Runtime Warning Finesse (#1023)

Author: stephencelis

Sources/ComposableArchitecture/Debugging/ReducerInstrumentation.swift

@@ -110,7 +110,8 @@ func debugCaseOutput(_ value: Any) -> String {
     }
   }
 
-  return "\(type(of: value))\(debugCaseOutputHelp(value))"
+  return (value as? CustomDebugStringConvertible)?.debugDescription
+    ?? "\(type(of: value))\(debugCaseOutputHelp(value))"
 }
 
 private func isUnlabeledArgument(_ label: String) -> Bool {

Sources/ComposableArchitecture/Internal/Deprecations.swift

@@ -3,10 +3,6 @@ import Combine
 import SwiftUI
 import XCTestDynamicOverlay
 
-#if DEBUG
-  import os
-#endif
-
 // NB: Deprecated after 0.31.0:
 
 extension Reducer {
@@ -548,8 +544,7 @@ extension Reducer {
       }
       if index >= globalState[keyPath: toLocalState].endIndex {
         #if DEBUG
-          os_log(
-            .fault, dso: rw.dso, log: rw.log,
+          runtimeWarning(
             """
             A "forEach" reducer at "%@:%d" received an action when state contained no element at \
             that index. …
@@ -563,21 +558,21 @@ extension Reducer {
             reasons:
 
             • This "forEach" reducer was combined with or run from another reducer that removed \
-            the element at this index when it handled this action. To fix this make sure that \
-            this "forEach" reducer is run before any other reducers that can move or remove \
-            elements from state. This ensures that "forEach" reducers can handle their actions \
-            for the element at the intended index.
+            the element at this index when it handled this action. To fix this make sure that this \
+            "forEach" reducer is run before any other reducers that can move or remove elements \
+            from state. This ensures that "forEach" reducers can handle their actions for the \
+            element at the intended index.
 
             • An in-flight effect emitted this action while state contained no element at this \
             index. While it may be perfectly reasonable to ignore this action, you may want to \
             cancel the associated effect when moving or removing an element. If your "forEach" \
-            reducer returns any long-living effects, you should use the identifier-based \
-            "forEach" instead.
+            reducer returns any long-living effects, you should use the identifier-based "forEach" \
+            instead.
 
-            • This action was sent to the store while its state contained no element at this \
-            index. To fix this make sure that actions for this reducer can only be sent to a \
-            view store when its state contains an element at this index. In SwiftUI \
-            applications, use "ForEachStore".
+            • This action was sent to the store while its state contained no element at this index \
+            To fix this make sure that actions for this reducer can only be sent to a view store \
+            when its state contains an element at this index. In SwiftUI applications, use \
+            "ForEachStore".
             """,
             "\(file)",
             line,

Sources/ComposableArchitecture/Internal/RuntimeWarnings.swift

@@ -1,12 +1,13 @@
 #if DEBUG
   import os
+  import XCTestDynamicOverlay
 
   // NB: Xcode runtime warnings offer a much better experience than traditional assertions and
   //     breakpoints, but Apple provides no means of creating custom runtime warnings ourselves.
   //     To work around this, we hook into SwiftUI's runtime issue delivery mechanism, instead.
   //
   // Feedback filed: https://gist.github.com/stephencelis/a8d06383ed6ccde3e5ef5d1b3ad52bbc
-  let rw = (
+  private let rw = (
     dso: { () -> UnsafeMutableRawPointer in
       let count = _dyld_image_count()
       for i in 0..<count {
@@ -23,4 +24,15 @@
     }(),
     log: OSLog(subsystem: "com.apple.runtime-issues", category: "ComposableArchitecture")
   )
+
+  func runtimeWarning(
+    _ message: StaticString,
+    _ args: CVarArg...
+  ) {
+    unsafeBitCast(
+      os_log as (OSLogType, UnsafeRawPointer, OSLog, StaticString, CVarArg...) -> Void,
+      to: ((OSLogType, UnsafeRawPointer, OSLog, StaticString, [CVarArg]) -> Void).self
+    )(.fault, rw.dso, rw.log, message, args)
+    XCTFail(String(format: "\(message)", arguments: args))
+  }
 #endif

Sources/ComposableArchitecture/Reducer.swift

@@ -1,10 +1,6 @@
 import CasePaths
 import Combine
 
-#if DEBUG
-  import os
-#endif
-
 /// A reducer describes how to evolve the current state of an application to the next state, given
 /// an action, and describes what ``Effect``s should be executed later by the store, if any.
 ///
@@ -468,8 +464,7 @@ public struct Reducer<State, Action, Environment> {
 
       guard var localState = toLocalState.extract(from: globalState) else {
         #if DEBUG
-          os_log(
-            .fault, dso: rw.dso, log: rw.log,
+          runtimeWarning(
             """
             A reducer pulled back from "%@:%d" received an action when local state was \
             unavailable. …
@@ -678,8 +673,7 @@ public struct Reducer<State, Action, Environment> {
     .init { state, action, environment in
       guard state != nil else {
         #if DEBUG
-          os_log(
-            .fault, dso: rw.dso, log: rw.log,
+          runtimeWarning(
             """
             An "optional" reducer at "%@:%d" received an action when state was "nil". …
 
@@ -689,8 +683,8 @@ public struct Reducer<State, Action, Environment> {
             This is generally considered an application logic error, and can happen for a few \
             reasons:
 
-            • The optional reducer was combined with or run from another reducer that set \
-            "%@" to "nil" before the optional reducer ran. Combine or run optional reducers before \
+            • The optional reducer was combined with or run from another reducer that set "%@" to \
+            "nil" before the optional reducer ran. Combine or run optional reducers before \
             reducers that can set their state to "nil". This ensures that optional reducers can \
             handle their actions while their state is still non-"nil".
 
@@ -762,8 +756,7 @@ public struct Reducer<State, Action, Environment> {
       guard let (id, localAction) = toLocalAction.extract(from: globalAction) else { return .none }
       if globalState[keyPath: toLocalState][id: id] == nil {
         #if DEBUG
-          os_log(
-            .fault, dso: rw.dso, log: rw.log,
+          runtimeWarning(
             """
             A "forEach" reducer at "%@:%d" received an action when state contained no element with \
             that id. …
@@ -837,8 +830,7 @@ public struct Reducer<State, Action, Environment> {
 
       if globalState[keyPath: toLocalState][key] == nil {
         #if DEBUG
-          os_log(
-            .fault, dso: rw.dso, log: rw.log,
+          runtimeWarning(
             """
             A "forEach" reducer at "%@:%d" received an action when state contained no value at \
             that key. …

Sources/ComposableArchitecture/Store.swift

@@ -1,10 +1,6 @@
 import Combine
 import Foundation
 
-#if DEBUG
-  import os
-#endif
-
 /// A store represents the runtime that powers the application. It is the object that you will pass
 /// around to views that need to interact with the application.
 ///
@@ -420,8 +416,7 @@ public final class Store<State, Action> {
 
       switch status {
       case let .effectCompletion(action):
-        os_log(
-          .fault, dso: rw.dso, log: rw.log,
+        runtimeWarning(
           """
           An effect completed on a non-main thread. …
 
@@ -440,8 +435,7 @@ public final class Store<State, Action> {
         )
 
       case .`init`:
-        os_log(
-          .fault, dso: rw.dso, log: rw.log,
+        runtimeWarning(
           """
           A store initialized on a non-main thread. …
 
@@ -455,8 +449,7 @@ public final class Store<State, Action> {
         )
 
       case .scope:
-        os_log(
-          .fault, dso: rw.dso, log: rw.log,
+        runtimeWarning(
           """
           "Store.scope" was called on a non-main thread. …
 
@@ -470,8 +463,7 @@ public final class Store<State, Action> {
         )
 
       case let .send(action, originatingAction: nil):
-        os_log(
-          .fault, dso: rw.dso, log: rw.log,
+        runtimeWarning(
           """
           "ViewStore.send" was called on a non-main thread with: %@ …
 
@@ -486,8 +478,7 @@ public final class Store<State, Action> {
         )
 
       case let .send(action, originatingAction: .some(originatingAction)):
-        os_log(
-          .fault, dso: rw.dso, log: rw.log,
+        runtimeWarning(
           """
           An effect published an action on a non-main thread. …
 

Sources/ComposableArchitecture/SwiftUI/SwitchStore.swift

@@ -1,9 +1,5 @@
 import SwiftUI
 
-#if DEBUG
-  import os
-#endif
-
 /// A view that can switch over a store of enum state and handle each case.
 ///
 /// An application may model parts of its state with enums. For example, app state may differ if a
@@ -1201,8 +1197,7 @@ public struct _ExhaustivityCheckView<State, Action>: View {
       .background(Color.red.edgesIgnoringSafeArea(.all))
       .onAppear {
         #if DEBUG
-          os_log(
-            .fault, dso: rw.dso, log: rw.log,
+          runtimeWarning(
             """
             SwitchStore@%@:%d does not handle the current case. …
 

Sources/ComposableArchitecture/TestSupport/TestStore.swift

@@ -288,7 +288,7 @@
       }
     }
 
-    private struct TestAction {
+    private struct TestAction: CustomDebugStringConvertible {
       let origin: Origin
       let file: StaticString
       let line: UInt
@@ -297,6 +297,16 @@
         case send(LocalAction)
         case receive(Action)
       }
+
+      var debugDescription: String {
+        switch self.origin {
+        case let .send(action):
+          return debugCaseOutput(action)
+
+        case let .receive(action):
+          return debugCaseOutput(action)
+        }
+      }
     }
   }