Use source location for subscriber name

Author: ra1028

Sources/Atoms/Context/AtomTestContext.swift

@@ -12,8 +12,9 @@ public struct AtomTestContext: AtomWatchableContext {
     private let state: State
 
     /// Creates a new test context instance with fresh internal state.
-    public init() {
-        state = State()
+    public init(fileID: String = #fileID, line: UInt = #line) {
+        let location = SourceLocation(fileID: fileID, line: line)
+        state = State(location: location)
     }
 
     /// A callback to perform when any of atoms watched by this context is updated.
@@ -264,16 +265,21 @@ private extension AtomTestContext {
         private let _store = Store()
         private let _container = SubscriptionContainer()
 
-        var overrides = Overrides()
+        let location: SourceLocation
         let notifier = PassthroughSubject<Void, Never>()
+        var overrides = Overrides()
         var onUpdate: (() -> Void)?
 
+        init(location: SourceLocation) {
+            self.location = location
+        }
+
         var store: StoreContext {
             StoreContext(_store, overrides: overrides)
         }
 
         var container: SubscriptionContainer.Wrapper {
-            _container.wrapper
+            _container.wrapper(location: location)
         }
 
         func notifyUpdate() {

Sources/Atoms/Core/AtomTypeKey.swift

@@ -7,15 +7,15 @@ internal struct AtomTypeKey: Hashable, CustomStringConvertible {
         getName = { String(describing: Node.self) }
     }
 
-    static func == (lhs: Self, rhs: Self) -> Bool {
-        lhs.identifier == rhs.identifier
-    }
-
     var description: String {
         getName()
     }
 
     func hash(into hasher: inout Hasher) {
         hasher.combine(identifier)
     }
+
+    static func == (lhs: Self, rhs: Self) -> Bool {
+        lhs.identifier == rhs.identifier
+    }
 }

Sources/Atoms/Core/SourceLocation.swift

@@ -0,0 +1,4 @@
+internal struct SourceLocation: Equatable {
+    let fileID: String
+    let line: UInt
+}

Sources/Atoms/Core/SubscriptionContainer.swift

@@ -3,17 +3,17 @@
 internal final class SubscriptionContainer {
     private var subscriptions = [AtomKey: Subscription]()
 
-    var wrapper: Wrapper {
-        Wrapper(self)
-    }
-
     nonisolated init() {}
 
     deinit {
         for subscription in ContiguousArray(subscriptions.values) {
             subscription.unsubscribe()
         }
     }
+
+    func wrapper(location: SourceLocation) -> Wrapper {
+        Wrapper(self, location: location)
+    }
 }
 
 internal extension SubscriptionContainer {
@@ -29,9 +29,9 @@ internal extension SubscriptionContainer {
             nonmutating set { container?.subscriptions = newValue }
         }
 
-        init(_ container: SubscriptionContainer) {
+        init(_ container: SubscriptionContainer, location: SourceLocation) {
             self.container = container
-            self.key = SubscriptionKey(container)
+            self.key = SubscriptionKey(container, location: location)
         }
     }
 }

Sources/Atoms/Core/SubscriptionKey.swift

@@ -1,11 +1,22 @@
 internal struct SubscriptionKey: Hashable, CustomStringConvertible {
     private let identifier: ObjectIdentifier
+    private let location: SourceLocation
 
-    init(_ container: SubscriptionContainer) {
-        identifier = ObjectIdentifier(container)
+    init(_ container: SubscriptionContainer, location: SourceLocation) {
+        self.identifier = ObjectIdentifier(container)
+        self.location = location
     }
 
     var description: String {
-        "Subscriber(\(hashValue))"
+        "\(location.fileID):\(location.line)"
+    }
+
+    // Ignores `location` because it is a debugging metadata.
+    func hash(into hasher: inout Hasher) {
+        hasher.combine(identifier)
+    }
+
+    static func == (lhs: Self, rhs: Self) -> Bool {
+        lhs.identifier == rhs.identifier
     }
 }

Sources/Atoms/PropertyWrapper/ViewContext.swift

@@ -39,9 +39,12 @@ public struct ViewContext: DynamicProperty {
     @Environment(\.store)
     private var _store
 
+    private let location: SourceLocation
+
     /// Creates a view context.
-    public init() {
+    public init(fileID: String = #fileID, line: UInt = #line) {
         _state = StateObject(wrappedValue: State())
+        location = SourceLocation(fileID: fileID, line: line)
     }
 
     /// The underlying view context to interact with atoms.
@@ -52,7 +55,7 @@ public struct ViewContext: DynamicProperty {
     public var wrappedValue: AtomViewContext {
         AtomViewContext(
             store: _store,
-            container: state.container.wrapper,
+            container: state.container.wrapper(location: location),
             notifyUpdate: state.objectWillChange.send
         )
     }

Sources/Atoms/PropertyWrapper/Watch.swift

@@ -29,8 +29,9 @@ public struct Watch<Node: Atom>: DynamicProperty {
     private var context
 
     /// Creates a watch with the atom that to be watched.
-    public init(_ atom: Node) {
+    public init(_ atom: Node, fileID: String = #fileID, line: UInt = #line) {
         self.atom = atom
+        self._context = ViewContext(fileID: fileID, line: line)
     }
 
     /// The underlying value associated with the given atom.

Sources/Atoms/PropertyWrapper/WatchState.swift

@@ -38,8 +38,9 @@ public struct WatchState<Node: StateAtom>: DynamicProperty {
     private var context
 
     /// Creates a watch with the atom that to be watched.
-    public init(_ atom: Node) {
+    public init(_ atom: Node, fileID: String = #fileID, line: UInt = #line) {
         self.atom = atom
+        self._context = ViewContext(fileID: fileID, line: line)
     }
 
     /// The underlying value associated with the given atom.

Sources/Atoms/PropertyWrapper/WatchStateObject.swift

@@ -72,8 +72,9 @@ public struct WatchStateObject<Node: ObservableObjectAtom>: DynamicProperty {
     private var context
 
     /// Creates a watch with the atom that to be watched.
-    public init(_ atom: Node) {
+    public init(_ atom: Node, fileID: String = #fileID, line: UInt = #line) {
         self.atom = atom
+        self._context = ViewContext(fileID: fileID, line: line)
     }
 
     /// The underlying observable object associated with the given atom.

Sources/Atoms/Snapshot.swift

@@ -63,9 +63,10 @@ public struct Snapshot: CustomStringConvertible {
 
             if let subscribers = subscriptions[key]?.keys, !subscribers.isEmpty {
                 for subscriber in subscribers {
+                    let node = "\(subscriber.description.quoted) [style=filled]"
                     let edge = "\(key.description.quoted) -> \(subscriber.description.quoted)"
+                    statements.append(node)
                     statements.append(edge)
-                    statements.append("\(subscriber.description.quoted) [style=filled]")
                 }
             }
         }