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py: Add optional support for descriptors' __get__ and __set__ methods. 

Disabled by default.  Enabled on unix and windows ports.
This commit is contained in:
stijn 2015-02-14 18:43:54 +01:00 committed by Damien George
parent c260836beb
commit 28fa84b445
7 changed files with 99 additions and 23 deletions
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6
py/mpconfig.h
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@ -364,6 +364,12 @@ typedef double mp_float_t;
#define MICROPY_PY_FUNCTION_ATTRS (0)
#endif
// Whether to support descriptors (__get__ and __set__)
// This costs some code size and makes all load attrs and store attrs slow
#ifndef MICROPY_PY_DESCRIPTORS
#define MICROPY_PY_DESCRIPTORS (0)
#endif
// Whether str object is proper unicode
#ifndef MICROPY_PY_BUILTINS_STR_UNICODE
#define MICROPY_PY_BUILTINS_STR_UNICODE (0)

67
py/objtype.c
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@ -463,16 +463,34 @@ void mp_obj_instance_load_attr(mp_obj_t self_in, qstr attr, mp_obj_t *dest) {
if (member != MP_OBJ_NULL) {
#if MICROPY_PY_BUILTINS_PROPERTY
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 mp_convert_member_lookup?
// object member is a property; delegate the load to the property
// Note: This is an optimisation for code size and execution time.
// The proper way to do it is have the functionality just below
// in a __get__ method of the property object, and then it would
// be called by the descriptor code down below. But that way
// requires overhead for the nested mp_call's and overhead for
// the code.
const mp_obj_t *proxy = mp_obj_property_get(member);
if (proxy[0] == mp_const_none) {
// TODO
nlr_raise(mp_obj_new_exception_msg(&mp_type_AttributeError, "unreadable attribute"));
} else {
dest[0] = mp_call_function_n_kw(proxy[0], 1, 0, &self_in);
// TODO should we convert the returned value using mp_convert_member_lookup?
}
return;
}
#endif
#if MICROPY_PY_DESCRIPTORS
// found a class attribute; if it has a __get__ method then call it with the
// class instance and class as arguments and return the result
// Note that this is functionally correct but very slow: each load_attr
// requires an extra mp_load_method_maybe to check for the __get__.
mp_obj_t attr_get_method[4];
mp_load_method_maybe(member, MP_QSTR___get__, attr_get_method);
if (attr_get_method[0] != MP_OBJ_NULL) {
attr_get_method[2] = self_in;
attr_get_method[3] = mp_obj_get_type(self_in);
dest[0] = mp_call_method_n_kw(2, 0, attr_get_method);
}
#endif
return;
@ -495,9 +513,11 @@ void mp_obj_instance_load_attr(mp_obj_t self_in, qstr attr, mp_obj_t *dest) {
bool mp_obj_instance_store_attr(mp_obj_t self_in, qstr attr, mp_obj_t value) {
mp_obj_instance_t *self = self_in;
#if MICROPY_PY_BUILTINS_PROPERTY
// for property, we need to do a lookup first in the class dict
// this makes all stores slow... how to fix?
#if MICROPY_PY_BUILTINS_PROPERTY || MICROPY_PY_DESCRIPTORS
// With property and/or descriptors enabled we need to do a lookup
// first in the class dict for the attribute to see if the store should
// be delegated.
// Note: this makes all stores slow... how to fix?
mp_obj_t member[2] = {MP_OBJ_NULL};
struct class_lookup_data lookup = {
.obj = self,
@ -507,12 +527,20 @@ bool mp_obj_instance_store_attr(mp_obj_t self_in, qstr attr, mp_obj_t value) {
.is_type = false,
};
mp_obj_class_lookup(&lookup, self->base.type);
if (member[0] != MP_OBJ_NULL && MP_OBJ_IS_TYPE(member[0], &mp_type_property)) {
// attribute already exists and is a property
// delegate the store to the property
if (member[0] != MP_OBJ_NULL) {
#if MICROPY_PY_BUILTINS_PROPERTY
if (MP_OBJ_IS_TYPE(member[0], &mp_type_property)) {
// attribute exists and is a property; delegate the store
// Note: This is an optimisation for code size and execution time.
// The proper way to do it is have the functionality just below
// in a __set__ method of the property object, and then it would
// be called by the descriptor code down below. But that way
// requires overhead for the nested mp_call's and overhead for
// the code.
const mp_obj_t *proxy = mp_obj_property_get(member[0]);
if (proxy[1] == mp_const_none) {
// TODO better error message
// TODO better error message?
return false;
} else {
mp_obj_t dest[2] = {self_in, value};
@ -522,6 +550,21 @@ bool mp_obj_instance_store_attr(mp_obj_t self_in, qstr attr, mp_obj_t value) {
}
#endif
#if MICROPY_PY_DESCRIPTORS
// found a class attribute; if it has a __set__ method then call it with the
// class instance and value as arguments
mp_obj_t attr_set_method[4];
mp_load_method_maybe(member[0], MP_QSTR___set__, attr_set_method);
if (attr_set_method[0] != MP_OBJ_NULL) {
attr_set_method[2] = self_in;
attr_set_method[3] = value;
mp_call_method_n_kw(2, 0, attr_set_method);
return true;
}
#endif
}
#endif
if (value == MP_OBJ_NULL) {
// delete attribute
mp_map_elem_t *elem = mp_map_lookup(&self->members, MP_OBJ_NEW_QSTR(attr), MP_MAP_LOOKUP_REMOVE_IF_FOUND);

4
py/qstrdefs.h
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@ -66,6 +66,10 @@ Q(__add__)
Q(__sub__)
Q(__repr__)
Q(__str__)
#if MICROPY_PY_DESCRIPTORS
Q(__get__)
Q(__set__)
#endif
Q(__getattr__)
Q(__del__)
Q(__call__)

5
py/vm.c
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@ -393,8 +393,9 @@ dispatch_loop:
DISPATCH();
}
#else
// This caching code works with MICROPY_PY_BUILTINS_PROPERTY enabled because
// if the attr exists in self->members then it can't be a property. A
// This caching code works with MICROPY_PY_BUILTINS_PROPERTY and/or
// MICROPY_PY_DESCRIPTORS enabled because if the attr exists in
// self->members then it can't be a property or have descriptors. A
// consequence of this is that we can't use MP_MAP_LOOKUP_ADD_IF_NOT_FOUND
// in the fast-path below, because that store could override a property.
ENTRY(MP_BC_STORE_ATTR): {

20
tests/basics/class_descriptor.py Normal file
View File

@ -0,0 +1,20 @@
class Descriptor:
def __get__(self, obj, cls):
print(type(obj) is Main)
print(cls is Main)
return 'result'
def __set__(self, obj, val):
print(type(obj) is Main)
print(val)
class Main:
Forward = Descriptor()
m = Main()
r = m.Forward
if 'Descriptor' in repr(r.__class__):
print('SKIP')
else:
print(r)
m.Forward = 'a'

1
unix/mpconfigport.h
View File

@ -58,6 +58,7 @@
#define MICROPY_OPT_CACHE_MAP_LOOKUP_IN_BYTECODE (1)
#define MICROPY_CAN_OVERRIDE_BUILTINS (1)
#define MICROPY_PY_FUNCTION_ATTRS (1)
#define MICROPY_PY_DESCRIPTORS (1)
#define MICROPY_PY_BUILTINS_STR_UNICODE (1)
#define MICROPY_PY_BUILTINS_MEMORYVIEW (1)
#define MICROPY_PY_BUILTINS_FROZENSET (1)

1
windows/mpconfigport.h
View File

@ -51,6 +51,7 @@
#define MICROPY_STREAMS_NON_BLOCK (1)
#define MICROPY_OPT_COMPUTED_GOTO (0)
#define MICROPY_CAN_OVERRIDE_BUILTINS (1)
#define MICROPY_PY_DESCRIPTORS (1)
#define MICROPY_PY_BUILTINS_STR_UNICODE (1)
#define MICROPY_PY_BUILTINS_MEMORYVIEW (1)
#define MICROPY_PY_BUILTINS_FROZENSET (1)