Specify action formatting when using .debug (pointfreeco#187)

* Customize action formatting when debugging reducers.

* wip

* wip

* include type

* wip

* tests

* docs

* fix tests

Co-authored-by: Stephen Celis <stephen@stephencelis.com>

Examples/Todos/Todos/Todos.swift

@@ -131,7 +131,8 @@ let appReducer = Reducer<AppState, AppAction, AppEnvironment>.combine(
     environment: { _ in TodoEnvironment() }
   )
 )
-.debug()
+
+.debugActions(actionFormat: .labelsOnly)
 
 struct AppView: View {
   struct ViewState: Equatable {

Sources/ComposableArchitecture/Debugging/ReducerDebugging.swift

@@ -1,6 +1,27 @@
 import CasePaths
 import Dispatch
 
+/// Determines how the string description of an action should be printed when using the `.debug()`
+/// higher-order reducer.
+public enum ActionFormat {
+  /// Prints the action in a single line by only specifying the labels of the associated values:
+  ///
+  ///     Action.screenA(.row(index:, action: .textChanged(query:)))
+  case labelsOnly
+  /// Prints the action in a multiline, pretty-printed format, including all the labels of
+  /// any associated values, as well as the data held in the associated values:
+  ///
+  ///     Action.screenA(
+  ///       ScreenA.row(
+  ///         index: 1,
+  ///         action: RowAction.textChanged(
+  ///           query: "Hi"
+  ///         )
+  ///       )
+  ///     )
+  case prettyPrint
+}
+
 extension Reducer {
   /// Prints debug messages describing all received actions and state mutations.
   ///
@@ -15,11 +36,18 @@ extension Reducer {
   /// - Returns: A reducer that prints debug messages for all received actions.
   public func debug(
     _ prefix: String = "",
+    actionFormat: ActionFormat = .prettyPrint,
     environment toDebugEnvironment: @escaping (Environment) -> DebugEnvironment = { _ in
       DebugEnvironment()
     }
   ) -> Reducer {
-    self.debug(prefix, state: { $0 }, action: .self, environment: toDebugEnvironment)
+    self.debug(
+      prefix,
+      state: { $0 },
+      action: .self,
+      actionFormat: actionFormat,
+      environment: toDebugEnvironment
+    )
   }
 
   /// Prints debug messages describing all received actions.
@@ -35,11 +63,18 @@ extension Reducer {
   /// - Returns: A reducer that prints debug messages for all received actions.
   public func debugActions(
     _ prefix: String = "",
+    actionFormat: ActionFormat = .prettyPrint,
     environment toDebugEnvironment: @escaping (Environment) -> DebugEnvironment = { _ in
       DebugEnvironment()
     }
   ) -> Reducer {
-    self.debug(prefix, state: { _ in () }, action: .self, environment: toDebugEnvironment)
+    self.debug(
+      prefix,
+      state: { _ in () },
+      action: .self,
+      actionFormat: actionFormat,
+      environment: toDebugEnvironment
+    )
   }
 
   /// Prints debug messages describing all received local actions and local state mutations.
@@ -59,6 +94,7 @@ extension Reducer {
     _ prefix: String = "",
     state toLocalState: @escaping (State) -> LocalState,
     action toLocalAction: CasePath<Action, LocalAction>,
+    actionFormat: ActionFormat = .prettyPrint,
     environment toDebugEnvironment: @escaping (Environment) -> DebugEnvironment = { _ in
       DebugEnvironment()
     }
@@ -73,9 +109,12 @@ extension Reducer {
         return .concatenate(
           .fireAndForget {
             debugEnvironment.queue.async {
-              let actionOutput = debugOutput(localAction).indent(by: 2)
-              let stateOutput =
-                debugDiff(previousState, nextState).map { "\($0)\n" } ?? "  (No state changes)\n"
+              let actionOutput = actionFormat == .prettyPrint
+                ? debugOutput(localAction).indent(by: 2)
+                : debugCaseOutput(localAction).indent(by: 2)
+              let stateOutput = LocalState.self == Void.self
+                ? ""
+                : debugDiff(previousState, nextState).map { "\($0)\n" } ?? "  (No state changes)\n"
               debugEnvironment.printer(
                 """
                 \(prefix.isEmpty ? "" : "\(prefix): ")received action:

Sources/ComposableArchitecture/Debugging/ReducerInstrumentation.swift

@@ -87,22 +87,30 @@ extension Publisher where Failure == Never {
 }
 
 func debugCaseOutput(_ value: Any) -> String {
-  let mirror = Mirror(reflecting: value)
-  switch mirror.displayStyle {
-  case .enum:
-    guard let child = mirror.children.first else {
-      let childOutput = "\(value)"
-      return childOutput == "\(type(of: value))" ? "" : ".\(childOutput)"
-    }
-    let childOutput = debugCaseOutput(child.value)
-    return ".\(child.label ?? "")\(childOutput.isEmpty ? "" : "(\(childOutput))")"
-  case .tuple:
-    return mirror.children.map { label, value in
-      let childOutput = debugCaseOutput(value)
-      return "\(label.map { "\($0):" } ?? "")\(childOutput.isEmpty ? "" : " \(childOutput)")"
+  func debugCaseOutputHelp(_ value: Any) -> String {
+    let mirror = Mirror(reflecting: value)
+    switch mirror.displayStyle {
+    case .enum:
+      guard let child = mirror.children.first else {
+        let childOutput = "\(value)"
+        return childOutput == "\(type(of: value))" ? "" : ".\(childOutput)"
+      }
+      let childOutput = debugCaseOutputHelp(child.value)
+      return ".\(child.label ?? "")\(childOutput.isEmpty ? "" : "(\(childOutput))")"
+    case .tuple:
+      return mirror.children.map { label, value in
+        let childOutput = debugCaseOutputHelp(value)
+        return "\(label.map { isUnlabeledArgument($0) ? "_:" : "\($0):" } ?? "")\(childOutput.isEmpty ? "" : " \(childOutput)")"
+      }
+      .joined(separator: ", ")
+    default:
+      return ""
     }
-    .joined(separator: ", ")
-  default:
-    return ""
   }
+
+  return "\(type(of: value))\(debugCaseOutputHelp(value))"
+}
+
+private func isUnlabeledArgument(_ label: String) -> Bool {
+  label.firstIndex(where: { $0 != "." && !$0.isNumber }) == nil
 }

Tests/ComposableArchitectureTests/DebugTests.swift

@@ -832,4 +832,105 @@ final class DebugTests: XCTestCase {
       """
     )
   }
+
+  func testDebugCaseOutput() {
+    enum Action {
+      case action1(Bool, label: String)
+      case action2(Bool, Int, String)
+      case screenA(ScreenA)
+
+      enum ScreenA {
+        case row(index: Int, action: RowAction)
+
+        enum RowAction {
+          case tapped
+          case textChanged(query: String)
+        }
+      }
+    }
+
+    XCTAssertEqual(
+      debugCaseOutput(Action.action1(true, label: "Blob")),
+      "Action.action1(_:, label:)"
+    )
+
+    XCTAssertEqual(
+      debugCaseOutput(Action.action2(true, 1, "Blob")),
+      "Action.action2(_:, _:, _:)"
+    )
+
+    XCTAssertEqual(
+      debugCaseOutput(Action.screenA(.row(index: 1, action: .tapped))),
+      "Action.screenA(.row(index:, action: .tapped))"
+    )
+
+    XCTAssertEqual(
+      debugCaseOutput(Action.screenA(.row(index: 1, action: .textChanged(query: "Hi")))),
+      "Action.screenA(.row(index:, action: .textChanged(query:)))"
+    )
+  }
+
+  func testDebugOutput() {
+    enum Action {
+      case action1(Bool, label: String)
+      case action2(Bool, Int, String)
+      case screenA(ScreenA)
+
+      enum ScreenA {
+        case row(index: Int, action: RowAction)
+
+        enum RowAction {
+          case tapped
+          case textChanged(query: String)
+        }
+      }
+    }
+
+    XCTAssertEqual(
+      debugOutput(Action.action1(true, label: "Blob")),
+      """
+      Action.action1(
+        true,
+        label: "Blob"
+      )
+      """
+    )
+
+    XCTAssertEqual(
+      debugOutput(Action.action2(true, 1, "Blob")),
+      """
+      Action.action2(
+        true,
+        1,
+        "Blob"
+      )
+      """
+    )
+
+    XCTAssertEqual(
+      debugOutput(Action.screenA(.row(index: 1, action: .tapped))),
+      """
+      Action.screenA(
+        ScreenA.row(
+          index: 1,
+          action: RowAction.tapped
+        )
+      )
+      """
+    )
+
+    XCTAssertEqual(
+      debugOutput(Action.screenA(.row(index: 1, action: .textChanged(query: "Hi")))),
+      """
+      Action.screenA(
+        ScreenA.row(
+          index: 1,
+          action: RowAction.textChanged(
+            query: "Hi"
+          )
+        )
+      )
+      """
+    )
+  }
 }

Tests/ComposableArchitectureTests/ReducerTests.swift

@@ -157,6 +157,56 @@ final class ReducerTests: XCTestCase {
     )
   }
 
+  func testDebug_ActionFormat_OnlyLabels() {
+    enum Action: Equatable { case incr(Bool) }
+    struct State: Equatable { var count = 0 }
+
+    var logs: [String] = []
+    let logsExpectation = self.expectation(description: "logs")
+
+    let reducer = Reducer<State, Action, Void> { state, action, _ in
+      switch action {
+      case let .incr(bool):
+        state.count += bool ? 1 : 0
+        return .none
+      }
+    }
+    .debug("[prefix]", actionFormat: .labelsOnly) { _ in
+      DebugEnvironment(
+        printer: {
+          logs.append($0)
+          logsExpectation.fulfill()
+        }
+      )
+    }
+
+    let viewStore = ViewStore(
+      Store(
+        initialState: State(),
+        reducer: reducer,
+        environment: ()
+      )
+    )
+    viewStore.send(.incr(true))
+
+    self.wait(for: [logsExpectation], timeout: 2)
+
+    XCTAssertEqual(
+      logs,
+      [
+        #"""
+        [prefix]: received action:
+          Action.incr
+          State(
+        −   count: 0
+        +   count: 1
+          )
+
+        """#,
+      ]
+    )
+  }
+
   func testDefaultSignpost() {
     let reducer = Reducer<Int, Void, Void>.empty.signpost(log: .default)
     var n = 0