Add test for mixing STL casters and local binders across modules

One module uses a generic vector caster from `<pybind11/stl.h>` while
the other exports `std::vector<int>` with a local `py:bind_vector`.

tests/local_bindings.h

@@ -21,6 +21,14 @@ using MixedLocalGlobal = LocalBase<4>;
 /// Mixed: global first, then local (which fails)
 using MixedGlobalLocal = LocalBase<5>;
 
+using LocalVec = std::vector<LocalType>;
+using LocalVec2 = std::vector<NonLocal2>;
+using LocalMap = std::unordered_map<std::string, LocalType>;
+using NonLocalVec = std::vector<NonLocalType>;
+using NonLocalVec2 = std::vector<NonLocal2>;
+using NonLocalMap = std::unordered_map<std::string, NonLocalType>;
+using NonLocalMap2 = std::unordered_map<std::string, uint8_t>;
+
 // Simple bindings (used with the above):
 template <typename T, int Adjust, typename... Args>
 py::class_<T> bind_local(Args && ...args) {

tests/pybind11_cross_module_tests.cpp

@@ -10,6 +10,7 @@
 #include "pybind11_tests.h"
 #include "local_bindings.h"
 #include <pybind11/stl_bind.h>
+#include <numeric>
 
 PYBIND11_MODULE(pybind11_cross_module_tests, m) {
     m.doc() = "pybind11 cross-module test module";
@@ -44,25 +45,25 @@ PYBIND11_MODULE(pybind11_cross_module_tests, m) {
 
     // test_stl_bind_local
     // stl_bind.h binders defaults to py::module_local if the types are local or converting:
-    py::bind_vector<std::vector<LocalType>>(m, "LocalVec");
-    py::bind_map<std::unordered_map<std::string, LocalType>>(m, "LocalMap");
+    py::bind_vector<LocalVec>(m, "LocalVec");
+    py::bind_map<LocalMap>(m, "LocalMap");
+
+    // test_stl_bind_global
     // and global if the type (or one of the types, for the map) is global (so these will fail,
     // assuming pybind11_tests is already loaded):
     m.def("register_nonlocal_vec", [m]() {
-        py::bind_vector<std::vector<NonLocalType>>(m, "NonLocalVec");
+        py::bind_vector<NonLocalVec>(m, "NonLocalVec");
     });
     m.def("register_nonlocal_map", [m]() {
-        py::bind_map<std::unordered_map<std::string, NonLocalType>>(m, "NonLocalMap");
+        py::bind_map<NonLocalMap>(m, "NonLocalMap");
     });
-
-    // test_stl_bind_global
     // The default can, however, be overridden to global using `py::module_local()` or
     // `py::module_local(false)`.
     // Explicitly made local:
-    py::bind_vector<std::vector<NonLocal2>>(m, "NonLocalVec2", py::module_local());
+    py::bind_vector<NonLocalVec2>(m, "NonLocalVec2", py::module_local());
     // Explicitly made global (and so will fail to bind):
     m.def("register_nonlocal_map2", [m]() {
-        py::bind_map<std::unordered_map<std::string, uint8_t>>(m, "NonLocalMap2", py::module_local(false));
+        py::bind_map<NonLocalMap2>(m, "NonLocalMap2", py::module_local(false));
     });
 
     // test_mixed_local_global
@@ -79,4 +80,11 @@ PYBIND11_MODULE(pybind11_cross_module_tests, m) {
 
     // test_internal_locals_differ
     m.def("local_cpp_types_addr", []() { return (uintptr_t) &py::detail::registered_local_types_cpp(); });
+
+    // test_stl_caster_vs_stl_bind
+    py::bind_vector<std::vector<int>>(m, "VectorInt");
+
+    m.def("load_vector_via_binding", [](std::vector<int> &v) {
+        return std::accumulate(v.begin(), v.end(), 0);
+    });
 }

tests/test_local_bindings.cpp

@@ -10,10 +10,18 @@
 
 #include "pybind11_tests.h"
 #include "local_bindings.h"
+#include <pybind11/stl.h>
 #include <pybind11/stl_bind.h>
+#include <numeric>
+
+PYBIND11_MAKE_OPAQUE(LocalVec);
+PYBIND11_MAKE_OPAQUE(LocalVec2);
+PYBIND11_MAKE_OPAQUE(LocalMap);
+PYBIND11_MAKE_OPAQUE(NonLocalVec);
+PYBIND11_MAKE_OPAQUE(NonLocalMap);
+PYBIND11_MAKE_OPAQUE(NonLocalMap2);
 
 TEST_SUBMODULE(local_bindings, m) {
-
     // test_local_bindings
     // Register a class with py::module_local:
     bind_local<LocalType, -1>(m, "LocalType", py::module_local())
@@ -45,17 +53,17 @@ TEST_SUBMODULE(local_bindings, m) {
 
     // test_stl_bind_local
     // stl_bind.h binders defaults to py::module_local if the types are local or converting:
-    py::bind_vector<std::vector<LocalType>>(m, "LocalVec");
-    py::bind_map<std::unordered_map<std::string, LocalType>>(m, "LocalMap");
+    py::bind_vector<LocalVec>(m, "LocalVec");
+    py::bind_map<LocalMap>(m, "LocalMap");
     // and global if the type (or one of the types, for the map) is global:
-    py::bind_vector<std::vector<NonLocalType>>(m, "NonLocalVec");
-    py::bind_map<std::unordered_map<std::string, NonLocalType>>(m, "NonLocalMap");
+    py::bind_vector<NonLocalVec>(m, "NonLocalVec");
+    py::bind_map<NonLocalMap>(m, "NonLocalMap");
 
     // test_stl_bind_global
     // They can, however, be overridden to global using `py::module_local(false)`:
     bind_local<NonLocal2, 10>(m, "NonLocal2");
-    py::bind_vector<std::vector<NonLocal2>>(m, "LocalVec2", py::module_local());
-    py::bind_map<std::unordered_map<std::string, uint8_t>>(m, "NonLocalMap2", py::module_local(false));
+    py::bind_vector<LocalVec2>(m, "LocalVec2", py::module_local());
+    py::bind_map<NonLocalMap2>(m, "NonLocalMap2", py::module_local(false));
 
     // test_mixed_local_global
     // We try this both with the global type registered first and vice versa (the order shouldn't
@@ -71,4 +79,9 @@ TEST_SUBMODULE(local_bindings, m) {
 
     // test_internal_locals_differ
     m.def("local_cpp_types_addr", []() { return (uintptr_t) &py::detail::registered_local_types_cpp(); });
+
+    // test_stl_caster_vs_stl_bind
+    m.def("load_vector_via_caster", [](std::vector<int> v) {
+        return std::accumulate(v.begin(), v.end(), 0);
+    });
 }

tests/test_local_bindings.py

@@ -4,13 +4,12 @@ from pybind11_tests import local_bindings as m
 
 
 def test_local_bindings():
-    """Tests that duplicate py::local class bindings work across modules"""
+    """Tests that duplicate `py::module_local` class bindings work across modules"""
 
     # Make sure we can load the second module with the conflicting (but local) definition:
     import pybind11_cross_module_tests as cm
 
     i1 = m.LocalType(5)
-
     assert i1.get() == 4
     assert i1.get3() == 8
 
@@ -138,3 +137,24 @@ def test_internal_locals_differ():
     """Makes sure the internal local type map differs across the two modules"""
     import pybind11_cross_module_tests as cm
     assert m.local_cpp_types_addr() != cm.local_cpp_types_addr()
+
+
+def test_stl_caster_vs_stl_bind(msg):
+    """One module uses a generic vector caster from `<pybind11/stl.h>` while the other
+    exports `std::vector<int>` via `py:bind_vector` and `py::module_local`"""
+    import pybind11_cross_module_tests as cm
+
+    v1 = cm.VectorInt([1, 2, 3])
+    assert m.load_vector_via_caster(v1) == 6
+    assert cm.load_vector_via_binding(v1) == 6
+
+    v2 = [1, 2, 3]
+    assert m.load_vector_via_caster(v2) == 6
+    with pytest.raises(TypeError) as excinfo:
+        cm.load_vector_via_binding(v2) == 6
+    assert msg(excinfo.value) == """
+    load_vector_via_binding(): incompatible function arguments. The following argument types are supported:
+        1. (arg0: pybind11_cross_module_tests.VectorInt) -> int
+
+    Invoked with: [1, 2, 3]
+    """  # noqa: E501 line too long