From 2d2cfe79fe91e2540706f4692c8f228d2cf36680 Mon Sep 17 00:00:00 2001
From: Dustin Spicuzza <dustin@virtualroadside.com>
Date: Fri, 17 Jul 2020 03:45:17 -0400
Subject: [PATCH] Use 'raise from' in initialization

---
 include/pybind11/detail/common.h      | 15 +++++++++++++++
 include/pybind11/pytypes.h            |  2 +-
 tests/test_embed/test_interpreter.cpp | 16 ++++++++++++++++
 3 files changed, 32 insertions(+), 1 deletion(-)

diff --git a/include/pybind11/detail/common.h b/include/pybind11/detail/common.h
index 52b0193350..7c5062d607 100644
--- a/include/pybind11/detail/common.h
+++ b/include/pybind11/detail/common.h
@@ -276,6 +276,19 @@ extern "C" {
         }                                                                      \
     }
 
+#if PY_VERSION_HEX >= 0x03030000
+
+#define PYBIND11_CATCH_INIT_EXCEPTIONS \
+        catch (pybind11::error_already_set &e) {                                 \
+            pybind11::raise_from(e, PyExc_ImportError, "initialization failed"); \
+            return nullptr;                                                      \
+        } catch (const std::exception &e) {                                      \
+            PyErr_SetString(PyExc_ImportError, e.what());                        \
+            return nullptr;                                                      \
+        }                                                                        \
+
+#else
+
 #define PYBIND11_CATCH_INIT_EXCEPTIONS \
         catch (pybind11::error_already_set &e) {                               \
             PyErr_SetString(PyExc_ImportError, e.what());                      \
@@ -285,6 +298,8 @@ extern "C" {
             return nullptr;                                                    \
         }                                                                      \
 
+#endif
+
 /** \rst
     ***Deprecated in favor of PYBIND11_MODULE***
 
diff --git a/include/pybind11/pytypes.h b/include/pybind11/pytypes.h
index 0b41695328..360a2e5fce 100644
--- a/include/pybind11/pytypes.h
+++ b/include/pybind11/pytypes.h
@@ -386,7 +386,7 @@ class PYBIND11_EXPORT error_already_set : public std::runtime_error {
 /// 'raise from' to indicate that the chosen error was caused by the original error
 inline void raise_from(PyObject *type, const char *message) {
     // from cpython/errors.c _PyErr_FormatVFromCause
-    PyObject *exc, *val, *val2, *tb;
+    PyObject *exc = nullptr, *val = nullptr, *val2 = nullptr, *tb = nullptr;
     PyErr_Fetch(&exc, &val, &tb);
 
     PyErr_NormalizeException(&exc, &val, &tb);
diff --git a/tests/test_embed/test_interpreter.cpp b/tests/test_embed/test_interpreter.cpp
index 6925ee9782..8e45254332 100644
--- a/tests/test_embed/test_interpreter.cpp
+++ b/tests/test_embed/test_interpreter.cpp
@@ -74,8 +74,24 @@ TEST_CASE("Import error handling") {
     REQUIRE_NOTHROW(py::module_::import("widget_module"));
     REQUIRE_THROWS_WITH(py::module_::import("throw_exception"),
                         "ImportError: C++ Error");
+#if PY_VERSION_HEX >= 0x03030000
+    REQUIRE_THROWS_WITH(py::module_::import("throw_error_already_set"),
+                        Catch::Contains("ImportError: initialization failed"));
+
+    auto locals = py::dict("is_keyerror"_a=false, "message"_a="not set");
+    py::exec(R"(
+        try:
+            import throw_error_already_set
+        except ImportError as e:
+            is_keyerror = type(e.__cause__) == KeyError
+            message = str(e.__cause__)
+    )", py::globals(), locals);
+    REQUIRE(locals["is_keyerror"].cast<bool>() == true);
+    REQUIRE(locals["message"].cast<std::string>() == "'missing'");
+#else
     REQUIRE_THROWS_WITH(py::module_::import("throw_error_already_set"),
                         Catch::Contains("ImportError: KeyError"));
+#endif
 }
 
 TEST_CASE("There can be only one interpreter") {