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py/objtype: Implement better support for overriding native's __init__. 

This patch cleans up and generalises part of the code which handles
overriding and calling a native base-class's __init__ method.  It defers
the call to the native make_new() function until after the user (Python)
__init__() method has run.  That user method now has the chance to call the
native __init__/make_new and pass it different arguments.  If the user
doesn't call the super().__init__ method then it will be called
automatically after the user code finishes, to finalise construction of the
instance.
This commit is contained in:
Damien George 2017-11-30 10:31:42 +11:00
parent d3f82bc425
commit d32d22dfd7
2 changed files with 64 additions and 29 deletions
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15
py/objexcept.c
View File

@ -212,27 +212,12 @@ STATIC void exception_attr(mp_obj_t self_in, qstr attr, mp_obj_t *dest) {
}
}
STATIC mp_obj_t exc___init__(size_t n_args, const mp_obj_t *args) {
mp_obj_exception_t *self = MP_OBJ_TO_PTR(args[0]);
mp_obj_t argst = mp_obj_new_tuple(n_args - 1, args + 1);
self->args = MP_OBJ_TO_PTR(argst);
return mp_const_none;
}
STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(exc___init___obj, 1, MP_OBJ_FUN_ARGS_MAX, exc___init__);
STATIC const mp_rom_map_elem_t exc_locals_dict_table[] = {
{ MP_ROM_QSTR(MP_QSTR___init__), MP_ROM_PTR(&exc___init___obj) },
};
STATIC MP_DEFINE_CONST_DICT(exc_locals_dict, exc_locals_dict_table);
const mp_obj_type_t mp_type_BaseException = {
{ &mp_type_type },
.name = MP_QSTR_BaseException,
.print = mp_obj_exception_print,
.make_new = mp_obj_exception_make_new,
.attr = exception_attr,
.locals_dict = (mp_obj_dict_t*)&exc_locals_dict,
};
#define MP_DEFINE_EXCEPTION(exc_name, base_name) \

74
py/objtype.c
View File

@ -46,14 +46,6 @@ STATIC mp_obj_t static_class_method_make_new(const mp_obj_type_t *self_in, size_
/******************************************************************************/
// instance object
STATIC mp_obj_t mp_obj_new_instance(const mp_obj_type_t *class, size_t subobjs) {
mp_obj_instance_t *o = m_new_obj_var(mp_obj_instance_t, mp_obj_t, subobjs);
o->base.type = class;
mp_map_init(&o->members, 0);
mp_seq_clear(o->subobj, 0, subobjs, sizeof(*o->subobj));
return MP_OBJ_FROM_PTR(o);
}
STATIC int instance_count_native_bases(const mp_obj_type_t *type, const mp_obj_type_t **last_native_base) {
int count = 0;
for (;;) {
@ -87,6 +79,30 @@ STATIC int instance_count_native_bases(const mp_obj_type_t *type, const mp_obj_t
}
}
// This wrapper function is allows a subclass of a native type to call the
// __init__() method (corresponding to type->make_new) of the native type.
STATIC mp_obj_t native_base_init_wrapper(size_t n_args, const mp_obj_t *args) {
mp_obj_instance_t *self = MP_OBJ_TO_PTR(args[0]);
const mp_obj_type_t *native_base = NULL;
instance_count_native_bases(self->base.type, &native_base);
self->subobj[0] = native_base->make_new(native_base, n_args - 1, 0, args + 1);
return mp_const_none;
}
STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(native_base_init_wrapper_obj, 1, MP_OBJ_FUN_ARGS_MAX, native_base_init_wrapper);
STATIC mp_obj_t mp_obj_new_instance(const mp_obj_type_t *class, size_t subobjs) {
mp_obj_instance_t *o = m_new_obj_var(mp_obj_instance_t, mp_obj_t, subobjs);
o->base.type = class;
mp_map_init(&o->members, 0);
// Initialise the native base-class slot (should be 1 at most) with a valid
// object. It doesn't matter which object, so long as it can be uniquely
// distinguished from a native class that is initialised.
if (subobjs != 0) {
o->subobj[0] = MP_OBJ_FROM_PTR(&native_base_init_wrapper_obj);
}
return MP_OBJ_FROM_PTR(o);
}
// TODO
// This implements depth-first left-to-right MRO, which is not compliant with Python3 MRO
// http://python-history.blogspot.com/2010/06/method-resolution-order.html
@ -280,7 +296,13 @@ mp_obj_t mp_obj_instance_make_new(const mp_obj_type_t *self, size_t n_args, size
if (init_fn[0] == MP_OBJ_SENTINEL) {
// Native type's constructor is what wins - it gets all our arguments,
// and none Python classes are initialized at all.
o->subobj[0] = native_base->make_new(native_base, n_args, n_kw, args);
// Since type->make_new() implements both __new__() and __init__() in
// one go, of which the latter may be overridden by the Python subclass,
// we defer (see the end of this function) the call of the native
// constructor to give a chance for the Python __init__() method to call
// said native constructor.
} else if (init_fn[0] != MP_OBJ_NULL) {
// now call Python class __new__ function with all args
if (n_args == 0 && n_kw == 0) {
@ -305,6 +327,8 @@ mp_obj_t mp_obj_instance_make_new(const mp_obj_type_t *self, size_t n_args, size
o = MP_OBJ_TO_PTR(new_ret);
// now call Python class __init__ function with all args
// This method has a chance to call super().__init__() to construct a
// possible native base class.
init_fn[0] = init_fn[1] = MP_OBJ_NULL;
lookup.obj = o;
lookup.attr = MP_QSTR___init__;
@ -333,6 +357,12 @@ mp_obj_t mp_obj_instance_make_new(const mp_obj_type_t *self, size_t n_args, size
}
// If the type had a native base that was not explicitly initialised
// (constructed) by the Python __init__() method then construct it now.
if (native_base != NULL && o->subobj[0] == MP_OBJ_FROM_PTR(&native_base_init_wrapper_obj)) {
o->subobj[0] = native_base->make_new(native_base, n_args, n_kw, args);
}
return MP_OBJ_FROM_PTR(o);
}
@ -1107,6 +1137,11 @@ STATIC void super_attr(mp_obj_t self_in, qstr attr, mp_obj_t *dest) {
.is_type = false,
};
// Allow a call super().__init__() to reach any native base classes
if (attr == MP_QSTR___init__) {
lookup.meth_offset = offsetof(mp_obj_type_t, make_new);
}
if (type->parent == NULL) {
// no parents, do nothing
#if MICROPY_MULTIPLE_INHERITANCE
@ -1116,18 +1151,33 @@ STATIC void super_attr(mp_obj_t self_in, qstr attr, mp_obj_t *dest) {
const mp_obj_t *items = parent_tuple->items;
for (size_t i = 0; i < len; i++) {
assert(MP_OBJ_IS_TYPE(items[i], &mp_type_type));
if (MP_OBJ_TO_PTR(items[i]) == &mp_type_object) {
// The "object" type will be searched at the end of this function,
// and we don't want to lookup native methods in object.
continue;
}
mp_obj_class_lookup(&lookup, (mp_obj_type_t*)MP_OBJ_TO_PTR(items[i]));
if (dest[0] != MP_OBJ_NULL) {
return;
break;
}
}
#endif
} else {
} else if (type->parent != &mp_type_object) {
mp_obj_class_lookup(&lookup, type->parent);
}
if (dest[0] != MP_OBJ_NULL) {
if (dest[0] == MP_OBJ_SENTINEL) {
// Looked up native __init__ so defer to it
dest[0] = MP_OBJ_FROM_PTR(&native_base_init_wrapper_obj);
dest[1] = self->obj;
}
return;
}
}
// Reset meth_offset so we don't look up any native methods in object,
// because object never takes up the native base-class slot.
lookup.meth_offset = 0;
mp_obj_class_lookup(&lookup, &mp_type_object);
}