refactor: Remove FlowError and move noTasksToExecute to StoreError

Examples/AdvancedPatterns/MultiStepWizard/MultiStepWizardFeature.swift

@@ -1,6 +1,21 @@
 import Flow
 import Foundation
 
+/// Application-specific errors for wizard operations.
+enum WizardError: Error, LocalizedError {
+  case validationFailed(step: String, errors: [String])
+  case submissionFailed(underlying: Error)
+
+  var errorDescription: String? {
+    switch self {
+    case .validationFailed(let step, let errors):
+      return "Validation failed in \(step): \(errors.joined(separator: ", "))"
+    case .submissionFailed(let underlying):
+      return "Submission failed: \(underlying.localizedDescription)"
+    }
+  }
+}
+
 /// Multi-step wizard/form with complex validation and navigation.
 ///
 /// Demonstrates:
@@ -39,7 +54,7 @@ struct MultiStepWizardFeature: Feature {
     // UI state
     var isValidating = false
     var isSubmitting = false
-    var error: FlowError?
+    var error: WizardError?
 
     // Validation errors per step
     var personalInfoErrors: [String] = []
@@ -219,15 +234,15 @@ struct MultiStepWizardFeature: Feature {
             // Reset wizard after successful submission
             resetWizard(state: state)
           } catch {
-            throw FlowError.networkError(underlying: error)
+            throw WizardError.submissionFailed(underlying: error)
           }
         }
         .catch { error, state in
           state.isSubmitting = false
-          if let vfError = error as? FlowError {
-            state.error = vfError
+          if let wizardError = error as? WizardError {
+            state.error = wizardError
           } else {
-            state.error = .networkError(underlying: error)
+            state.error = .submissionFailed(underlying: error)
           }
         }
 

Examples/AdvancedPatterns/NetworkingWithRetry/RetryNetworkFeature.swift

@@ -1,12 +1,27 @@
 import Flow
 import Foundation
 
+/// Application-specific errors for retry networking.
+enum RetryError: Error, LocalizedError {
+  case maxRetriesExceeded(attempts: Int)
+  case networkFailure(underlying: Error)
+
+  var errorDescription: String? {
+    switch self {
+    case .maxRetriesExceeded(let attempts):
+      return "Failed after \(attempts) retry attempts"
+    case .networkFailure(let underlying):
+      return "Network error: \(underlying.localizedDescription)"
+    }
+  }
+}
+
 /// Advanced networking feature with exponential backoff retry logic.
 ///
 /// Demonstrates:
 /// - Retry with exponential backoff
 /// - Maximum retry attempts
-/// - Error handling with FlowError
+/// - Error handling with custom error types
 /// - Task cancellation
 /// - Loading states during retries
 struct RetryNetworkFeature: Feature {
@@ -32,7 +47,7 @@ struct RetryNetworkFeature: Feature {
   final class State {
     var data: [Item]?
     var isLoading = false
-    var error: FlowError?
+    var error: RetryError?
 
     // Retry tracking
     var retryCount = 0
@@ -41,7 +56,7 @@ struct RetryNetworkFeature: Feature {
     init(
       data: [Item]? = nil,
       isLoading: Bool = false,
-      error: FlowError? = nil
+      error: RetryError? = nil
     ) {
       self.data = data
       self.isLoading = isLoading
@@ -73,9 +88,7 @@ struct RetryNetworkFeature: Feature {
 
       case .retryFetch:
         guard state.retryCount < maxRetries else {
-          state.error = .custom(
-            message: "Maximum retry attempts (\(maxRetries)) exceeded"
-          )
+          state.error = .maxRetriesExceeded(attempts: maxRetries)
           state.isLoading = false
           return .none
         }
@@ -121,7 +134,7 @@ struct RetryNetworkFeature: Feature {
           )
         } else {
           // Max retries exceeded
-          state.error = .networkError(underlying: error)
+          state.error = .networkFailure(underlying: error)
           return .none
         }
       }
@@ -152,20 +165,17 @@ struct RetryNetworkFeature: Feature {
           // Retry recursively
           try await performFetch(state: state)
         } else {
-          throw FlowError.custom(
-            message: "Failed after \(maxRetries) retries",
-            underlying: error
-          )
+          throw RetryError.maxRetriesExceeded(attempts: maxRetries)
         }
       }
     }
     .cancellable(id: "fetch-data", cancelInFlight: true)
     .catch { error, state in
       state.isLoading = false
-      if let vfError = error as? FlowError {
-        state.error = vfError
+      if let retryError = error as? RetryError {
+        state.error = retryError
       } else {
-        state.error = .networkError(underlying: error)
+        state.error = .networkFailure(underlying: error)
       }
     }
   }

Examples/AdvancedPatterns/PaginatedList/PaginatedListFeature.swift

@@ -1,6 +1,18 @@
 import Flow
 import Foundation
 
+/// Application-specific errors for pagination operations.
+enum PaginationError: Error, LocalizedError {
+  case fetchFailed(underlying: Error)
+
+  var errorDescription: String? {
+    switch self {
+    case .fetchFailed(let underlying):
+      return "Failed to fetch items: \(underlying.localizedDescription)"
+    }
+  }
+}
+
 /// Paginated list feature with infinite scrolling.
 ///
 /// Demonstrates:
@@ -28,7 +40,7 @@ struct PaginatedListFeature: Feature {
     var nextCursor: String?  // Pagination cursor
     var hasMore = true  // More pages available
 
-    var error: FlowError?
+    var error: PaginationError?
 
     init(
       items: [Item] = [],
@@ -72,16 +84,16 @@ struct PaginatedListFeature: Feature {
             state.isInitialLoading = false
             state.error = nil
           } catch {
-            throw FlowError.networkError(underlying: error)
+            throw PaginationError.fetchFailed(underlying: error)
           }
         }
         .cancellable(id: "fetch-page", cancelInFlight: true)
         .catch { error, state in
           state.isInitialLoading = false
-          if let vfError = error as? FlowError {
-            state.error = vfError
+          if let paginationError = error as? PaginationError {
+            state.error = paginationError
           } else {
-            state.error = .networkError(underlying: error)
+            state.error = .fetchFailed(underlying: error)
           }
         }
 
@@ -102,16 +114,16 @@ struct PaginatedListFeature: Feature {
             state.isRefreshing = false
             state.error = nil
           } catch {
-            throw FlowError.networkError(underlying: error)
+            throw PaginationError.fetchFailed(underlying: error)
           }
         }
         .cancellable(id: "fetch-page", cancelInFlight: true)
         .catch { error, state in
           state.isRefreshing = false
-          if let vfError = error as? FlowError {
-            state.error = vfError
+          if let paginationError = error as? PaginationError {
+            state.error = paginationError
           } else {
-            state.error = .networkError(underlying: error)
+            state.error = .fetchFailed(underlying: error)
           }
         }
 
@@ -139,16 +151,16 @@ struct PaginatedListFeature: Feature {
             state.isLoadingMore = false
             state.error = nil
           } catch {
-            throw FlowError.networkError(underlying: error)
+            throw PaginationError.fetchFailed(underlying: error)
           }
         }
         .cancellable(id: "fetch-page", cancelInFlight: true)
         .catch { error, state in
           state.isLoadingMore = false
-          if let vfError = error as? FlowError {
-            state.error = vfError
+          if let paginationError = error as? PaginationError {
+            state.error = paginationError
           } else {
-            state.error = .networkError(underlying: error)
+            state.error = .fetchFailed(underlying: error)
           }
         }
 
@@ -165,10 +177,10 @@ struct PaginatedListFeature: Feature {
         state.isRefreshing = false
         state.isLoadingMore = false
 
-        if let vfError = error as? FlowError {
-          state.error = vfError
+        if let paginationError = error as? PaginationError {
+          state.error = paginationError
         } else {
-          state.error = .networkError(underlying: error)
+          state.error = .fetchFailed(underlying: error)
         }
 
         return .none

Examples/AdvancedPatterns/README.md

@@ -9,7 +9,7 @@
 **学習内容:**
 - 指数バックオフリトライ
 - 最大リトライ回数の制御
-- FlowError によるエラーハンドリング
+- カスタムエラー型によるエラーハンドリング
 - タスクキャンセル
 - リトライ中のローディング状態
 
@@ -36,7 +36,7 @@ return .run { state in
             try await Task.sleep(for: delay)
             try await performFetch(state: state)  // 再帰的リトライ
         } else {
-            throw FlowError.custom(message: "Max retries exceeded")
+            throw RetryError.maxRetriesExceeded(attempts: maxRetries)
         }
     }
 }
@@ -215,14 +215,30 @@ struct RobustPaginatedListFeature: Feature {
 
 ### 1. エラーハンドリング
 
-全ての例で FlowError を使用：
+各機能で専用のエラー型を定義してエラーハンドリング：
 
 ```swift
+// アプリケーション固有のエラー型を定義
+enum RetryError: Error, LocalizedError {
+    case maxRetriesExceeded(attempts: Int)
+    case networkFailure(underlying: Error)
+
+    var errorDescription: String? {
+        switch self {
+        case .maxRetriesExceeded(let attempts):
+            return "Failed after \(attempts) retry attempts"
+        case .networkFailure(let underlying):
+            return "Network error: \(underlying.localizedDescription)"
+        }
+    }
+}
+
+// エラーハンドリング
 .catch { error, state in
-    if let vfError = error as? FlowError {
-        state.error = vfError
+    if let retryError = error as? RetryError {
+        state.error = retryError
     } else {
-        state.error = .networkError(underlying: error)
+        state.error = .networkFailure(underlying: error)
     }
 }
 ```
@@ -260,7 +276,7 @@ return .run { state in
 @Observable
 final class State {
     var isLoading = false
-    var error: FlowError?
+    var error: RetryError?  // アプリケーション固有のエラー型
 }
 
 // ❌ Bad: Feature に状態を持つ
@@ -290,7 +306,7 @@ swift test --filter MultiStepWizardFeature
 /// Demonstrates:
 /// - Retry with exponential backoff
 /// - Maximum retry attempts
-/// - Error handling with FlowError
+/// - Error handling with custom error types
 /// ...
 struct RetryNetworkFeature: Feature { ... }
 ```

Sources/Flow/Store/ActionTask.swift

@@ -482,7 +482,7 @@ extension ActionTask {
 
   /// Concatenates an array of tasks to run sequentially.
   ///
-  /// Throws `FlowError.noTasksToExecute` if the task array is empty.
+  /// Throws `StoreError.noTasksToExecute` if the task array is empty.
   /// This strict behavior helps catch logic errors early.
   ///
   /// ## Example: Dynamic Tasks with Guard
@@ -507,10 +507,10 @@ extension ActionTask {
   ///
   /// - Parameter tasks: Array of tasks to concatenate (must not be empty)
   /// - Returns: A single task that runs all tasks sequentially
-  /// - Throws: `FlowError.noTasksToExecute` if tasks array is empty
+  /// - Throws: `StoreError.noTasksToExecute` if tasks array is empty
   public static func concatenate(_ tasks: [ActionTask]) throws -> ActionTask {
     guard let first = tasks.first else {
-      throw FlowError.noTasksToExecute(context: "concatenate(_:)")
+      throw StoreError.noTasksToExecute(context: "concatenate(_:)")
     }
     // TCA-style reduce pattern implementing Monoid
     return tasks.dropFirst().reduce(first) { $0.concatenate(with: $1) }