Add Diagnostic to determine whether ViewAction and ReducerAction are enum

Sources/SimplexArchitectureMacrosPlugin/Reducer/ReducerMacro+memberMacro.swift

@@ -123,15 +123,31 @@ public struct ReducerMacro: MemberMacro {
         var viewAction: EnumDeclSyntax?
         var reducerAction: EnumDeclSyntax?
 
-        structDecl.memberBlock.members
-            .compactMap { $0.decl.as(EnumDeclSyntax.self) }
-            .forEach { enumDecl in
-                switch enumDecl.name.text {
-                case "ViewAction":
-                    viewAction = enumDecl
-                case "ReducerAction":
-                    reducerAction = enumDecl
-                default: return
+        try structDecl.memberBlock.members
+            .forEach {
+                guard let hasName = $0.hasName else {
+                    return
+                }
+
+                let name = hasName.name.text
+
+                if let enumDecl = $0.decl.as(EnumDeclSyntax.self) {
+                    switch name {
+                    case "ViewAction":
+                        viewAction = enumDecl
+                    case "ReducerAction":
+                        reducerAction = enumDecl
+                    default: return
+                    }
+                } else if name == "ViewAction" || name == "ReducerAction" {
+                    // ViewAction and ReducerAction must be enum
+                    throw DiagnosticsError(
+                        diagnostics: [
+                            ReducerMacroDiagnostic
+                                .actionMustBeEnum(actionName: name)
+                                .diagnose(at: hasName)
+                        ]
+                    )
                 }
             }
 

Sources/SimplexArchitectureMacrosPlugin/Reducer/ReducerMacroDiagnostic.swift

@@ -8,6 +8,7 @@ public enum ReducerMacroDiagnostic {
     case notStruct
     case duplicatedCase
     case noMatchInheritanceClause
+    case actionMustBeEnum(actionName: String)
 }
 
 extension ReducerMacroDiagnostic: DiagnosticMessage {
@@ -31,6 +32,9 @@ extension ReducerMacroDiagnostic: DiagnosticMessage {
 
         case .noMatchInheritanceClause:
             "The inheritance clause must match between ViewAction and ReducerAction"
+
+        case .actionMustBeEnum(let actionName):
+            "\(actionName) must be enum"
         }
     }
 
@@ -52,6 +56,9 @@ extension ReducerMacroDiagnostic: DiagnosticMessage {
 
         case .noMatchInheritanceClause:
             MessageID(domain: "ReducerMacroDiagnostic", id: "noMatchInheritanceClause")
+
+        case .actionMustBeEnum:
+            MessageID(domain: "ReducerMacroDiagnostic", id: "actionMustBeEnum")
         }
     }
 }

Tests/SimplexArchitectureTests/ReducerMacroTests.swift

@@ -13,6 +13,46 @@ final class ReducerMacroTests: XCTestCase {
         }
     }
 
+    func testActionMustBeEnum() {
+        assertMacro {
+            """
+            @Reducer
+            public struct MyReducer {
+                public struct ViewAction {}
+            }
+            """
+        } matches: {
+            """
+            @Reducer
+            public struct MyReducer {
+                public struct ViewAction {}
+                ┬──────────────────────────
+                ╰─ 🛑 ViewAction must be enum
+            }
+            """
+        }
+
+        assertMacro {
+            """
+            @Reducer
+            public struct MyReducer {
+                public enum ViewAction {}
+                public struct ReducerAction {}
+            }
+            """
+        } matches: {
+            """
+            @Reducer
+            public struct MyReducer {
+                public enum ViewAction {}
+                public struct ReducerAction {}
+                ┬─────────────────────────────
+                ╰─ 🛑 ReducerAction must be enum
+            }
+            """
+        }
+    }
+
     func testNoMatchInheritanceClause() {
         assertMacro {
             """
@@ -630,5 +670,51 @@ final class ReducerMacroTests: XCTestCase {
             }
             """
         }
+
+        assertMacro {
+            """
+            @Reducer
+            public struct MyReducer {
+                public enum ViewAction {
+                    case decrement(arg1: String = "", arg2: Int? = nil)
+                }
+                public enum ReducerAction {
+                    case decrement(arg1: String = "")
+                }
+            }
+            """
+        } matches: {
+            """
+            public struct MyReducer {
+                public enum ViewAction {
+                    case decrement(arg1: String = "", arg2: Int? = nil)
+                }
+                public enum ReducerAction {
+                    case decrement(arg1: String = "")
+                }
+
+                public enum Action: ActionProtocol {
+                        case decrement(arg1: String = "", arg2: Int? = nil)
+
+                        case decrement(arg1: String = "")
+                        public init(viewAction: ViewAction) {
+                            switch viewAction {
+                            case .decrement(let arg1, let arg2):
+                                self = .decrement(arg1: arg1, arg2: arg2)
+                            }
+                        }
+                        public init(reducerAction: ReducerAction) {
+                            switch reducerAction {
+                            case .decrement(let arg1):
+                                self = .decrement(arg1: arg1)
+                            }
+                        }
+                }
+            }
+
+            extension MyReducer: ReducerProtocol {
+            }
+            """
+        }
     }
 }