From 640f53a9b563fed949695e1639b0934e8d3ba2e4 Mon Sep 17 00:00:00 2001
From: Ian Keen <iankeen82@gmail.com>
Date: Mon, 6 Sep 2021 16:42:31 -0700
Subject: [PATCH 1/2] Add threading warning to Store.send

Any async Effect (including fireAndForget) could result in a runtime crash when updating internal state like `effectCancellables`
This adds a debug warning to let users know
---
 Sources/ComposableArchitecture/Store.swift | 33 ++++++++++++++++++++++
 1 file changed, 33 insertions(+)

diff --git a/Sources/ComposableArchitecture/Store.swift b/Sources/ComposableArchitecture/Store.swift
index d5cb4faf6f66..d8367fa98867 100644
--- a/Sources/ComposableArchitecture/Store.swift
+++ b/Sources/ComposableArchitecture/Store.swift
@@ -382,8 +382,41 @@ public final class Store<State, Action> {
 
       var didComplete = false
       let uuid = UUID()
+
+      #if DEBUG
+      let initalThread = Thread.current
+      initalThread.threadDictionary[uuid] = true
+      #endif
+
       let effectCancellable = effect.sink(
         receiveCompletion: { [weak self] _ in
+          //
+          #if DEBUG
+          if Thread.current.threadDictionary[uuid] == nil {
+            breakpoint(
+            """
+            ---
+            Warning: Store.send
+
+            The Store class is not thread-safe, and so all interactions with an instance of Store
+            (including all of its scopes and derived ViewStores) must be done on the same thread.
+
+            \(debugCaseOutput(action)) has produced an Effect that was completed on a different thread \
+            from the one it was executed on.
+              
+            Starting thread: \(initalThread)
+            Final thread: \(Thread.current)
+              
+            Possible fixes for this are:
+
+            * Add a .receive(on:) to the Effect to ensure it completes on this Stores correct thread.
+            """
+            )
+          }
+
+          Thread.current.threadDictionary[uuid] = nil
+          #endif
+
           didComplete = true
           self?.effectCancellables[uuid] = nil
         },

From ee34b8fb45155ce1a0bb9c1cf581a4d453d7eb41 Mon Sep 17 00:00:00 2001
From: Ian Keen <iankeen82@gmail.com>
Date: Mon, 6 Sep 2021 16:44:39 -0700
Subject: [PATCH 2/2] Remove comment

---
 Sources/ComposableArchitecture/Store.swift | 1 -
 1 file changed, 1 deletion(-)

diff --git a/Sources/ComposableArchitecture/Store.swift b/Sources/ComposableArchitecture/Store.swift
index d8367fa98867..86b0c4b862cd 100644
--- a/Sources/ComposableArchitecture/Store.swift
+++ b/Sources/ComposableArchitecture/Store.swift
@@ -390,7 +390,6 @@ public final class Store<State, Action> {
 
       let effectCancellable = effect.sink(
         receiveCompletion: { [weak self] _ in
-          //
           #if DEBUG
           if Thread.current.threadDictionary[uuid] == nil {
             breakpoint(