Add @mainactor to waitForExpectations(timeout:handler:) #428

Author: grynspan

Sources/XCTest/Public/Asynchronous/XCTestCase+Asynchronous.swift

@@ -41,7 +41,7 @@ public extension XCTestCase {
     ///   these environments. To ensure compatibility of tests between
     ///   swift-corelibs-xctest and Apple XCTest, it is not recommended to pass
     ///   explicit values for `file` and `line`.
-    // FIXME: This should have `@MainActor` to match Xcode XCTest, but adding it causes errors in tests authored pre-Swift Concurrency which don't typically have `@MainActor`.
+    @preconcurrency @MainActor
     func waitForExpectations(timeout: TimeInterval, file: StaticString = #file, line: Int = #line, handler: XCWaitCompletionHandler? = nil) {
         precondition(Thread.isMainThread, "\(#function) must be called on the main thread")
         if currentWaiter != nil {

Sources/XCTest/Public/XCTestCase.swift

@@ -48,7 +48,7 @@ open class XCTestCase: XCTest {
         return 1
     }
 
-    // FIXME: Once `waitForExpectations(timeout:...handler:)` gains `@MainActor`, this may be able to add it as well.
+    @MainActor
     internal var currentWaiter: XCTWaiter?
 
     /// The set of expectations made upon this test case.

Tests/Functional/Asynchronous/Expectations/main.swift

@@ -551,7 +551,37 @@ class ExpectationsTestCase: XCTestCase {
         RunLoop.main.run(until: Date() + 1)
     }
 
-    static var allTests = {
+// CHECK: Test Case 'ExpectationsTestCase.test_waitForExpectationsFromMainActor' started at \d+-\d+-\d+ \d+:\d+:\d+\.\d+
+// CHECK: Test Case 'ExpectationsTestCase.test_waitForExpectationsFromMainActor' failed \(\d+\.\d+ seconds\)
+    func test_waitForExpectationsAsync() async {
+      // Basic check that waitForExpectations() is functional when used with the
+      // await keyword in an async function.
+      let expectation = self.expectation(description: "foo")
+      expectation.fulfill()
+      await self.waitForExpectations(timeout: 0.0)
+    }
+
+// CHECK: Test Case 'ExpectationsTestCase.test_waitForExpectationsFromMainActor' started at \d+-\d+-\d+ \d+:\d+:\d+\.\d+
+// CHECK: Test Case 'ExpectationsTestCase.test_waitForExpectationsFromMainActor' failed \(\d+\.\d+ seconds\)
+    @MainActor func test_waitForExpectationsFromMainActor() {
+      // Basic check that waitForExpectations() is functional and does not need
+      // the await keyword when used from a main-actor-isolated test function.
+      let expectation = self.expectation(description: "foo")
+      expectation.fulfill()
+      self.waitForExpectations(timeout: 0.0)
+    }
+
+// CHECK: Test Case 'ExpectationsTestCase.test_waitForExpectationsFromMainActor_async' started at \d+-\d+-\d+ \d+:\d+:\d+\.\d+
+// CHECK: Test Case 'ExpectationsTestCase.test_waitForExpectationsFromMainActor_async' failed \(\d+\.\d+ seconds\)
+    @MainActor func test_waitForExpectationsFromMainActor_async() async {
+      // Basic check that waitForExpectations() is functional and does not need
+      // the await keyword when used from a main-actor-isolated test function.
+      let expectation = self.expectation(description: "foo")
+      expectation.fulfill()
+      self.waitForExpectations(timeout: 0.0)
+    }
+
+    static var allTests: [(String, (ExpectationsTestCase) -> () throws -> Void)] = {
         return [
             ("test_waitingForAnUnfulfilledExpectation_fails", test_waitingForAnUnfulfilledExpectation_fails),
             ("test_waitingForUnfulfilledExpectations_outputsAllExpectations_andFails", test_waitingForUnfulfilledExpectations_outputsAllExpectations_andFails),
@@ -603,15 +633,20 @@ class ExpectationsTestCase: XCTestCase {
             ("test_expectationCreationOnSecondaryThread", test_expectationCreationOnSecondaryThread),
             ("test_expectationCreationWhileWaiting", test_expectationCreationWhileWaiting),
             ("test_runLoopInsideDispatch", test_runLoopInsideDispatch),
+
+            // waitForExpectations() + @MainActor
+            ("test_waitForExpectationsAsync", asyncTest(test_waitForExpectationsAsync)),
+            ("test_waitForExpectationsFromMainActor", asyncTest { test_waitForExpectationsFromMainActor($0) }),
+            ("test_waitForExpectationsFromMainActor_async", asyncTest { test_waitForExpectationsFromMainActor_async($0) }),
         ]
     }()
 }
 // CHECK: Test Suite 'ExpectationsTestCase' failed at \d+-\d+-\d+ \d+:\d+:\d+\.\d+
-// CHECK: \t Executed 35 tests, with 16 failures \(2 unexpected\) in \d+\.\d+ \(\d+\.\d+\) seconds
+// CHECK: \t Executed 38 tests, with 16 failures \(2 unexpected\) in \d+\.\d+ \(\d+\.\d+\) seconds
 
 XCTMain([testCase(ExpectationsTestCase.allTests)])
 
 // CHECK: Test Suite '.*\.xctest' failed at \d+-\d+-\d+ \d+:\d+:\d+\.\d+
-// CHECK: \t Executed 35 tests, with 16 failures \(2 unexpected\) in \d+\.\d+ \(\d+\.\d+\) seconds
+// CHECK: \t Executed 38 tests, with 16 failures \(2 unexpected\) in \d+\.\d+ \(\d+\.\d+\) seconds
 // CHECK: Test Suite 'All tests' failed at \d+-\d+-\d+ \d+:\d+:\d+\.\d+
-// CHECK: \t Executed 35 tests, with 16 failures \(2 unexpected\) in \d+\.\d+ \(\d+\.\d+\) seconds
+// CHECK: \t Executed 38 tests, with 16 failures \(2 unexpected\) in \d+\.\d+ \(\d+\.\d+\) seconds