refactor: replace .get_type with type::handle_of (#2492)

* refactor: replace .get_type with type::handle_of

* refactor: use impl for handle_of

* fix: deprecate h.get_type()

docs/changelog.rst

@@ -17,10 +17,16 @@ See :ref:`upgrade-guide-2.6` for help upgrading to the new version.
   This reduces binary size quite substantially (~25%).
   `#2463 <https://github.com/pybind/pybind11/pull/2463>`_
 
-* Keyword-only argument supported in Python 2 or 3 with ``py::kw_only()``.
+* Keyword-only arguments supported in Python 2 or 3 with ``py::kw_only()``.
   `#2100 <https://github.com/pybind/pybind11/pull/2100>`_
 
-* Positional-only argument supported in Python 2 or 3 with ``py::pos_only()``.
+* Positional-only arguments supported in Python 2 or 3 with ``py::pos_only()``.
+  `#2459 <https://github.com/pybind/pybind11/pull/2459>`_
+
+* Access to the type object now provided with ``py::type::of<T>()`` and
+  ``py::type::of(h)``.
+  `#2364 <https://github.com/pybind/pybind11/pull/2364>`_
+
 
 * Perfect forwarding support for methods.
   `#2048 <https://github.com/pybind/pybind11/pull/2048>`_

docs/upgrade.rst

@@ -17,6 +17,9 @@ An error is now thrown when ``__init__`` is forgotten on subclasses. This was
 incorrect before, but was not checked. Add a call to ``__init__`` if it is
 missing.
 
+The undocumented ``h.get_type()`` method has been deprecated and replaced by
+``py::type::of(h)``.
+
 If ``__eq__`` defined but not ``__hash__``, ``__hash__`` is now set to
 ``None``, as in normal CPython. You should add ``__hash__`` if you intended the
 class to be hashable, possibly using the new ``py::hash`` shortcut.

include/pybind11/cast.h

@@ -636,7 +636,7 @@ public:
     /// native typeinfo, or when the native one wasn't able to produce a value.
     PYBIND11_NOINLINE bool try_load_foreign_module_local(handle src) {
         constexpr auto *local_key = PYBIND11_MODULE_LOCAL_ID;
-        const auto pytype = src.get_type();
+        const auto pytype = type::handle_of(src);
         if (!hasattr(pytype, local_key))
             return false;
 
@@ -1130,7 +1130,7 @@ public:
         }
 
         /* Check if this is a C++ type */
-        auto &bases = all_type_info((PyTypeObject *) h.get_type().ptr());
+        auto &bases = all_type_info((PyTypeObject *) type::handle_of(h).ptr());
         if (bases.size() == 1) { // Only allowing loading from a single-value type
             value = values_and_holders(reinterpret_cast<instance *>(h.ptr())).begin()->value_ptr();
             return true;
@@ -1708,7 +1708,7 @@ template <typename T, typename SFINAE> type_caster<T, SFINAE> &load_type(type_ca
         throw cast_error("Unable to cast Python instance to C++ type (compile in debug mode for details)");
 #else
         throw cast_error("Unable to cast Python instance of type " +
-            (std::string) str(handle.get_type()) + " to C++ type '" + type_id<T>() + "'");
+            (std::string) str(type::handle_of(handle)) + " to C++ type '" + type_id<T>() + "'");
 #endif
     }
     return conv;
@@ -1759,7 +1759,7 @@ detail::enable_if_t<!detail::move_never<T>::value, T> move(object &&obj) {
         throw cast_error("Unable to cast Python instance to C++ rvalue: instance has multiple references"
             " (compile in debug mode for details)");
 #else
-        throw cast_error("Unable to move from Python " + (std::string) str(obj.get_type()) +
+        throw cast_error("Unable to move from Python " + (std::string) str(type::handle_of(obj)) +
                 " instance to C++ " + type_id<T>() + " instance: instance has multiple references");
 #endif
 
@@ -2206,13 +2206,13 @@ PYBIND11_NAMESPACE_END(detail)
 
 
 template<typename T>
-type type::of() {
+handle type::handle_of() {
    static_assert(
       std::is_base_of<detail::type_caster_generic, detail::make_caster<T>>::value,
       "py::type::of<T> only supports the case where T is a registered C++ types."
     );
 
-    return type((PyObject*) detail::get_type_handle(typeid(T), true).ptr(), borrowed_t());
+    return detail::get_type_handle(typeid(T), true);
 }
 
 

include/pybind11/eigen.h

@@ -553,7 +553,7 @@ struct type_caster<Type, enable_if_t<is_eigen_sparse<Type>::value>> {
         object matrix_type = sparse_module.attr(
             rowMajor ? "csr_matrix" : "csc_matrix");
 
-        if (!obj.get_type().is(matrix_type)) {
+        if (!type::handle_of(obj).is(matrix_type)) {
             try {
                 obj = matrix_type(obj);
             } catch (const error_already_set &) {

include/pybind11/pybind11.h

@@ -1489,7 +1489,7 @@ struct enum_base {
 
         m_base.attr("__repr__") = cpp_function(
             [](handle arg) -> str {
-                handle type = arg.get_type();
+                handle type = type::handle_of(arg);
                 object type_name = type.attr("__name__");
                 dict entries = type.attr("__entries");
                 for (const auto &kv : entries) {
@@ -1503,7 +1503,7 @@ struct enum_base {
 
         m_base.attr("name") = property(cpp_function(
             [](handle arg) -> str {
-                dict entries = arg.get_type().attr("__entries");
+                dict entries = type::handle_of(arg).attr("__entries");
                 for (const auto &kv : entries) {
                     if (handle(kv.second[int_(0)]).equal(arg))
                         return pybind11::str(kv.first);
@@ -1542,7 +1542,7 @@ struct enum_base {
         #define PYBIND11_ENUM_OP_STRICT(op, expr, strict_behavior)                     \
             m_base.attr(op) = cpp_function(                                            \
                 [](object a, object b) {                                               \
-                    if (!a.get_type().is(b.get_type()))                                \
+                    if (!type::handle_of(a).is(type::handle_of(b)))                    \
                         strict_behavior;                                               \
                     return expr;                                                       \
                 },                                                                     \
@@ -2115,7 +2115,7 @@ inline function get_type_override(const void *this_ptr, const type_info *this_ty
     handle self = get_object_handle(this_ptr, this_type);
     if (!self)
         return function();
-    handle type = self.get_type();
+    handle type = type::handle_of(self);
     auto key = std::make_pair(type.ptr(), name);
 
     /* Cache functions that aren't overridden in Python to avoid

include/pybind11/pytypes.h

@@ -152,7 +152,8 @@ public:
 
     /// Return the object's current reference count
     int ref_count() const { return static_cast<int>(Py_REFCNT(derived().ptr())); }
-    /// Return a handle to the Python type object underlying the instance
+
+    PYBIND11_DEPRECATED("Call py::type::handle_of(h) or py::type::of(h) instead of h.get_type()")
     handle get_type() const;
 
 private:
@@ -897,13 +898,24 @@ class type : public object {
 public:
     PYBIND11_OBJECT(type, object, PyType_Check)
 
-    static type of(handle h) { return type((PyObject*) Py_TYPE(h.ptr()), borrowed_t{}); }
+    /// Return a type handle from a handle or an object
+    static handle handle_of(handle h) { return handle((PyObject*) Py_TYPE(h.ptr())); }
+
+    /// Return a type object from a handle or an object
+    static type of(handle h) { return type(type::handle_of(h), borrowed_t{}); }
+
+    // Defined in pybind11/cast.h
+    /// Convert C++ type to handle if previously registered. Does not convert
+    /// standard types, like int, float. etc. yet.
+    /// See https://github.com/pybind/pybind11/issues/2486
+    template<typename T>
+    static handle handle_of();
 
-    /// Convert C++ type to py::type if previously registered. Does not convert
-    // standard types, like int, float. etc. yet.
-    // See https://github.com/pybind/pybind11/issues/2486
+    /// Convert C++ type to type if previously registered. Does not convert
+    /// standard types, like int, float. etc. yet.
+    /// See https://github.com/pybind/pybind11/issues/2486
     template<typename T>
-    static type of();
+    static type of() {return type(type::handle_of<T>(), borrowed_t{}); }
 };
 
 class iterable : public object {
@@ -1568,7 +1580,8 @@ template <typename D>
 str_attr_accessor object_api<D>::doc() const { return attr("__doc__"); }
 
 template <typename D>
-handle object_api<D>::get_type() const { return (PyObject *) Py_TYPE(derived().ptr()); }
+PYBIND11_DEPRECATED("Use py::type::of(h) instead of h.get_type()")
+handle object_api<D>::get_type() const { return type::handle_of(*this); }
 
 template <typename D>
 bool object_api<D>::rich_compare(object_api const &other, int value) const {