Add ValueErrorOnNone and RuntimeErrorOnNone to raise errors on nullpt…

…r assignments

PiperOrigin-RevId: 622187569

clif/python/README.md

@@ -269,6 +269,8 @@ The standard CLIF library comes with the following postprocessor functions:
 
 *   `ValueErrorOnFalse` takes first return value as bool, drops it from output
     if True or raise a ValueError if it's False.
+*   `ValueErrorOnNone` raises a ValueError if any of the return values are None,
+    corresponding to `nullptr` assignments.
 *   `chr` is a Python built-in function useful to convert int/uint8 (from C++
     char) to a Python 1-character string.
 

clif/python/postproc.py

@@ -59,3 +59,20 @@ def RuntimeErrorOnFalse(ok, *args):
 def IgnoreTrueOrFalse(ok, *args):
   """Returns None / arg / (args,...) unconditionally, ignoring ok value."""
   return _RaiseOnFalse('IgnoreTrueOrFalse', None, ok, *args)
+
+
+def _RaiseOnNone(error_class, *args):
+  """Raises error_class if args contain None, or returns args[0] / args."""
+  if None in args:
+    raise error_class('CLIF wrapped call returned None')
+  return args if len(args) > 1 else args[0]
+
+
+def ValueErrorOnNone(obj, *args):
+  """Raises ValueError if args contain None, or returns args[0] / args."""
+  return _RaiseOnNone(ValueError, obj, *args)
+
+
+def RuntimeErrorOnNone(obj, *args):
+  """Raises RuntimeError if args contain None, or returns args[0] / args."""
+  return _RaiseOnNone(RuntimeError, obj, *args)

clif/python/postproc_test.py

@@ -44,10 +44,30 @@ def testExceptionType(self, caller_name, error_type):
     if error_type is not None:
       for args in ((False,), (False, 1), (False, 1, 2)):
         with self.assertRaises(error_type) as ctx:
-          postproc_function(False)
-        self.assertEqual(
-            str(ctx.exception),
-            'CLIF wrapped call returned False')
+          postproc_function(*args)
+        self.assertEqual(str(ctx.exception), 'CLIF wrapped call returned False')
+
+  @parameterized.parameterized.expand((
+      (postproc.ValueErrorOnNone, ValueError),
+      (postproc.RuntimeErrorOnNone, RuntimeError),
+  ))
+  def testNoneExceptionType(self, postproc_function, error_type):
+    self.assertEqual(postproc_function(True), True)
+    self.assertEqual(postproc_function(False), False)
+    self.assertEqual(postproc_function(1), 1)
+    self.assertEqual(postproc_function(False, 2), (False, 2))
+    self.assertEqual(postproc_function(1, 2), (1, 2))
+    for args in (
+        (None,),
+        (None, 1),
+        (None, 1, 2),
+        (1, 2, None),
+        (1, None),
+        (None, None),
+    ):
+      with self.assertRaises(error_type) as ctx:
+        postproc_function(*args)
+      self.assertEqual(str(ctx.exception), 'CLIF wrapped call returned None')
 
 
 if __name__ == '__main__':