Adds support for changing the attachment location of a @ComposeBodyOnChange function to the BindingReducer or a child Scope Reducer.

Sources/TCAComposer/Macros/ComposeMacros.swift

@@ -182,8 +182,25 @@ public macro ComposeBodyActionAlertCase(_ name: String = "") =
     module: "TCAComposerMacros", type: "ComposeDirectiveMacro"
   )
 
+/// Specified the location in the `body` to attach the `.onChange()` modifier.
+public enum ComposeBodyOnChangeAttachment {
+  // Attaches the `.onChange()` modifier to the `BindingReducer`
+  case binding
+
+  // Attaches the `.onChange()` modifier to the reducer core.
+  case core
+
+  // Attaches the `.onChange()` modifier to the `Scope` reducer for the specified child.
+  case scope(String)
+}
+
+/// Adds an `onChange(of: ...)` modifier to the `body` of the Reducer.
+/// - Parameters:
+///   - of: A `KeyPath` of `State` to use in calling the `.onChange()` modifier
+///   - attachment: Specified which Reducer in the `body` to attach the `.onChange()` to. By default it will be attached to the core.
+///
 @attached(peer)
-public macro ComposeBodyOnChange<State, Value>(of keyPath: KeyPath<State, Value>) =
+public macro ComposeBodyOnChange<State, Value>(of keyPath: KeyPath<State, Value>, attachment: ComposeBodyOnChangeAttachment = .core) =
   #externalMacro(
     module: "TCAComposerMacros", type: "ComposeDirectiveMacro"
   )

Sources/TCAComposerMacros/Composition.swift

@@ -5,6 +5,7 @@ import SwiftSyntaxBuilder
 import SwiftSyntaxMacroExpansion
 import SwiftSyntaxMacros
 import XCTestDynamicOverlay
+import OrderedCollections
 
 class Composition {
   var options = Set<Option>()
@@ -28,10 +29,11 @@ class Composition {
   var bodyCoreMembers = [BodyMember]()
   var bodyCoreModifiers = [BodyMember]()
   var bodyAfterCoreMembers = [BodyMember]()
+  var bindingReducer: BodyMember?
 
   // Reducers that need to be be converted to BodyMembers
   // after @ComposeBodyReducerChild macros have been processed
-  var childReducers = [ScopedChildReducer]()
+  var childReducers = OrderedDictionary<String, ScopedChildReducer>()
   var childBodyReducers = [ScopedChildReducer]()
 
   // Preserve a reference to the source of the child delcartaion for diagnostics.
@@ -276,6 +278,10 @@ class Composition {
       }
     }
 
+    if isBindable {
+        bindingReducer = .init(name: Identifiers.BindingReducer)
+    }
+
     if let initialStateCaseExpr {
       let caseName = initialStateCaseExpr.segments.trimmedDescription
       guard let stateMember = stateMembers.first(where: { $0.name == caseName }) else {
@@ -320,15 +326,15 @@ class Composition {
 
     // Add scopes if not enum
     if !isStateEnum || bodyCoreMembers.isEmpty {
-      bodyBeforeCoreMembers.insert(contentsOf: childReducers.map { $0.reducerBuilderMember }, at: 0)
+      bodyBeforeCoreMembers.insert(contentsOf: childReducers.values.map { $0.reducerBuilderMember }, at: 0)
     }
     else {
-      bodyCoreModifiers.insert(contentsOf: childReducers.map { $0.coreBodyModifier }, at: 0)
+      bodyCoreModifiers.insert(contentsOf: childReducers.values.map { $0.coreBodyModifier }, at: 0)
     }
 
-    if isBindable {
+    if let bindingReducer {
       actionMembers.append(.init(name: "binding", type: "BindingAction<State>"))
-      bodyBeforeCoreMembers.insert(.init(name: Identifiers.BindingReducer), at: 0)
+      bodyBeforeCoreMembers.insert(bindingReducer, at: 0)
       // TODO: handle conformance and attributes for Action here
     }
 
@@ -702,10 +708,10 @@ class Composition {
             self?.reducer(for: name)
           })
       } else {
-        childReducers.append(
+        childReducers[name] =
           ScopedChildReducer(name: name) { [weak self] in
             self?.reducer(for: name)
-          })
+          }
       }
 
     case "state":

Sources/TCAComposerMacros/ReducerAnalyzer.swift

@@ -403,7 +403,8 @@ final class ReducerAnalyzer: SyntaxVisitor {
     }
 
     var stateKeyPath = ""
-
+    var attachment: ComposeBodyOnChangeAttachment?
+
     for argument in argumentList {
       switch argument.label?.text {
       case "of":
@@ -419,9 +420,46 @@ final class ReducerAnalyzer: SyntaxVisitor {
               )
             )
           )
-          continue
+          return
         }
         stateKeyPath = "\\\(keyPath.dropFirst(6))"
+      case "attachment":
+        attachment = .init(argument.expression.trimmedDescription)
+        switch attachment {
+        case .binding:
+          guard composition.bindingReducer != nil else {
+            composition.context.diagnose(
+              Diagnostic(
+                node: argument.expression,
+                message: MacroExpansionErrorMessage(
+                """
+                `.binding` attachment requires the Reducer have the `.bindable` option specified.
+                """
+                )
+              )
+            )
+            return
+          }
+
+        case let .scope(name):
+          guard composition.childReducers[name] != nil else {
+            composition.context.diagnose(
+              Diagnostic(
+                node: argument.expression,
+                message: MacroExpansionErrorMessage(
+                """
+                '\(name)' is not a valid scoped child reducer name.
+                """
+                )
+              )
+            )
+            return
+          }
+
+        default:
+          break
+        }
+
       default:
         XCTFail(
           """
@@ -458,7 +496,27 @@ final class ReducerAnalyzer: SyntaxVisitor {
       closure: closure
     )
 
-    composition.bodyCoreModifiers.append(onChange)
+    switch attachment {
+    case .binding:
+      guard var bindingReducer = composition.bindingReducer else {
+        XCTFail("Binding reducer unexpectedly not found")
+        return
+      }
+      bindingReducer.modifiers.append(onChange)
+      composition.bindingReducer = bindingReducer
+
+    case let .scope(childName):
+      guard var childReducer = composition.childReducers[childName] else {
+        XCTFail("Child reducer unexpectedly not found")
+        return
+      }
+      childReducer.modifiers.append(onChange)
+      composition.childReducers[childName] = childReducer
+
+    case nil,
+        .core:
+      composition.bodyCoreModifiers.append(onChange)
+    }
   }
 
   func processActionCase(_ node: EnumDeclSyntax, attribute: AttributeSyntax) {

Sources/TCAComposerMacros/SharedTypes.swift

@@ -42,15 +42,22 @@ struct BodyMember {
   let name: TokenSyntax
   @LabeledExprListBuilder let argumentList: () -> LabeledExprListSyntax
   let closure: ClosureExprSyntax?
-
+  var modifiers: [BodyMember]
+
   var reducerBuilder: FunctionCallExprSyntax {
-    FunctionCallExprSyntax(
+    var builder = FunctionCallExprSyntax(
       callee: DeclReferenceExprSyntax(
         baseName: name
       ),
       trailingClosure: closure,
       argumentList: argumentList
     )
+
+    for modifier in modifiers {
+      builder = modifier.modify(wrap: builder)
+    }
+
+    return builder
   }
 
   enum Position: String {
@@ -62,11 +69,13 @@ struct BodyMember {
   init(
     name: TokenSyntax,
     @LabeledExprListBuilder argumentList: @escaping () -> LabeledExprListSyntax = { [] },
-    closure: ClosureExprSyntax? = nil
+    closure: ClosureExprSyntax? = nil,
+    modifiers: [BodyMember] = []
   ) {
     self.name = name
     self.argumentList = argumentList
     self.closure = closure
+    self.modifiers = modifiers
   }
 
   func modify(wrap: FunctionCallExprSyntax) -> FunctionCallExprSyntax {
@@ -86,12 +95,35 @@ struct BodyMember {
   }
 }
 
+enum ComposeBodyOnChangeAttachment {
+  case binding
+  case core
+  case scope(String)
+
+  init?(_ value: String) {
+    switch value {
+    case ".binding":
+      self = .binding
+
+    case ".core":
+      self = .core
+
+    case let scope where scope.hasPrefix(".scope(\""):
+      self = .scope(String(scope.dropFirst(8).dropLast(2)))
+
+    default:
+      return nil
+    }
+  }
+}
+
 struct ScopedChildReducer {
   let name: String
   let keyPaths: ScopeKeyPaths
   let reducer: (() -> FunctionCallExprSyntax?)?
   let functionName: TokenSyntax
-
+  var modifiers = [BodyMember]()
+
   init(
     name: String,
     functionName: TokenSyntax = Identifiers.Scope,
@@ -139,7 +171,8 @@ struct ScopedChildReducer {
         }
         LabeledExprSyntax(label: "action", expression: keyPaths.actionSyntax)
       },
-      closure: closure)
+      closure: closure,
+      modifiers: modifiers)
   }
 }
 

TCAComposer.xcworkspace/xcshareddata/swiftpm/Package.resolved

@@ -14,8 +14,8 @@
       "kind" : "remoteSourceControl",
       "location" : "https://github.com/pointfreeco/swift-case-paths",
       "state" : {
-        "revision" : "e072139e13f2f3e582251b49835abcf3421ac69a",
-        "version" : "1.2.3"
+        "revision" : "551150d5e60e3be78972607d89cd69069cca3e7c",
+        "version" : "1.2.4"
       }
     },
     {
@@ -32,17 +32,17 @@
       "kind" : "remoteSourceControl",
       "location" : "https://github.com/apple/swift-collections",
       "state" : {
-        "revision" : "d029d9d39c87bed85b1c50adee7c41795261a192",
-        "version" : "1.0.6"
+        "revision" : "94cf62b3ba8d4bed62680a282d4c25f9c63c2efb",
+        "version" : "1.1.0"
       }
     },
     {
       "identity" : "swift-composable-architecture",
       "kind" : "remoteSourceControl",
       "location" : "https://github.com/pointfreeco/swift-composable-architecture",
       "state" : {
-        "revision" : "96ce68db884033c4b8ae251cdf11bb47a3e5250f",
-        "version" : "1.7.2"
+        "revision" : "856f9b8d82f6851b7f61ec4c5ce9e4c18ebbdb45",
+        "version" : "1.8.2"
       }
     },
     {
@@ -59,8 +59,8 @@
       "kind" : "remoteSourceControl",
       "location" : "https://github.com/pointfreeco/swift-custom-dump",
       "state" : {
-        "revision" : "aedcf6f4cd486ccef5b312ccac85d4b3f6e58605",
-        "version" : "1.1.2"
+        "revision" : "6ea3b1b6a4957806d72030a32360d4bcb155a0d2",
+        "version" : "1.2.0"
       }
     },
     {
@@ -104,8 +104,8 @@
       "kind" : "remoteSourceControl",
       "location" : "https://github.com/pointfreeco/swift-snapshot-testing",
       "state" : {
-        "revision" : "8e68404f641300bfd0e37d478683bb275926760c",
-        "version" : "1.15.2"
+        "revision" : "e7b77228b34057041374ebef00c0fd7739d71a2b",
+        "version" : "1.15.3"
       }
     },
     {