This is a little bit of a patch (hack) I apply to allow the use of the descriptor protocol (or, most of it). Descriptors are really useful for reactive UI design, and easy to implement in a way that shares sensibilities with Transcrypt's implementation of properties. The readme suggested I start by raising the idea as an issue, so I didn't bother reworking it as a pull request that modifies the code-base directly. Hope this is interesting and doesn't wreck anything fundemental.
"""
Add the descriptor protocol to `py_metatype`.
Limitations:
- `__delete__` is not supported.
- Assigning a new value to an attribute that is a set operation on a class
will not replace the descriptor (much like Transcrypt's `@property`).
- Cannot access descriptor instance using `vars` (`vars` is not supported).
- Missing `__get__` or `__set__` are noop (much like Transcrypt's
`@property`).
"""
__pragma__('js', '{}', '''
(function(undefined) {
function _get_function(descriptor) {
return function() {
if(this.hasOwnProperty('__class__')) {
return descriptor.__get__(this, py_typeof(this))
} else {
return descriptor.__get__(null, this)
}
};
}
function _set_function(descriptor) {
return function(value) {
if(this.hasOwnProperty('__class__')) {
descriptor.__set__(this, value);
}
};
}
const _py_metatype_new = py_metatype.__new__;
py_metatype.__new__ = function (meta, name, bases, attributes) {
const new_type = _py_metatype_new(meta, name, bases, attributes);
for(const attribute in attributes) {
const descriptor = new_type[attribute];
if(
descriptor &&
descriptor.hasOwnProperty('__class__') &&
(descriptor.__get__ || descriptor.__set__)
) {
const data = { enumerable: true };
if(descriptor.__get__) {
data.get = _get_function(descriptor);
}
if(descriptor.__set__) {
data.set = _set_function(descriptor);
}
Object.defineProperty(new_type, attribute, data);
if(descriptor.__set_name__) {
descriptor.__set_name__(new_type, attribute);
}
}
}
return new_type;
};
})();
''')
This is a little bit of a patch (hack) I apply to allow the use of the descriptor protocol (or, most of it). Descriptors are really useful for reactive UI design, and easy to implement in a way that shares sensibilities with Transcrypt's implementation of properties. The readme suggested I start by raising the idea as an issue, so I didn't bother reworking it as a pull request that modifies the code-base directly. Hope this is interesting and doesn't wreck anything fundemental.