Add unit tests

Author: oremanj

docs/api_core.rst

@@ -3239,10 +3239,11 @@ additional information and caveats about this feature.
 
 .. cpp:function:: void export_for_interop(handle type)
 
-   Make the Python type object *type*, which was bound in this nanobind domain,
-   be available for import by other binding libraries and other nanobind
-   domains. If they do so, then their bound functions will be able to accept
-   and return instances of *type*.
+   Make the Python type object *type*, which was created by a
+   :cpp:class:`nb::class_` or :cpp:class:`nb::enum_` binding statement in this
+   nanobind domain be available for import by other binding libraries and other
+   nanobind domains. If they do so, then their bound functions will be able to
+   accept and return instances of *type*.
 
    Repeatedly exporting the same type is idempotent.
 

include/nanobind/nb_class.h

@@ -204,7 +204,10 @@ enum class enum_flags : uint32_t {
     is_signed                = (1 << 2),
 
     /// Is the underlying enumeration type Flag?
-    is_flag                = (1 << 3)
+    is_flag                  = (1 << 3),
+
+    /// Was the enum successfully registered with nanobind?
+    is_registered            = (1 << 4),
 };
 
 struct enum_init_data {
@@ -340,6 +343,12 @@ inline void interoperate_by_default(bool export_all = true,
 }
 template <class T = void>
 inline void import_for_interop(handle type) {
+    if constexpr (!std::is_void_v<T>) {
+        static_assert(
+            detail::is_base_caster_v<detail::make_caster<T>>,
+            "Types that are intercepted by a type caster cannot use the "
+            "interoperability feature");
+    }
     detail::nb_type_import(type.ptr(),
                            std::is_void_v<T> ? nullptr : &typeid(T));
 }

src/nb_enum.cpp

@@ -64,6 +64,7 @@ PyObject *enum_create(enum_init_data *ed) noexcept {
     t->type = ed->type;
     t->type_py = (PyTypeObject *) result.ptr();
     t->flags = ed->flags;
+    t->size = ed->size;
     t->enum_tbl.fwd = new enum_map();
     t->enum_tbl.rev = new enum_map();
     t->scope = ed->scope;
@@ -72,7 +73,8 @@ PyObject *enum_create(enum_init_data *ed) noexcept {
         type_init_data *t = (type_init_data *) p;
         delete (enum_map *) t->enum_tbl.fwd;
         delete (enum_map *) t->enum_tbl.rev;
-        nb_type_unregister(t);
+        if (t->flags & (uint32_t) enum_flags::is_registered)
+            nb_type_unregister(t);
         free((char*) t->name);
         delete t;
     });
@@ -86,14 +88,15 @@ PyObject *enum_create(enum_init_data *ed) noexcept {
         return tp;
     }
 
+    t->flags |= (uint32_t) enum_flags::is_registered;
     result.attr("__nb_enum__") = tie_lifetimes;
 
     make_immortal(result.ptr());
 
     return result.release().ptr();
 }
 
-static type_init_data *enum_get_type_data(handle tp) {
+type_init_data *enum_get_type_data(handle tp) {
     return (type_init_data *) (borrow<capsule>(handle(tp).attr("__nb_enum__"))).data();
 }