1 | 3 | 16)'
+ sig = inspect.signature(func)
+ self.assertEqual(str(sig), '(self, a=3, b=1, c=19)')
+
+ func.__text_signature__ = '(self, a=1,\nb=2,\n\n\n c=3)'
+ sig = inspect.signature(func)
+ self.assertEqual(str(sig), '(self, a=1, b=2, c=3)')
+
+ func.__text_signature__ = '(self, x=does_not_exist)'
+ with self.assertRaises(ValueError):
+ inspect.signature(func)
+ func.__text_signature__ = '(self, x=sys, y=inspect)'
+ with self.assertRaises(ValueError):
+ inspect.signature(func)
+ func.__text_signature__ = '(self, 123)'
+ with self.assertRaises(ValueError):
+ inspect.signature(func)
+
  def test_base_class_have_text_signature(self):
  # see issue 43118
  from test.ann_module7 import BufferedReader

Misc/NEWS.d/next/Library/2022-10-28-07-24-34.gh-issue-85267.xUy_Wm.rst

@@ -0,0 +1,6 @@
+Several improvements to :func:`inspect.signature`'s handling of ``__text_signature``.
+- Fixes a case where :func:`inspect.signature` dropped parameters
+- Fixes a case where :func:`inspect.signature` raised :exc:`tokenize.TokenError`
+- Allows :func:`inspect.signature` to understand defaults involving binary operations of constants
+- :func:`inspect.signature` is documented as only raising :exc:`TypeError` or :exc:`ValueError`, but sometimes raised :exc:`RuntimeError`. These cases now raise :exc:`ValueError`
+- Removed a dead code path