From fc3bc4de9ad7d9bf6b9f8f6ad283c696eec2a661 Mon Sep 17 00:00:00 2001
From: Tristan Celder <tristan.celder@gmail.com>
Date: Fri, 8 May 2020 15:39:37 +0100
Subject: [PATCH] Removed ReplaySubject Subscriber accounting
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

The behaviour of Apple's stock Subjects suggests that Subscriber accounting (to prevent duplicate subscriptions of the same Subscriber) is the responsibility of the Subscriber itself – not the Subjects they're subscribed to.

Thanks for the heads-up @jasdev!
---
 Sources/Entwine/Operators/ReplaySubject.swift | 27 +++----------------
 Tests/EntwineTests/ReplaySubjectTests.swift   |  1 -
 2 files changed, 3 insertions(+), 25 deletions(-)

diff --git a/Sources/Entwine/Operators/ReplaySubject.swift b/Sources/Entwine/Operators/ReplaySubject.swift
index fb90c9d..9cda932 100644
--- a/Sources/Entwine/Operators/ReplaySubject.swift
+++ b/Sources/Entwine/Operators/ReplaySubject.swift
@@ -35,8 +35,6 @@ public final class ReplaySubject<Output, Failure: Error> {
     typealias Sink = AnySubscriber<Output, Failure>
     
     private var subscriptions = [ReplaySubjectSubscription<Sink>]()
-    private var subscriberIdentifiers = Set<CombineIdentifier>()
-    
     private var replayValues: ReplaySubjectValueBuffer<Output>
     private var completion: Subscribers.Completion<Failure>?
     
@@ -55,32 +53,13 @@ public final class ReplaySubject<Output, Failure: Error> {
 extension ReplaySubject: Publisher {
     
     public func receive<S : Subscriber>(subscriber: S) where Failure == S.Failure, Output == S.Input {
-        
-        guard !subscriberIdentifiers.contains(subscriber.combineIdentifier) else {
-            subscriber.receive(subscription: Subscriptions.empty)
-            return
-        }
-        
         let subscriberIdentifier = subscriber.combineIdentifier
-        
         let subscription = ReplaySubjectSubscription(sink: AnySubscriber(subscriber))
-        
-        // we use seperate collections for identifiers and subscriptions
-        // to improve performance of identifier lookups and to keep the
-        // order in which subscribers are signalled to be in the order that
-        // they intially subscribed.
-        
-        subscriberIdentifiers.insert(subscriberIdentifier)
         subscriptions.append(subscription)
-        
         subscription.cleanupHandler = { [weak self] in
-            
-            guard let self = self else { return }
-            
-            if let index = self.subscriptions.firstIndex(where: { subscriberIdentifier == $0.subscriberIdentifier }) {
-                self.subscriberIdentifiers.remove(subscriberIdentifier)
-                self.subscriptions.remove(at: index)
-            }
+            let firstIndex = self?.subscriptions.firstIndex { subscriberIdentifier == $0.subscriberIdentifier }
+            guard let index = firstIndex else { return }
+            self?.subscriptions.remove(at: index)
         }
         subscriber.receive(subscription: subscription)
         subscription.replayInputs(replayValues.buffer, completion: completion)
diff --git a/Tests/EntwineTests/ReplaySubjectTests.swift b/Tests/EntwineTests/ReplaySubjectTests.swift
index 33b44dc..c0eb598 100644
--- a/Tests/EntwineTests/ReplaySubjectTests.swift
+++ b/Tests/EntwineTests/ReplaySubjectTests.swift
@@ -169,7 +169,6 @@ final class ReplaySubjectTests: XCTestCase {
         scheduler.schedule(after: 600) { subject.send(0) }
         scheduler.schedule(after: 700) { subject.send(completion: .finished) }
 
-
         scheduler.resume()
         
         let expected1: TestSequence<Int, Never> = [