PackageToJS: Fail tests when continuation leaks are detected

Plugins/PackageToJS/Fixtures/ContinuationLeakInTest/SwiftTesting/Package.swift

@@ -0,0 +1,17 @@
+// swift-tools-version: 6.0
+import PackageDescription
+
+let package = Package(
+    name: "Check",
+    dependencies: [.package(name: "JavaScriptKit", path: "../../../../../")],
+    targets: [
+        .testTarget(
+            name: "CheckTests",
+            dependencies: [
+                "JavaScriptKit",
+                .product(name: "JavaScriptEventLoopTestSupport", package: "JavaScriptKit"),
+            ],
+            path: "Tests"
+        )
+    ]
+)

Plugins/PackageToJS/Fixtures/ContinuationLeakInTest/SwiftTesting/Tests/CheckTests.swift

@@ -0,0 +1,5 @@
+import Testing
+
+@Test func never() async throws {
+    let _: Void = await withUnsafeContinuation { _ in }
+}

Plugins/PackageToJS/Fixtures/ContinuationLeakInTest/XCTest/Package.swift

@@ -0,0 +1,17 @@
+// swift-tools-version: 6.0
+import PackageDescription
+
+let package = Package(
+    name: "Check",
+    dependencies: [.package(name: "JavaScriptKit", path: "../../../../../")],
+    targets: [
+        .testTarget(
+            name: "CheckTests",
+            dependencies: [
+                "JavaScriptKit",
+                .product(name: "JavaScriptEventLoopTestSupport", package: "JavaScriptKit"),
+            ],
+            path: "Tests"
+        )
+    ]
+)

Plugins/PackageToJS/Fixtures/ContinuationLeakInTest/XCTest/Tests/CheckTests.swift

@@ -0,0 +1,7 @@
+import XCTest
+
+final class CheckTests: XCTestCase {
+    func testNever() async throws {
+        let _: Void = await withUnsafeContinuation { _ in }
+    }
+}

Plugins/PackageToJS/Templates/bin/test.js

@@ -68,6 +68,19 @@ const harnesses = {
                     options = prelude.setupOptions(options, { isMainThread: true })
                 }
             }
+            process.on("beforeExit", () => {
+                // NOTE: "beforeExit" is fired when the process exits gracefully without calling `process.exit`
+                // Either XCTest or swift-testing should always call `process.exit` through `proc_exit` even
+                // if the test succeeds. So exiting gracefully means something went wrong (e.g. withUnsafeContinuation is leaked)
+                // Therefore, we exit with code 1 to indicate that the test execution failed.
+                console.error(`
+
+=================================================================================================
+Detected that the test execution ended without a termination signal from the testing framework.
+Hint: This typically means that a continuation leak occurred.
+=================================================================================================`)
+                process.exit(1)
+            })
             await instantiate(options)
         } catch (e) {
             if (e instanceof WebAssembly.CompileError) {

Plugins/PackageToJS/Tests/ExampleTests.swift

@@ -88,7 +88,6 @@ extension Trait where Self == ConditionTrait {
                     atPath: destinationPath.path,
                     withDestinationPath: linkDestination
                 )
-                enumerator.skipDescendants()
                 continue
             }
 
@@ -117,8 +116,11 @@ extension Trait where Self == ConditionTrait {
     typealias RunProcess = (_ executableURL: URL, _ args: [String], _ env: [String: String]) throws -> Void
     typealias RunSwift = (_ args: [String], _ env: [String: String]) throws -> Void
 
-    func withPackage(at path: String, body: (URL, _ runProcess: RunProcess, _ runSwift: RunSwift) throws -> Void) throws
-    {
+    func withPackage(
+        at path: String,
+        assertTerminationStatus: (Int32) -> Bool = { $0 == 0 },
+        body: @escaping (URL, _ runProcess: RunProcess, _ runSwift: RunSwift) throws -> Void
+    ) throws {
         try withTemporaryDirectory { tempDir, retain in
             let destination = tempDir.appending(path: Self.repoPath.lastPathComponent)
             try Self.copyRepository(to: destination)
@@ -139,11 +141,11 @@ extension Trait where Self == ConditionTrait {
 
                 try process.run()
                 process.waitUntilExit()
-                if process.terminationStatus != 0 {
+                if !assertTerminationStatus(process.terminationStatus) {
                     retain = true
                 }
                 try #require(
-                    process.terminationStatus == 0,
+                    assertTerminationStatus(process.terminationStatus),
                     """
                     Swift package should build successfully, check \(destination.appending(path: path).path) for details
                     stdout: \(stdoutPath.path)
@@ -275,4 +277,29 @@ extension Trait where Self == ConditionTrait {
             )
         }
     }
+
+    @Test(.requireSwiftSDK)
+    func continuationLeakInTest_XCTest() throws {
+        let swiftSDKID = try #require(Self.getSwiftSDKID())
+        try withPackage(
+            at: "Plugins/PackageToJS/Fixtures/ContinuationLeakInTest/XCTest",
+            assertTerminationStatus: { $0 != 0 }
+        ) { packageDir, _, runSwift in
+            try runSwift(["package", "--disable-sandbox", "--swift-sdk", swiftSDKID, "js", "test"], [:])
+        }
+    }
+
+    #if compiler(>=6.1)
+    // TODO: Remove triple restriction once swift-testing is shipped in p1-threads SDK
+    @Test(.requireSwiftSDK(triple: "wasm32-unknown-wasi"))
+    func continuationLeakInTest_SwiftTesting() throws {
+        let swiftSDKID = try #require(Self.getSwiftSDKID())
+        try withPackage(
+            at: "Plugins/PackageToJS/Fixtures/ContinuationLeakInTest/SwiftTesting",
+            assertTerminationStatus: { $0 != 0 }
+        ) { packageDir, _, runSwift in
+            try runSwift(["package", "--disable-sandbox", "--swift-sdk", swiftSDKID, "js", "test"], [:])
+        }
+    }
+    #endif
 }