py: Add property object, with basic functionality.

Enabled by MICROPY_ENABLE_PROPERTY.

py/builtintables.c

@@ -31,6 +31,9 @@ STATIC const mp_map_elem_t mp_builtin_object_table[] = {
     { MP_OBJ_NEW_QSTR(MP_QSTR_list), (mp_obj_t)&mp_type_list },
     { MP_OBJ_NEW_QSTR(MP_QSTR_map), (mp_obj_t)&mp_type_map },
     { MP_OBJ_NEW_QSTR(MP_QSTR_object), (mp_obj_t)&mp_type_object },
+#if MICROPY_ENABLE_PROPERTY
+    { MP_OBJ_NEW_QSTR(MP_QSTR_property), (mp_obj_t)&mp_type_property },
+#endif
     { MP_OBJ_NEW_QSTR(MP_QSTR_set), (mp_obj_t)&mp_type_set },
     { MP_OBJ_NEW_QSTR(MP_QSTR_str), (mp_obj_t)&mp_type_str },
     { MP_OBJ_NEW_QSTR(MP_QSTR_super), (mp_obj_t)&mp_type_super },

py/mpconfig.h

@@ -135,6 +135,11 @@ typedef double mp_float_t;
 #define MICROPY_ENABLE_SLICE (1)
 #endif
 
+// Whether to support the property object
+#ifndef MICROPY_ENABLE_PROPERTY
+#define MICROPY_ENABLE_PROPERTY (0)
+#endif
+
 // Enable features which improve CPython compatibility
 // but may lead to more code size/memory usage.
 // TODO: Originally intended as generic category to not

py/obj.h

@@ -283,6 +283,7 @@ extern const mp_obj_type_t mp_type_fun_bc;
 extern const mp_obj_type_t mp_type_module;
 extern const mp_obj_type_t mp_type_staticmethod;
 extern const mp_obj_type_t mp_type_classmethod;
+extern const mp_obj_type_t mp_type_property;
 
 // Exceptions
 extern const mp_obj_type_t mp_type_BaseException;
@@ -518,6 +519,9 @@ typedef struct _mp_obj_static_class_method_t {
     mp_obj_t fun;
 } mp_obj_static_class_method_t;
 
+// property
+const mp_obj_t *mp_obj_property_get(mp_obj_t self_in);
+
 // sequence helpers
 void mp_seq_multiply(const void *items, uint item_sz, uint len, uint times, void *dest);
 bool m_seq_get_fast_slice_indexes(machine_uint_t len, mp_obj_t slice, machine_uint_t *begin, machine_uint_t *end);

py/objproperty.c

@@ -0,0 +1,95 @@
+#include <stdlib.h>
+#include <assert.h>
+
+#include "nlr.h"
+#include "misc.h"
+#include "mpconfig.h"
+#include "qstr.h"
+#include "obj.h"
+#include "runtime.h"
+
+#if MICROPY_ENABLE_PROPERTY
+
+typedef struct _mp_obj_property_t {
+    mp_obj_base_t base;
+    mp_obj_t proxy[3]; // getter, setter, deleter
+} mp_obj_property_t;
+
+STATIC mp_obj_t property_make_new(mp_obj_t type_in, uint n_args, uint n_kw, const mp_obj_t *args) {
+    // TODO check n_kw == 0
+
+    mp_obj_property_t *o = m_new_obj(mp_obj_property_t);
+    o->base.type = &mp_type_property;
+    if (n_args >= 5) {
+        nlr_raise(mp_obj_new_exception_msg_varg(&mp_type_TypeError, "property takes at most 4 arguments"));
+    }
+    if (n_args >= 4) {
+        // doc ignored
+    }
+    if (n_args >= 3) {
+        o->proxy[2] = args[2];
+    } else {
+        o->proxy[2] = mp_const_none;
+    }
+    if (n_args >= 2) {
+        o->proxy[1] = args[1];
+    } else {
+        o->proxy[1] = mp_const_none;
+    }
+    if (n_args >= 1) {
+        o->proxy[0] = args[0];
+    } else {
+        o->proxy[0] = mp_const_none;
+    }
+    return o;
+}
+
+STATIC mp_obj_t property_getter(mp_obj_t self_in, mp_obj_t getter) {
+    mp_obj_property_t *p2 = m_new_obj(mp_obj_property_t);
+    *p2 = *(mp_obj_property_t*)self_in;
+    p2->proxy[0] = getter;
+    return p2;
+}
+
+STATIC MP_DEFINE_CONST_FUN_OBJ_2(property_getter_obj, property_getter);
+
+STATIC mp_obj_t property_setter(mp_obj_t self_in, mp_obj_t setter) {
+    mp_obj_property_t *p2 = m_new_obj(mp_obj_property_t);
+    *p2 = *(mp_obj_property_t*)self_in;
+    p2->proxy[1] = setter;
+    return p2;
+}
+
+STATIC MP_DEFINE_CONST_FUN_OBJ_2(property_setter_obj, property_setter);
+
+STATIC mp_obj_t property_deleter(mp_obj_t self_in, mp_obj_t deleter) {
+    mp_obj_property_t *p2 = m_new_obj(mp_obj_property_t);
+    *p2 = *(mp_obj_property_t*)self_in;
+    p2->proxy[2] = deleter;
+    return p2;
+}
+
+STATIC MP_DEFINE_CONST_FUN_OBJ_2(property_deleter_obj, property_deleter);
+
+STATIC const mp_map_elem_t property_locals_dict_table[] = {
+    { MP_OBJ_NEW_QSTR(MP_QSTR_getter), (mp_obj_t)&property_getter_obj },
+    { MP_OBJ_NEW_QSTR(MP_QSTR_setter), (mp_obj_t)&property_setter_obj },
+    { MP_OBJ_NEW_QSTR(MP_QSTR_deleter), (mp_obj_t)&property_deleter_obj },
+};
+
+STATIC MP_DEFINE_CONST_DICT(property_locals_dict, property_locals_dict_table);
+
+const mp_obj_type_t mp_type_property = {
+    { &mp_type_type },
+    .name = MP_QSTR_property,
+    .make_new = property_make_new,
+    .locals_dict = (mp_obj_t)&property_locals_dict,
+};
+
+const mp_obj_t *mp_obj_property_get(mp_obj_t self_in) {
+    assert(MP_OBJ_IS_TYPE(self_in, &mp_type_property));
+    mp_obj_property_t *self = self_in;
+    return self->proxy;
+}
+
+#endif // MICROPY_ENABLE_PROPERTY

py/objtype.c

@@ -229,15 +229,35 @@ STATIC mp_obj_t class_binary_op(int op, mp_obj_t lhs_in, mp_obj_t rhs_in) {
 STATIC void class_load_attr(mp_obj_t self_in, qstr attr, mp_obj_t *dest) {
     // logic: look in obj members then class locals (TODO check this against CPython)
     mp_obj_class_t *self = self_in;
+
     mp_map_elem_t *elem = mp_map_lookup(&self->members, MP_OBJ_NEW_QSTR(attr), MP_MAP_LOOKUP);
     if (elem != NULL) {
         // object member, always treated as a value
+        // TODO should we check for properties?
         dest[0] = elem->value;
         return;
     }
+
     mp_obj_t member = mp_obj_class_lookup(self->base.type, attr);
     if (member != MP_OBJ_NULL) {
-        class_convert_return_attr(self_in, member, dest);
+        if (0) {
+#if MICROPY_ENABLE_PROPERTY
+        } else if (MP_OBJ_IS_TYPE(member, &mp_type_property)) {
+            // object member is a property
+            // delegate the store to the property
+            // TODO should this be part of class_convert_return_attr?
+            const mp_obj_t *proxy = mp_obj_property_get(member);
+            if (proxy[0] == mp_const_none) {
+                // TODO
+            } else {
+                dest[0] = mp_call_function_n_kw(proxy[0], 1, 0, &self_in);
+                // TODO should we convert the returned value using class_convert_return_attr?
+            }
+#endif
+        } else {
+            // not a property
+            class_convert_return_attr(self_in, member, dest);
+        }
         return;
     }
 
@@ -257,10 +277,30 @@ STATIC void class_load_attr(mp_obj_t self_in, qstr attr, mp_obj_t *dest) {
 
 STATIC bool class_store_attr(mp_obj_t self_in, qstr attr, mp_obj_t value) {
     mp_obj_class_t *self = self_in;
+
+#if MICROPY_ENABLE_PROPERTY
+    // for property, we need to do a lookup first in the class dict
+    // this makes all stores slow... how to fix?
+    mp_obj_t member = mp_obj_class_lookup(self->base.type, attr);
+    if (member != MP_OBJ_NULL && MP_OBJ_IS_TYPE(member, &mp_type_property)) {
+        // attribute already exists and is a property
+        // delegate the store to the property
+        const mp_obj_t *proxy = mp_obj_property_get(member);
+        if (proxy[1] == mp_const_none) {
+            // TODO better error message
+            return false;
+        } else {
+            mp_obj_t dest[2] = {self_in, value};
+            mp_call_function_n_kw(proxy[1], 2, 0, dest);
+            return true;
+        }
+    }
+#endif
+
     if (value == MP_OBJ_NULL) {
         // delete attribute
-        mp_map_elem_t *el = mp_map_lookup(&self->members, MP_OBJ_NEW_QSTR(attr), MP_MAP_LOOKUP_REMOVE_IF_FOUND);
-        return el != NULL;
+        mp_map_elem_t *elem = mp_map_lookup(&self->members, MP_OBJ_NEW_QSTR(attr), MP_MAP_LOOKUP_REMOVE_IF_FOUND);
+        return elem != NULL;
     } else {
         // store attribute
         mp_map_lookup(&self->members, MP_OBJ_NEW_QSTR(attr), MP_MAP_LOOKUP_ADD_IF_NOT_FOUND)->value = value;

py/py.mk

@@ -60,6 +60,7 @@ PY_O_BASENAME = \
 	objmap.o \
 	objmodule.o \
 	objobject.o \
+	objproperty.o \
 	objnone.o \
 	objnamedtuple.o \
 	objrange.o \

py/qstrdefs.h

@@ -281,3 +281,10 @@ Q(stdout)
 Q(stderr)
 Q(version_info)
 #endif
+
+#if MICROPY_ENABLE_PROPERTY
+Q(property)
+Q(getter)
+Q(setter)
+Q(deleter)
+#endif

unix/mpconfigport.h

@@ -10,6 +10,7 @@
 #define MICROPY_ENABLE_REPL_HELPERS (1)
 #define MICROPY_ENABLE_LEXER_UNIX   (1)
 #define MICROPY_ENABLE_SOURCE_LINE  (1)
+#define MICROPY_ENABLE_PROPERTY     (1)
 #define MICROPY_FLOAT_IMPL          (MICROPY_FLOAT_IMPL_DOUBLE)
 #define MICROPY_LONGINT_IMPL        (MICROPY_LONGINT_IMPL_MPZ)
 #define MICROPY_PATH_MAX            (PATH_MAX)