Improve error-handling in Python Extensions

python_bindings/test/correctness/multi_method_module_test.py

@@ -31,7 +31,21 @@ def test_user_context():
     multi_method_module.user_context(None, ord('q'), output)
     assert output == bytearray("qqqq", "ascii")
 
+def test_aot_call_failure_throws_exception():
+    buffer_input = np.zeros([2, 2], dtype=np.uint8)
+    func_input = np.zeros([2, 2], dtype=np.float32)  # wrong type
+    float_arg = 3.5
+    simple_output = np.zeros([2, 2], dtype=np.float32)
+
+    try:
+        multi_method_module.simple(buffer_input, func_input, float_arg, simple_output)
+    except RuntimeError as e:
+        assert 'Halide Runtime Error: -3 (Input buffer func_input has type uint8 but type of the buffer passed in is float32)' in str(e), str(e)
+    else:
+        assert False, 'Did not see expected exception, saw: ' + str(e)
 
 if __name__ == "__main__":
     test_simple()
     test_user_context()
+    test_aot_call_failure_throws_exception()
+

src/PythonExtensionGen.cpp

@@ -104,6 +104,7 @@ PythonExtensionGen::PythonExtensionGen(std::ostream &dest)
 }
 
 void PythonExtensionGen::compile(const Module &module) {
+    dest << "#include <string>\n";
     dest << "#include <Python.h>\n";
     dest << "#include \"HalideRuntime.h\"\n\n";
 
@@ -269,6 +270,10 @@ namespace Halide::PythonExtensions {
 #undef X
 }  // namespace Halide::PythonExtensions
 
+namespace Halide::PythonRuntime {
+      thread_local std::string current_error;
+}  // namespace Halide::PythonRuntime
+
 namespace {
 
 #define _HALIDE_STRINGIFY(x)            #x
@@ -295,12 +300,36 @@ PyModuleDef _moduledef = {
     nullptr,                                                        // free
 };
 
+void _module_halide_error(void *user_context, const char *msg) {
+    using Halide::PythonRuntime::current_error;
+    if (current_error.empty()) {
+        // fprintf(stderr, "Setting current_error=(%s)\n", msg);
+        current_error = msg;
+    } else {
+        // fprintf(stderr, "Warning: error (%s) ignored because current_error=(%s)\n", msg, current_error.c_str());
+    }
+}
+
+void _module_halide_print(void *user_context, const char *msg) {
+    PySys_FormatStdout("%s", msg);
+}
+
 }  // namespace
 
 extern "C" {
 
+#ifdef HALIDE_PYTHON_EXTENSION_INCLUDE_RUNTIME_SUBMODULE
+extern PyObject *_halide_runtime_submodule_impl(PyObject *module);
+#endif
+
 HALIDE_EXPORT_SYMBOL PyObject *_HALIDE_EXPAND_AND_CONCAT(PyInit_, HALIDE_PYTHON_EXTENSION_MODULE)() {
-    return PyModule_Create(&_moduledef);
+    PyObject *m = PyModule_Create(&_moduledef);
+#ifdef HALIDE_PYTHON_EXTENSION_INCLUDE_RUNTIME_SUBMODULE
+    (void)_halide_runtime_submodule_impl(m);
+#endif
+    halide_set_error_handler(_module_halide_error);
+    halide_set_custom_print(_module_halide_print);
+    return m;
 }
 
 }  // extern "C"
@@ -323,9 +352,12 @@ void PythonExtensionGen::compile(const LoweredFunc &f) {
 
     dest << "#ifndef HALIDE_PYTHON_EXTENSION_OMIT_FUNCTION_DEFINITIONS\n";
     dest << "\n";
+    dest << "namespace Halide::PythonRuntime {\n";
+    dest << "extern thread_local std::string current_error;\n";
+    dest << "}  // namespace Halide::PythonRuntime\n";
+    dest << "\n";
     dest << "namespace Halide::PythonExtensions {\n";
     dest << "\n";
-
     dest << "namespace {\n";
     dest << "\n";
     dest << indent << "const char* const " << basename << "_kwlist[] = {\n";
@@ -369,12 +401,12 @@ void PythonExtensionGen::compile(const LoweredFunc &f) {
         dest << print_type(&arg).first;
     }
     dest << "\", (char**)" << basename << "_kwlist\n";
+    indent.indent += 2;
     for (size_t i = 0; i < args.size(); i++) {
-        indent.indent += 2;
         dest << indent << ", &py_" << arg_names[i] << "\n";
-        indent.indent -= 2;
     }
-    dest << ")) {\n";
+    indent.indent -= 2;
+    dest << indent << ")) {\n";
     indent.indent += 2;
     dest << indent << "PyErr_Format(PyExc_ValueError, \"Internal error\");\n";
     dest << indent << "return nullptr;\n";
@@ -430,7 +462,9 @@ void PythonExtensionGen::compile(const LoweredFunc &f) {
     }
     dest << indent << "if (result != 0) {\n";
     indent.indent += 2;
-    dest << indent << "PyErr_Format(PyExc_ValueError, \"Halide error %d\", result);\n";
+    dest << indent << "std::string take;\n";
+    dest << indent << "std::swap(take, Halide::PythonRuntime::current_error);\n";
+    dest << indent << "PyErr_Format(PyExc_RuntimeError, \"Halide Runtime Error: %d (%s)\", result, take.c_str());\n";
     dest << indent << "return nullptr;\n";
     indent.indent -= 2;
     dest << indent << "}\n";