Deadlock workaround (#219)

* Add test for deadlock.

* wip

* wip

* run more tests on linux

Author: mbrandonw

Sources/Dependencies/DependencyValues.swift

@@ -13,11 +13,11 @@ import XCTestDynamicOverlay
 
 #if _runtime(_ObjC)
   extension DispatchQueue {
-    fileprivate static func mainSync<R>(execute block: @Sendable () -> R) -> R {
+    fileprivate static func mainASAP(execute block: @escaping @Sendable () -> Void) {
       if Thread.isMainThread {
         return block()
       } else {
-        return Self.main.sync(execute: block)
+        return Self.main.async(execute: block)
       }
     }
   }
@@ -129,7 +129,7 @@ public struct DependencyValues: Sendable {
   /// that the library manages for you when you use the ``Dependency`` property wrapper.
   public init() {
     #if _runtime(_ObjC)
-      DispatchQueue.mainSync {
+      DispatchQueue.mainASAP {
         guard
           let XCTestObservation = objc_getProtocol("XCTestObservation"),
           let XCTestObservationCenter = NSClassFromString("XCTestObservationCenter"),

Tests/DependenciesTests/DependencyValuesTests.swift

@@ -398,32 +398,30 @@ final class DependencyValuesTests: XCTestCase {
       self.wait(for: [expectation], timeout: 1)
     }
 
-    #if !os(Linux)
-      @MainActor
-      func testEscapingInFeatureModel_InstanceVariablePropagated() {
-        let expectation = self.expectation(description: "escape")
+    @MainActor
+    func testEscapingInFeatureModel_InstanceVariablePropagated() async {
+      let expectation = self.expectation(description: "escape")
 
-        @MainActor
-        class FeatureModel /*: ObservableObject*/ {
-          @Dependency(\.fullDependency) var fullDependency
-          func doSomething(expectation: XCTestExpectation) {
-            DispatchQueue.main.async {
-              XCTAssertEqual(self.fullDependency.value, 42)
-              expectation.fulfill()
-            }
+      @MainActor
+      class FeatureModel /*: ObservableObject*/ {
+        @Dependency(\.fullDependency) var fullDependency
+        func doSomething(expectation: XCTestExpectation) {
+          DispatchQueue.main.async {
+            XCTAssertEqual(self.fullDependency.value, 42)
+            expectation.fulfill()
           }
         }
+      }
 
-        let model = withDependencies {
-          $0.fullDependency.value = 42
-        } operation: {
-          FeatureModel()
-        }
-
-        model.doSomething(expectation: expectation)
-        self.wait(for: [expectation], timeout: 1)
+      let model = withDependencies {
+        $0.fullDependency.value = 42
+      } operation: {
+        FeatureModel()
       }
-    #endif
+
+      model.doSomething(expectation: expectation)
+      await fulfillment(of: [expectation], timeout: 1)
+    }
 
     func testEscapingInFeatureModel_NotPropagated() async {
       let expectation = self.expectation(description: "escape")
@@ -679,6 +677,21 @@ final class DependencyValuesTests: XCTestCase {
       }
     }
   }
+
+  @MainActor
+  func testDeadlock() async {
+    DispatchQueue(label: "queue", qos: .utility).async {
+      @Dependency(\.date) var date
+      _ = date
+    }
+
+    // Block main thread for 0.1 seconds.
+    let start = Date()
+    while Date().timeIntervalSince(start) < 0.1 {}
+
+    @Dependency(\.date) var date
+    _ = date
+  }
 }
 
 struct CountInitDependency: TestDependencyKey {

Tests/DependenciesTests/FireAndForgetTests.swift

@@ -1,12 +1,12 @@
 import Dependencies
 import XCTest
 
-@MainActor
 final class FireAndForgetTests: XCTestCase {
   @Dependency(\.fireAndForget) var fireAndForget
 
   // NB: These tests fail/crash in Wasm.
   #if !os(WASI)
+    @MainActor
     func testTestContext() async throws {
       let didExecute = ActorIsolated(false)
 
@@ -19,6 +19,7 @@ final class FireAndForgetTests: XCTestCase {
       XCTAssertEqual(value, true)
     }
 
+    @MainActor
     func testTestContext_Cancellation() async throws {
       let didExecute = ActorIsolated(false)
 
@@ -36,6 +37,7 @@ final class FireAndForgetTests: XCTestCase {
       XCTAssertEqual(value, true)
     }
 
+    @MainActor
     func testLiveContext() async throws {
       try await withDependencies {
         $0.context = .live
@@ -58,6 +60,7 @@ final class FireAndForgetTests: XCTestCase {
   #endif
 
   #if !os(Linux) && !os(WASI) && !os(Windows)
+    @MainActor
     func testLiveContext_DependencyAccess() async {
       await withDependencies {
         $0.context = .live