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| 1 | +/** A wrapper around [the JavaScript `Promise` class](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Promise) |
| 2 | +that exposes its functions in a type-safe and Swifty way. The `JSPromise` API is generic over both |
| 3 | +`Success` and `Failure` types, which improves compatibility with other statically-typed APIs such |
| 4 | +as Combine. If you don't know the exact type of your `Success` value, you should use `JSValue`, e.g. |
| 5 | +`JSPromise<JSValue, JSError>`. In the rare case, where you can't guarantee that the error thrown |
| 6 | +is of actual JavaScript `Error` type, you should use `JSPromise<JSValue, JSValue>`. |
| 7 | + |
| 8 | +This doesn't 100% match the JavaScript API, as `then` overload with two callbacks is not available. |
| 9 | +It's impossible to unify success and failure types from both callbacks in a single returned promise |
| 10 | +without type erasure. You should chain `then` and `catch` in those cases to avoid type erasure. |
| 11 | + |
| 12 | +**IMPORTANT**: instances of this class must have the same lifetime as the actual `Promise` object in |
| 13 | +the JavaScript environment, because callback handlers will be deallocated when `JSPromise.deinit` is |
| 14 | +executed. |
| 15 | + |
| 16 | +If the actual `Promise` object in JavaScript environment lives longer than this `JSPromise`, it may |
| 17 | +attempt to call a deallocated `JSClosure`. |
| 18 | +*/ |
| 19 | +public final class JSPromise<Success, Failure>: JSValueConvertible, JSValueConstructible { |
| 20 | + /// The underlying JavaScript `Promise` object. |
| 21 | + public let jsObject: JSObject |
| 22 | + |
| 23 | + private var callbacks = [JSClosure]() |
| 24 | + |
| 25 | + /// The underlying JavaScript `Promise` object wrapped as `JSValue`. |
| 26 | + public func jsValue() -> JSValue { |
| 27 | + .object(jsObject) |
| 28 | + } |
| 29 | + |
| 30 | + /// This private initializer assumes that the passed object is a JavaScript `Promise` |
| 31 | + private init(unsafe object: JSObject) { |
| 32 | + self.jsObject = object |
| 33 | + } |
| 34 | + |
| 35 | + /** Creates a new `JSPromise` instance from a given JavaScript `Promise` object. If `jsObject` |
| 36 | + is not an instance of JavaScript `Promise`, this initializer will return `nil`. |
| 37 | + */ |
| 38 | + public init?(_ jsObject: JSObject) { |
| 39 | + guard jsObject.isInstanceOf(JSObject.global.Promise.function!) else { return nil } |
| 40 | + self.jsObject = jsObject |
| 41 | + } |
| 42 | + |
| 43 | + /** Creates a new `JSPromise` instance from a given JavaScript `Promise` object. If `value` |
| 44 | + is not an object and is not an instance of JavaScript `Promise`, this function will |
| 45 | + return `nil`. |
| 46 | + */ |
| 47 | + public static func construct(from value: JSValue) -> Self? { |
| 48 | + guard case let .object(jsObject) = value else { return nil } |
| 49 | + return Self.init(jsObject) |
| 50 | + } |
| 51 | + |
| 52 | + /** Schedules the `success` closure to be invoked on sucessful completion of `self`. |
| 53 | + */ |
| 54 | + public func then(success: @escaping () -> ()) { |
| 55 | + let closure = JSClosure { _ in success() } |
| 56 | + callbacks.append(closure) |
| 57 | + _ = jsObject.then!(closure) |
| 58 | + } |
| 59 | + |
| 60 | + /** Schedules the `failure` closure to be invoked on either successful or rejected completion of |
| 61 | + `self`. |
| 62 | + */ |
| 63 | + public func finally(successOrFailure: @escaping () -> ()) -> Self { |
| 64 | + let closure = JSClosure { _ in |
| 65 | + successOrFailure() |
| 66 | + } |
| 67 | + callbacks.append(closure) |
| 68 | + return .init(unsafe: jsObject.finally!(closure).object!) |
| 69 | + } |
| 70 | + |
| 71 | + deinit { |
| 72 | + callbacks.forEach { $0.release() } |
| 73 | + } |
| 74 | +} |
| 75 | + |
| 76 | +extension JSPromise where Success == (), Failure == Never { |
| 77 | + /** Creates a new `JSPromise` instance from a given `resolver` closure. `resolver` takes |
| 78 | + a closure that your code should call to resolve this `JSPromise` instance. |
| 79 | + */ |
| 80 | + public convenience init(resolver: @escaping (@escaping () -> ()) -> ()) { |
| 81 | + let closure = JSClosure { arguments -> () in |
| 82 | + // The arguments are always coming from the `Promise` constructor, so we should be |
| 83 | + // safe to assume their type here |
| 84 | + resolver { arguments[0].function!() } |
| 85 | + } |
| 86 | + self.init(unsafe: JSObject.global.Promise.function!.new(closure)) |
| 87 | + callbacks.append(closure) |
| 88 | + } |
| 89 | +} |
| 90 | + |
| 91 | +extension JSPromise where Failure: JSValueConvertible { |
| 92 | + /** Creates a new `JSPromise` instance from a given `resolver` closure. `resolver` takes |
| 93 | + two closure that your code should call to either resolve or reject this `JSPromise` instance. |
| 94 | + */ |
| 95 | + public convenience init(resolver: @escaping (@escaping (Result<Success, JSError>) -> ()) -> ()) { |
| 96 | + let closure = JSClosure { arguments -> () in |
| 97 | + // The arguments are always coming from the `Promise` constructor, so we should be |
| 98 | + // safe to assume their type here |
| 99 | + let resolve = arguments[0].function! |
| 100 | + let reject = arguments[1].function! |
| 101 | + |
| 102 | + resolver { |
| 103 | + switch $0 { |
| 104 | + case .success: |
| 105 | + resolve() |
| 106 | + case let .failure(error): |
| 107 | + reject(error.jsValue()) |
| 108 | + } |
| 109 | + } |
| 110 | + } |
| 111 | + self.init(unsafe: JSObject.global.Promise.function!.new(closure)) |
| 112 | + callbacks.append(closure) |
| 113 | + } |
| 114 | +} |
| 115 | + |
| 116 | +extension JSPromise where Success: JSValueConvertible, Failure: JSError { |
| 117 | + /** Creates a new `JSPromise` instance from a given `resolver` closure. `resolver` takes |
| 118 | + a closure that your code should call to either resolve or reject this `JSPromise` instance. |
| 119 | + */ |
| 120 | + public convenience init(resolver: @escaping (@escaping (Result<Success, JSError>) -> ()) -> ()) { |
| 121 | + let closure = JSClosure { arguments -> () in |
| 122 | + // The arguments are always coming from the `Promise` constructor, so we should be |
| 123 | + // safe to assume their type here |
| 124 | + let resolve = arguments[0].function! |
| 125 | + let reject = arguments[1].function! |
| 126 | + |
| 127 | + resolver { |
| 128 | + switch $0 { |
| 129 | + case let .success(success): |
| 130 | + resolve(success.jsValue()) |
| 131 | + case let .failure(error): |
| 132 | + reject(error.jsValue()) |
| 133 | + } |
| 134 | + } |
| 135 | + } |
| 136 | + self.init(unsafe: JSObject.global.Promise.function!.new(closure)) |
| 137 | + callbacks.append(closure) |
| 138 | + } |
| 139 | +} |
| 140 | + |
| 141 | +extension JSPromise where Success: JSValueConstructible { |
| 142 | + /** Schedules the `success` closure to be invoked on sucessful completion of `self`. |
| 143 | + */ |
| 144 | + public func then( |
| 145 | + success: @escaping (Success) -> (), |
| 146 | + file: StaticString = #file, |
| 147 | + line: Int = #line |
| 148 | + ) { |
| 149 | + let closure = JSClosure { arguments -> () in |
| 150 | + guard let result = Success.construct(from: arguments[0]) else { |
| 151 | + fatalError("\(file):\(line): failed to unwrap success value for `then` callback") |
| 152 | + } |
| 153 | + success(result) |
| 154 | + } |
| 155 | + callbacks.append(closure) |
| 156 | + _ = jsObject.then!(closure) |
| 157 | + } |
| 158 | + |
| 159 | + /** Returns a new promise created from chaining the current `self` promise with the `success` |
| 160 | + closure invoked on sucessful completion of `self`. The returned promise will have a new |
| 161 | + `Success` type equal to the return type of `success`. |
| 162 | + */ |
| 163 | + public func then<ResultType: JSValueConvertible>( |
| 164 | + success: @escaping (Success) -> ResultType, |
| 165 | + file: StaticString = #file, |
| 166 | + line: Int = #line |
| 167 | + ) -> JSPromise<ResultType, Failure> { |
| 168 | + let closure = JSClosure { arguments -> JSValue in |
| 169 | + guard let result = Success.construct(from: arguments[0]) else { |
| 170 | + fatalError("\(file):\(line): failed to unwrap success value for `then` callback") |
| 171 | + } |
| 172 | + return success(result).jsValue() |
| 173 | + } |
| 174 | + callbacks.append(closure) |
| 175 | + return .init(unsafe: jsObject.then!(closure).object!) |
| 176 | + } |
| 177 | + |
| 178 | + /** Returns a new promise created from chaining the current `self` promise with the `success` |
| 179 | + closure invoked on sucessful completion of `self`. The returned promise will have a new type |
| 180 | + equal to the return type of `success`. |
| 181 | + */ |
| 182 | + public func then<ResultSuccess: JSValueConvertible, ResultFailure: JSValueConstructible>( |
| 183 | + success: @escaping (Success) -> JSPromise<ResultSuccess, ResultFailure>, |
| 184 | + file: StaticString = #file, |
| 185 | + line: Int = #line |
| 186 | + ) -> JSPromise<ResultSuccess, ResultFailure> { |
| 187 | + let closure = JSClosure { arguments -> JSValue in |
| 188 | + guard let result = Success.construct(from: arguments[0]) else { |
| 189 | + fatalError("\(file):\(line): failed to unwrap success value for `then` callback") |
| 190 | + } |
| 191 | + return success(result).jsValue() |
| 192 | + } |
| 193 | + callbacks.append(closure) |
| 194 | + return .init(unsafe: jsObject.then!(closure).object!) |
| 195 | + } |
| 196 | +} |
| 197 | + |
| 198 | +extension JSPromise where Failure: JSValueConstructible { |
| 199 | + /** Returns a new promise created from chaining the current `self` promise with the `failure` |
| 200 | + closure invoked on rejected completion of `self`. The returned promise will have a new `Success` |
| 201 | + type equal to the return type of the callback, while the `Failure` type becomes `Never`. |
| 202 | + */ |
| 203 | + public func `catch`<ResultSuccess: JSValueConvertible>( |
| 204 | + failure: @escaping (Failure) -> ResultSuccess, |
| 205 | + file: StaticString = #file, |
| 206 | + line: Int = #line |
| 207 | + ) -> JSPromise<ResultSuccess, Never> { |
| 208 | + let closure = JSClosure { arguments -> JSValue in |
| 209 | + guard let error = Failure.construct(from: arguments[0]) else { |
| 210 | + fatalError("\(file):\(line): failed to unwrap error value for `catch` callback") |
| 211 | + } |
| 212 | + return failure(error).jsValue() |
| 213 | + } |
| 214 | + callbacks.append(closure) |
| 215 | + return .init(unsafe: jsObject.then!(JSValue.undefined, closure).object!) |
| 216 | + } |
| 217 | + |
| 218 | + /** Schedules the `failure` closure to be invoked on rejected completion of `self`. |
| 219 | + */ |
| 220 | + public func `catch`( |
| 221 | + failure: @escaping (Failure) -> (), |
| 222 | + file: StaticString = #file, |
| 223 | + line: Int = #line |
| 224 | + ) { |
| 225 | + let closure = JSClosure { arguments -> () in |
| 226 | + guard let error = Failure.construct(from: arguments[0]) else { |
| 227 | + fatalError("\(file):\(line): failed to unwrap error value for `catch` callback") |
| 228 | + } |
| 229 | + failure(error) |
| 230 | + } |
| 231 | + callbacks.append(closure) |
| 232 | + _ = jsObject.then!(JSValue.undefined, closure) |
| 233 | + } |
| 234 | + |
| 235 | + /** Returns a new promise created from chaining the current `self` promise with the `failure` |
| 236 | + closure invoked on rejected completion of `self`. The returned promise will have a new type |
| 237 | + equal to the return type of `success`. |
| 238 | + */ |
| 239 | + public func `catch`<ResultSuccess: JSValueConvertible, ResultFailure: JSValueConstructible>( |
| 240 | + failure: @escaping (Failure) -> JSPromise<ResultSuccess, ResultFailure>, |
| 241 | + file: StaticString = #file, |
| 242 | + line: Int = #line |
| 243 | + ) -> JSPromise<ResultSuccess, ResultFailure> { |
| 244 | + let closure = JSClosure { arguments -> JSValue in |
| 245 | + guard let error = Failure.construct(from: arguments[0]) else { |
| 246 | + fatalError("\(file):\(line): failed to unwrap error value for `catch` callback") |
| 247 | + } |
| 248 | + return failure(error).jsValue() |
| 249 | + } |
| 250 | + callbacks.append(closure) |
| 251 | + return .init(unsafe: jsObject.then!(JSValue.undefined, closure).object!) |
| 252 | + } |
| 253 | +} |
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