From ce6b0e7faae73f9693313523daab867971c517d2 Mon Sep 17 00:00:00 2001
From: Kabir Oberai <oberai.kabir@gmail.com>
Date: Tue, 15 Oct 2024 20:13:29 -0400
Subject: [PATCH] Slow fix

---
 .../Internal/CurrentValueRelay.swift          | 63 +++++++++----------
 1 file changed, 29 insertions(+), 34 deletions(-)

diff --git a/Sources/ComposableArchitecture/Internal/CurrentValueRelay.swift b/Sources/ComposableArchitecture/Internal/CurrentValueRelay.swift
index 98e22980850c..fccd40e94336 100644
--- a/Sources/ComposableArchitecture/Internal/CurrentValueRelay.swift
+++ b/Sources/ComposableArchitecture/Internal/CurrentValueRelay.swift
@@ -5,7 +5,7 @@ final class CurrentValueRelay<Output>: Publisher {
   typealias Failure = Never
 
   private var currentValue: Output
-  private let lock: os_unfair_lock_t
+  private let lock: NSRecursiveLock
   private var subscriptions = ContiguousArray<Subscription>()
 
   var value: Output {
@@ -15,13 +15,7 @@ final class CurrentValueRelay<Output>: Publisher {
 
   init(_ value: Output) {
     self.currentValue = value
-    self.lock = os_unfair_lock_t.allocate(capacity: 1)
-    self.lock.initialize(to: os_unfair_lock())
-  }
-
-  deinit {
-    self.lock.deinitialize(count: 1)
-    self.lock.deallocate()
+    self.lock = NSRecursiveLock()
   }
 
   func receive(subscriber: some Subscriber<Output, Never>) {
@@ -36,7 +30,7 @@ final class CurrentValueRelay<Output>: Publisher {
     self.lock.sync {
       self.currentValue = value
     }
-    for subscription in self.lock.sync({ self.subscriptions }) {
+    for subscription in self.lock.sync(work: { self.subscriptions }) {
       subscription.receive(value)
     }
   }
@@ -52,27 +46,28 @@ final class CurrentValueRelay<Output>: Publisher {
 
 extension CurrentValueRelay {
   fileprivate final class Subscription: Combine.Subscription, Equatable {
-    private var demand = Subscribers.Demand.none
-    private var downstream: (any Subscriber<Output, Never>)?
-    private let lock: os_unfair_lock_t
+    private var _demand = Subscribers.Demand.none
+
+    private var _downstream: (any Subscriber<Output, Never>)?
+    var downstream: (any Subscriber<Output, Never>)? {
+      var downstream: (any Subscriber<Output, Never>)?
+      self.lock.sync { downstream = _downstream }
+      return downstream
+    }
+
+    private let lock: NSRecursiveLock
     private var receivedLastValue = false
     private var upstream: CurrentValueRelay?
 
     init(upstream: CurrentValueRelay, downstream: any Subscriber<Output, Never>) {
       self.upstream = upstream
-      self.downstream = downstream
-      self.lock = os_unfair_lock_t.allocate(capacity: 1)
-      self.lock.initialize(to: os_unfair_lock())
-    }
-
-    deinit {
-      self.lock.deinitialize(count: 1)
-      self.lock.deallocate()
+      self._downstream = downstream
+      self.lock = upstream.lock
     }
 
     func cancel() {
       self.lock.sync {
-        self.downstream = nil
+        self._downstream = nil
         self.upstream?.remove(self)
         self.upstream = nil
       }
@@ -81,24 +76,24 @@ extension CurrentValueRelay {
     func receive(_ value: Output) {
       guard let downstream else { return }
 
-      switch self.demand {
+      self.lock.lock()
+      switch self._demand {
       case .unlimited:
+        self.lock.unlock()
         // NB: Adding to unlimited demand has no effect and can be ignored.
         _ = downstream.receive(value)
 
       case .none:
-        self.lock.sync {
-          self.receivedLastValue = false
-        }
+        self.receivedLastValue = false
+        self.lock.unlock()
 
       default:
-        self.lock.sync {
-          self.receivedLastValue = true
-          self.demand -= 1
-        }
+        self.receivedLastValue = true
+        self._demand -= 1
+        self.lock.unlock()
         let moreDemand = downstream.receive(value)
         self.lock.sync {
-          self.demand += moreDemand
+          self._demand += moreDemand
         }
       }
     }
@@ -109,7 +104,7 @@ extension CurrentValueRelay {
       guard let downstream else { return }
 
       self.lock.lock()
-      self.demand += demand
+      self._demand += demand
 
       guard
         !self.receivedLastValue,
@@ -121,18 +116,18 @@ extension CurrentValueRelay {
 
       self.receivedLastValue = true
 
-      switch self.demand {
+      switch self._demand {
       case .unlimited:
         self.lock.unlock()
         // NB: Adding to unlimited demand has no effect and can be ignored.
         _ = downstream.receive(value)
 
       default:
-        self.demand -= 1
+        self._demand -= 1
         self.lock.unlock()
         let moreDemand = downstream.receive(value)
         self.lock.lock()
-        self.demand += moreDemand
+        self._demand += moreDemand
         self.lock.unlock()
       }
     }