0.33.0

Examples/SyncUps/SyncUps/SyncUpForm.swift

@@ -1,6 +1,6 @@
 import SwiftUI
-import VDStore
 import VDFlow
+import VDStore
 
 struct SyncUpForm: Equatable {
 
@@ -60,7 +60,7 @@ struct SyncUpFormView: View {
 		Form {
 			Section {
 				TextField("Title", text: _state.syncUp.title)
-                    .focused(_state.focus, equals: .title)
+					.focused(_state.focus, equals: .title)
 				HStack {
 					Slider(value: _state.syncUp.duration.minutes, in: 5 ... 30, step: 1) {
 						Text("Length")
@@ -75,7 +75,7 @@ struct SyncUpFormView: View {
 			Section {
 				ForEach(_state.syncUp.attendees) { attendee in
 					TextField("Name", text: attendee.name)
-                        .focused(_state.focus, equals: .attendee(attendee.id))
+						.focused(_state.focus, equals: .attendee(attendee.id))
 				}
 				.onDelete { indices in
 					$state.deleteAttendees(atOffsets: indices)

README.md

@@ -164,7 +164,7 @@ import PackageDescription
 let package = Package(
   name: "SomeProject",
   dependencies: [
-    .package(url: "https://github.com/dankinsoid/VDStore.git", from: "0.32.0")
+    .package(url: "https://github.com/dankinsoid/VDStore.git", from: "0.33.0")
   ],
   targets: [
     .target(name: "SomeProject", dependencies: ["VDStore"])

Sources/VDStore/Store.swift

@@ -82,7 +82,7 @@ import SwiftUI
 ///
 /// ### Thread safety
 ///
-/// The `Store` class is isolated to main actor by @MainActor attribute.
+/// The `Store` class is isolated to main actor by @MainActor attribute, but the thread safety is not guaranteed. All the state changes should be done on the main thread.
 @propertyWrapper
 @dynamicMemberLookup
 @MainActor

Sources/VDStore/Utils/RuntimeWarnings.swift

@@ -0,0 +1,71 @@
+import Foundation
+
+@_transparent
+@usableFromInline
+@inline(__always)
+func runtimeWarn(
+	_ message: @autoclosure () -> String,
+	category: String? = "VDStore"
+) {
+	#if DEBUG
+	let message = message()
+	let category = category ?? "Runtime Warning"
+	if _XCTIsTesting {
+		#if canImport(XCTest)
+		XCTFail(message)
+		#endif
+	} else {
+		#if canImport(os)
+		os_log(
+			.fault,
+			dso: dso,
+			log: OSLog(subsystem: "com.apple.runtime-issues", category: category),
+			"%@",
+			message
+		)
+		#else
+		fputs("\(formatter.string(from: Date())) [\(category)] \(message)\n", stderr)
+		#endif
+	}
+	#endif
+}
+
+#if DEBUG
+#if canImport(XCTest)
+import XCTest
+#endif
+
+#if canImport(os)
+import os
+
+// NB: Xcode runtime warnings offer a much better experience than traditional assertions and
+//     breakpoints, but Apple provides no means of creating custom runtime warnings ourselves.
+//     To work around this, we hook into SwiftUI's runtime issue delivery mechanism, instead.
+//
+// Feedback filed: https://gist.github.com/stephencelis/a8d06383ed6ccde3e5ef5d1b3ad52bbc
+@usableFromInline
+let dso = { () -> UnsafeMutableRawPointer in
+	let count = _dyld_image_count()
+	for i in 0 ..< count {
+		if let name = _dyld_get_image_name(i) {
+			let swiftString = String(cString: name)
+			if swiftString.hasSuffix("/SwiftUI") {
+				if let header = _dyld_get_image_header(i) {
+					return UnsafeMutableRawPointer(mutating: UnsafeRawPointer(header))
+				}
+			}
+		}
+	}
+	return UnsafeMutableRawPointer(mutating: #dsohandle)
+}()
+#else
+import Foundation
+
+@usableFromInline
+let formatter: DateFormatter = {
+	let formatter = DateFormatter()
+	formatter.dateFormat = "yyyy-MM-dd HH:MM:SS.sssZ"
+	return formatter
+}()
+#endif
+#endif

Sources/VDStore/Utils/StoreBox.swift

@@ -65,6 +65,7 @@ private final class StoreRootBox<State>: StoreRootBoxType, Publisher {
 	private var _state: State
 	var state: State {
 		get {
+			checkStateThread()
 			_$observationRegistrar.access(box: self)
 			return _state
 		}
@@ -206,3 +207,15 @@ private struct MockObservationRegistrar: ObservationRegistrarProtocol {
 		try mutation()
 	}
 }
+
+private func checkStateThread() {
+	threadCheck(message:
+		"""
+		Store state was accessed on a non-main thread. …
+
+		The "Store" struct is not thread-safe, and so all interactions with an instance of \
+		"Store" (including all of its scopes and derived view stores) must be done on the main \
+		thread.
+		"""
+	)
+}

Sources/VDStore/Utils/ThreadCheck.swift

@@ -0,0 +1,12 @@
+import Foundation
+
+#if DEBUG
+@inline(__always)
+func threadCheck(message: @autoclosure () -> String) {
+	guard !Thread.isMainThread else { return }
+	runtimeWarn(message())
+}
+#else
+@_transparent
+func threadCheck(status: ThreadCheckStatus) {}
+#endif

Sources/VDStore/ViewStore.swift

@@ -20,11 +20,11 @@ public struct ViewStore<State>: DynamicProperty {
 		nonmutating set { store.state = newValue }
 	}
 
-    public var projectedValue: Store<State> {
-        store
-    }
+	public var projectedValue: Store<State> {
+		store
+	}
 
-    public var store: Store<State> {
+	public var store: Store<State> {
 		let result: Store<State>
 		switch property {
 		case let .stateObject(observable):
@@ -61,11 +61,11 @@ public struct ViewStore<State>: DynamicProperty {
 		self.init(Store(wrappedValue: state))
 	}
 
-    public subscript<LocalValue>(
-        dynamicMember keyPath: WritableKeyPath<State, LocalValue>
-    ) -> Binding<LocalValue> {
-        store.binding[dynamicMember: keyPath]
-    }
+	public subscript<LocalValue>(
+		dynamicMember keyPath: WritableKeyPath<State, LocalValue>
+	) -> Binding<LocalValue> {
+		store.binding[dynamicMember: keyPath]
+	}
 
 	@MainActor
 	private enum Property: DynamicProperty {