From cfc848a137bd99a172329091c01fe29aeb552098 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Mon, 11 Jan 2021 22:06:18 -0800
Subject: [PATCH] Retrieving smart_holder pointer in
 type_caster<std::unique_ptr<mpty[ const]>>::load, and using it cast_op
 operators.

---
 tests/test_classh_wip.cpp | 22 ++++++----------------
 tests/test_classh_wip.py  | 19 +++++++++++++++++--
 2 files changed, 23 insertions(+), 18 deletions(-)

diff --git a/tests/test_classh_wip.cpp b/tests/test_classh_wip.cpp
index 3de45a438..1767af9d3 100644
--- a/tests/test_classh_wip.cpp
+++ b/tests/test_classh_wip.cpp
@@ -33,8 +33,8 @@ std::string pass_mpty_shcp(std::shared_ptr<mpty const> obj) { return "pass_shcp:
 std::unique_ptr<mpty>       rtrn_mpty_uqmp() { return std::unique_ptr<mpty>(new mpty); }
 std::unique_ptr<mpty const> rtrn_mpty_uqcp() { return std::unique_ptr<mpty const>(new mpty); }
 
-const char* pass_mpty_uqmp(std::unique_ptr<mpty>)       { return "load_uqmp"; }
-const char* pass_mpty_uqcp(std::unique_ptr<mpty const>) { return "load_uqcp"; }
+std::string pass_mpty_uqmp(std::unique_ptr<mpty> obj)       { return "pass_uqmp:" + obj->mtxt; }
+std::string pass_mpty_uqcp(std::unique_ptr<mpty const> obj) { return "pass_uqcp:" + obj->mtxt; }
 
 }  // namespace classh_wip
 }  // namespace pybind11_tests
@@ -147,7 +147,7 @@ struct type_caster<std::shared_ptr<mpty const>> : smart_holder_type_caster_load<
 };
 
 template <>
-struct type_caster<std::unique_ptr<mpty>> {
+struct type_caster<std::unique_ptr<mpty>> : smart_holder_type_caster_load<mpty> {
     static constexpr auto name = _<std::unique_ptr<mpty>>();
 
     static handle cast(std::unique_ptr<mpty>&& /*src*/,
@@ -158,16 +158,11 @@ struct type_caster<std::unique_ptr<mpty>> {
 
     template <typename> using cast_op_type = std::unique_ptr<mpty>;
 
-    operator std::unique_ptr<mpty>() { return rtrn_mpty_uqmp(); }
-
-    bool load(handle src, bool /*convert*/) {
-        if (!isinstance<mpty>(src)) return false;
-        return true;
-    }
+    operator std::unique_ptr<mpty>() { return smhldr_ptr->as_unique_ptr<mpty>(); }
 };
 
 template <>
-struct type_caster<std::unique_ptr<mpty const>> {
+struct type_caster<std::unique_ptr<mpty const>> : smart_holder_type_caster_load<mpty> {
     static constexpr auto name = _<std::unique_ptr<mpty const>>();
 
     static handle cast(std::unique_ptr<mpty const>&& /*src*/,
@@ -178,12 +173,7 @@ struct type_caster<std::unique_ptr<mpty const>> {
 
     template <typename> using cast_op_type = std::unique_ptr<mpty const>;
 
-    operator std::unique_ptr<mpty const>() { return rtrn_mpty_uqcp(); }
-
-    bool load(handle src, bool /*convert*/) {
-        if (!isinstance<mpty>(src)) return false;
-        return true;
-    }
+    operator std::unique_ptr<mpty const>() { return smhldr_ptr->as_unique_ptr<mpty>(); }
 };
 
 }  // namespace detail
diff --git a/tests/test_classh_wip.py b/tests/test_classh_wip.py
index 7d6d0bb0f..4ecdee8b6 100644
--- a/tests/test_classh_wip.py
+++ b/tests/test_classh_wip.py
@@ -47,5 +47,20 @@ def test_cast_unique_ptr():
 
 
 def test_load_unique_ptr():
-    assert m.pass_mpty_uqmp(m.mpty()) == "load_uqmp"
-    assert m.pass_mpty_uqcp(m.mpty()) == "load_uqcp"
+    assert m.pass_mpty_uqmp(m.mpty("Uqmp")) == "pass_uqmp:Uqmp"
+    assert m.pass_mpty_uqcp(m.mpty("Uqcp")) == "pass_uqcp:Uqcp"
+
+
+@pytest.mark.parametrize(
+    "pass_mpty, argm, rtrn",
+    [
+        (m.pass_mpty_uqmp, "Uqmp", "pass_uqmp:Uqmp"),
+        (m.pass_mpty_uqcp, "Uqcp", "pass_uqcp:Uqcp"),
+    ],
+)
+def test_pass_unique_ptr_disowns(pass_mpty, argm, rtrn):
+    obj = m.mpty(argm)
+    assert pass_mpty(obj) == rtrn
+    with pytest.raises(RuntimeError) as exc_info:
+        m.pass_mpty_uqmp(obj)
+    assert str(exc_info.value) == "Cannot disown nullptr (as_unique_ptr)."