Disable printing by default for DebugReducer when running SwiftUI Previews (#1625)

* Disable printing by default for `DebugReducer` when running SwiftUI Previews

* Update Sources/ComposableArchitecture/Internal/SwiftUIPreviews.swift

Co-authored-by: Stephen Celis <[email protected]>

* Use `@Dependency(\.context)`

Co-authored-by: Stephen Celis <[email protected]>
(cherry picked from commit 4ac937402d2597ec1ecb4faccdb710fc69b5795c)

Author: 2 people

Sources/ComposableArchitecture/Reducer/Reducers/DebugReducer.swift

@@ -31,6 +31,8 @@ public struct _ReducerPrinter<State, Action> {
 extension _ReducerPrinter {
   public static var customDump: Self {
     Self { receivedAction, oldState, newState in
+      @Dependency(\.context) var context
+      guard context != .preview else { return }
       var target = ""
       target.write("received action:\n")
       CustomDump.customDump(receivedAction, to: &target, indent: 2)
@@ -42,6 +44,8 @@ extension _ReducerPrinter {
 
   public static var actionLabels: Self {
     Self { receivedAction, _, _ in
+      @Dependency(\.context) var context
+      guard context != .preview else { return }
       print("received action: \(debugCaseOutput(receivedAction))")
     }
   }

Tests/ComposableArchitectureTests/DebugTests.swift

@@ -220,5 +220,20 @@
       let store = TestStore(initialState: 0, reducer: DebuggedReducer()._printChanges())
       await store.send(true) { $0 = 1 }
     }
+    
+    @MainActor
+    func testDebugReducerInPreview() async {
+      struct DebuggedReducer: ReducerProtocol {
+        typealias State = Int
+        typealias Action = Bool
+        func reduce(into state: inout Int, action: Bool) -> EffectTask<Bool> {
+          state += action ? 1 : -1
+          return .none
+        }
+      }
+      let store = TestStore(initialState: 0, reducer: DebuggedReducer()._printChanges())
+      store.dependencies.context = .preview
+      await store.send(true) { $0 = 1 }
+    }
   }
 #endif