Expose enum_ entries as new "__members__" attribute

docs/classes.rst

@@ -423,6 +423,12 @@ typed enums.
     >>> int(p.type)
     1L
 
+The entries defined by the enumeration type are exposed in the ``__members__`` property:
+
+.. code-block:: pycon
+
+    >>> Pet.Kind.__members__
+    {'Dog': Kind.Dog, 'Cat': Kind.Cat}
 
 .. note::
 

include/pybind11/pybind11.h

@@ -1116,24 +1116,32 @@ class class_ : public detail::generic_type {
 template <typename Type> class enum_ : public class_<Type> {
 public:
     using class_<Type>::def;
+    using class_<Type>::def_property_readonly_static;
     using Scalar = typename std::underlying_type<Type>::type;
     template <typename T> using arithmetic_tag = std::is_same<T, arithmetic>;
 
     template <typename... Extra>
     enum_(const handle &scope, const char *name, const Extra&... extra)
-      : class_<Type>(scope, name, extra...), m_parent(scope) {
+      : class_<Type>(scope, name, extra...), m_entries(), m_parent(scope) {
 
         constexpr bool is_arithmetic =
             !std::is_same<detail::first_of_t<arithmetic_tag, void, Extra...>,
                           void>::value;
 
-        auto entries = new std::unordered_map<Scalar, const char *>();
-        def("__repr__", [name, entries](Type value) -> std::string {
-            auto it = entries->find((Scalar) value);
-            return std::string(name) + "." +
-                ((it == entries->end()) ? std::string("???")
-                                        : std::string(it->second));
+        auto m_entries_ptr = m_entries.inc_ref().ptr();
+        def("__repr__", [name, m_entries_ptr](Type value) -> pybind11::str {
+            for (const auto &kv : reinterpret_borrow<dict>(m_entries_ptr)) {
+                if (pybind11::cast<Type>(kv.second) == value)
+                    return pybind11::str("{}.{}").format(name, kv.first);
+            }
+            return pybind11::str("{}.???").format(name);
         });
+        def_property_readonly_static("__members__", [m_entries_ptr](object /* self */) {
+            dict m;
+            for (const auto &kv : reinterpret_borrow<dict>(m_entries_ptr))
+                m[kv.first] = kv.second;
+            return m;
+        }, return_value_policy::copy);
         def("__init__", [](Type& value, Scalar i) { value = (Type)i; });
         def("__init__", [](Type& value, Scalar i) { new (&value) Type((Type) i); });
         def("__int__", [](Type value) { return (Scalar) value; });
@@ -1172,26 +1180,25 @@ template <typename Type> class enum_ : public class_<Type> {
         // Pickling and unpickling -- needed for use with the 'multiprocessing' module
         def("__getstate__", [](const Type &value) { return pybind11::make_tuple((Scalar) value); });
         def("__setstate__", [](Type &p, tuple t) { new (&p) Type((Type) t[0].cast<Scalar>()); });
-        m_entries = entries;
     }
 
     /// Export enumeration entries into the parent scope
-    enum_ &export_values() {
-        for (auto item : reinterpret_borrow<dict>(((PyTypeObject *) this->m_ptr)->tp_dict)) {
-            if (isinstance(item.second, this->m_ptr))
-                m_parent.attr(item.first) = item.second;
-        }
+    enum_& export_values() {
+        for (const auto &kv : m_entries)
+            m_parent.attr(kv.first) = kv.second;
         return *this;
     }
 
     /// Add an enumeration entry
     enum_& value(char const* name, Type value) {
-        this->attr(name) = pybind11::cast(value, return_value_policy::copy);
-        (*m_entries)[(Scalar) value] = name;
+        auto v = pybind11::cast(value, return_value_policy::copy);
+        this->attr(name) = v;
+        m_entries[pybind11::str(name)] = v;
         return *this;
     }
+
 private:
-    std::unordered_map<Scalar, const char *> *m_entries;
+    dict m_entries;
     handle m_parent;
 };
 

tests/test_enum.py

@@ -7,6 +7,15 @@ def test_unscoped_enum():
     assert str(UnscopedEnum.EOne) == "UnscopedEnum.EOne"
     assert str(UnscopedEnum.ETwo) == "UnscopedEnum.ETwo"
     assert str(EOne) == "UnscopedEnum.EOne"
+    # __members__ property
+    assert UnscopedEnum.__members__ == {"EOne": UnscopedEnum.EOne, "ETwo": UnscopedEnum.ETwo}
+    # __members__ readonly
+    with pytest.raises(AttributeError):
+        UnscopedEnum.__members__ = {}
+    # __members__ returns a copy
+    foo = UnscopedEnum.__members__
+    foo["bar"] = "baz"
+    assert UnscopedEnum.__members__ == {"EOne": UnscopedEnum.EOne, "ETwo": UnscopedEnum.ETwo}
 
     # no TypeError exception for unscoped enum ==/!= int comparisons
     y = UnscopedEnum.ETwo