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Add init(unsafelyCopying:JSObject) on @JS struct #510
Description
The goal is to support the following code
import JavaScriptKit
@JS protocol JSON {
func parse(_ message: String) throws(JSException) -> JSObject
func serialize(_ message: JSObject) throws(JSException) -> String
}
@JSGetter(from: .global) var json: JSON
@JS struct ShoppingCart {
var x: Int
@JS public func toJSON() throws(JSException) -> String {
json.serialize(self.toJSObject())
}
@JS static public func fromJSON(_ string: String) throws(JSException) -> ShoppingCart {
self.init(unsafelyCopying: json.parse(string))
}
/* Generated by ExportSwift
init(unsafelyCopying jsObject: JSObject) {
_ShoppingCartHelpers.lower(jsObject)
self = bridgeJSLiftParameter()
}
func toJSObject() -> JSObject {
_ShoppingCartHelpers.raise(...)
return bridgeJSLowerReturn()
}
*/
}Future direction
There's an opinion that such struct should follow value semantics, for which it has to copy its property values out to Wasm linear memory out of JS. To control copying strategies we might consider adding an argument to @JS controlling this, i.e. @JS(copy: .lazy), @JS(copy: .eager).
In the long term we should also support @JS struct Foo: ~Copyable that avoids copies altogether and always gives access to backing JS object reference.
Activity
[-]Make `init(unsafelyWrapping:JSObject` available on `@JS struct` declarations[/-][+]Make `init(unsafelyWrapping:JSObject` available on `@JS struct`[/+][-]Make `init(unsafelyWrapping:JSObject` available on `@JS struct`[/-][+]Make `init(unsafelyWrapping:JSObject)` available on `@JS struct`[/+][-]Make `init(unsafelyWrapping:JSObject)` available on `@JS struct`[/-][+]Add `init(unsafelyWrapping:JSObject)` on `@JS struct`[/+][-]Add `init(unsafelyWrapping:JSObject)` on `@JS struct`[/-][+]Add `init(unsafelyCopying:JSObject)` on `@JS struct`[/+]