Handle unsupported pybind inputs non-fatally

Summary: Currently, passing unsupported python types to pybind method execution, such as lists, dicts, or tuples, will crash the kernel due to hitting an assert. This PR updates the logic to raise an exception, which gets nicely bubbled up to the notebook. This gives the user a nicer error message and does not crash the bento/jupyter process.

Differential Revision: D74118509

Author: GregoryComer

extension/pybindings/pybindings.cpp

@@ -757,7 +757,10 @@ struct PyModule final {
       } else if (py::isinstance<py::int_>(python_input)) {
         cpp_inputs.push_back(EValue(py::cast<int64_t>(python_input)));
       } else {
-        ET_ASSERT_UNREACHABLE_MSG("Unsupported pytype: %s", type_str.c_str());
+        throw std::runtime_error(
+          "Unsupported python type " + 
+          type_str + 
+          ". Ensure that inputs are passed as a flat list of tensors.");
       }
     }
 

extension/pybindings/test/make_test.py

@@ -6,7 +6,9 @@
 
 # pyre-unsafe
 
+import sys
 import unittest
+from io import StringIO
 from types import ModuleType
 from typing import Any, Callable, Optional, Tuple
 
@@ -16,6 +18,23 @@
 from torch.export import export
 
 
+class RedirectedStderr:
+    def __init__(self):
+        self._stderr = None
+        self._string_io = None
+
+    def __enter__(self):
+        self._stderr = sys.stderr
+        sys.stderr = self._string_io = StringIO()
+        return self
+
+    def __exit__(self, type, value, traceback):
+        sys.stderr = self._stderr
+
+    def __str__(self):
+        return self._string_io.getvalue()
+
+
 class ModuleAdd(torch.nn.Module):
     """The module to serialize and execute."""
 
@@ -237,25 +256,6 @@ def test_module_single_input(tester):
             tester.assertEqual(str(expected), str(executorch_output))
 
         def test_stderr_redirect(tester):
-            import sys
-            from io import StringIO
-
-            class RedirectedStderr:
-                def __init__(self):
-                    self._stderr = None
-                    self._string_io = None
-
-                def __enter__(self):
-                    self._stderr = sys.stderr
-                    sys.stderr = self._string_io = StringIO()
-                    return self
-
-                def __exit__(self, type, value, traceback):
-                    sys.stderr = self._stderr
-
-                def __str__(self):
-                    return self._string_io.getvalue()
-
             with RedirectedStderr() as out:
                 try:
                     # Create an ExecuTorch program from ModuleAdd.
@@ -464,6 +464,16 @@ def test_verification_config(tester) -> None:
 
                 tester.assertEqual(str(expected), str(executorch_output))
 
+        def test_unsupported_input_type(tester):
+            exported_program, inputs = create_program(ModuleAdd())
+            executorch_module = load_fn(exported_program.buffer)
+
+            # Pass an unsupported input type to the module.
+            inputs = ([*inputs],)
+
+            # This should raise a Python error, not hit a fatal assert in the C++ code.
+            tester.assertRaises(RuntimeError, executorch_module, inputs)
+
         ######### RUN TEST CASES #########
         test_e2e(tester)
         test_multiple_entry(tester)
@@ -479,5 +489,6 @@ def test_verification_config(tester) -> None:
         test_method_meta(tester)
         test_bad_name(tester)
         test_verification_config(tester)
+        test_unsupported_input_type(tester)
 
     return wrapper