When + Parameter Packs (#1359)

Author: RomanPodymov

.github/workflows/ci.yml

@@ -17,7 +17,7 @@ concurrency:
 jobs:
   linux-build:
     name: Linux (Swift ${{ matrix.swift }})
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-22.04
     strategy:
       matrix:
         swift:

Sources/when.swift

@@ -110,6 +110,14 @@ public func when(fulfilled thenables: [any Thenable]) -> Promise<[Any]> {
 }
 #endif
 
+#if swift(>=5.9)
+public func when<each U: Thenable>(fulfilled: repeat each U) -> Promise<(repeat (each U).T)> {
+    var voidPromises: [Promise<Void>] = []
+    repeat voidPromises.append((each fulfilled).asVoid())
+    return _when(voidPromises).map(on: nil) { (repeat (each fulfilled).value!) }
+}
+#endif
+
 /// Wait for all promises in a set to fulfill.
 public func when<U: Thenable>(fulfilled promises: U...) -> Promise<Void> where U.T == Void {
     return _when(promises)

Tests/CorePromise/CancellableErrorTests.swift

@@ -100,13 +100,6 @@ class CancellationTests: XCTestCase {
     }
 
     func testDoesntCrashSwift() {
-      #if os(macOS)
-        // Previously exposed a bridging crash in Swift
-        // NOTE nobody was brave enough or diligent enough to report this to Apple :{
-        // NOTE no Linux test since this constructor doesn’t exist there
-        XCTAssertFalse(NSError().isCancelled)
-      #endif
-
       #if canImport(StoreKit)
         if #available(watchOS 6.2, *) {
             do {

Tests/CorePromise/RaceTests.swift

@@ -76,14 +76,17 @@ class RaceTests: XCTestCase {
     func testFulfilledWithNoWinner() {
         enum Error: Swift.Error { case test1, test2 }
         let ex = expectation(description: "")
-        let promises: [Promise<Int>] = [after(seconds: 1).map { _ in throw Error.test1 }, after(seconds: 2).map { _ in throw Error.test2 }]
+        let promises: [Promise<Int>] = [
+            after(seconds: 1).map { _ in throw Error.test1 },
+            after(seconds: 2).map { _ in throw Error.test2 }
+        ]
         race(fulfilled: promises).done { _ in
-            XCTFail()
+            XCTFail("Done with error")
             ex.fulfill()
         }.catch {
-            guard let pmkError = $0 as? PMKError else { return XCTFail() }
-            guard case .noWinner = pmkError else { return XCTFail() }
-            guard pmkError.debugDescription == "All thenables passed to race(fulfilled:) were rejected" else { return XCTFail() }
+            guard let pmkError = $0 as? PMKError else { return XCTFail("error is not PMKError") }
+            guard case .noWinner = pmkError else { return XCTFail("error is not .noWinner") }
+            guard pmkError.debugDescription == "All thenables passed to race(fulfilled:) were rejected" else { return XCTFail("Not all thenables passed to race(fulfilled:) were rejected") }
             ex.fulfill()
         }
         wait(for: [ex], timeout: 10)

Tests/CorePromise/WhenTests.swift

@@ -57,6 +57,25 @@ class WhenTests: XCTestCase {
         #endif
     }
 
+    func testParameterPacks() {
+        #if swift(>=5.9)
+        let e1 = expectation(description: "")
+        let p1 = Promise.value(1)
+        let g2 = Guarantee.value("Hello")
+        let p3 = Promise.value("world")
+        let g4 = Guarantee.value(2)
+
+        when(fulfilled: p1, g2, p3, g4).done { x1, x2, x3, x4 in
+            XCTAssertEqual(x1, 1)
+            XCTAssertEqual(x2, "Hello")
+            XCTAssertEqual(x3, "world")
+            XCTAssertEqual(x4, 2)
+            e1.fulfill()
+        }.silenceWarning()
+        waitForExpectations(timeout: 1, handler: nil)
+        #endif
+    }
+    
     func testDoubleTuple() {
         let e1 = expectation(description: "")
         let p1 = Promise.value(1)