Implement Field and update traverse implementation to use static _fields var

Author: mrabiciu

Sources/SwiftProtobuf/Field.swift

@@ -110,6 +110,9 @@ public protocol Message: _CommonMessageConformances {
   /// normal `Equatable`. `Equatable` is provided with specific generated
   /// types.
   func isEqualTo(message: any Message) -> Bool
+    
+  /// Provides `Field` information for this `Message` type used to provide a default implementation of `traverse`
+  static var _fields: [Field<Self>] { get }
 }
 
 #if DEBUG
@@ -129,6 +132,14 @@ extension Message {
     return true
   }
 
+  /// Default traverse implementation
+  public func traverse<V: Visitor>(visitor: inout V) throws {
+    for field in Self._fields {
+      try field.traverse(message: self, visitor: &visitor)
+    }
+    try unknownFields.traverse(visitor: &visitor)
+  }
+
   /// A hash based on the message's full contents.
   public func hash(into hasher: inout Hasher) {
     var visitor = HashVisitor(hasher)

Sources/SwiftProtobuf/Message.swift

@@ -44,6 +44,9 @@ protocol FieldGenerator {
 
   /// Generate the support for traversing this field.
   func generateTraverse(printer: inout CodePrinter)
+  
+  /// Generate the field node
+  func generateFieldNode(printer: inout CodePrinter)
 
   /// Generate support for comparing this field's value.
   /// The generated code should return false in the current scope if the field's don't match.

Sources/protoc-gen-swift/FieldGenerator.swift

@@ -26,6 +26,7 @@ class MessageFieldGenerator: FieldGeneratorBase, FieldGenerator {
     private let swiftName: String
     private let underscoreSwiftName: String
     private let storedProperty: String
+    private let storedPropertyWithoutSelf: String
     private let swiftHasName: String
     private let swiftClearName: String
     private let swiftType: String
@@ -75,8 +76,10 @@ class MessageFieldGenerator: FieldGeneratorBase, FieldGenerator {
 
         if usesHeapStorage {
             storedProperty = "_storage.\(underscoreSwiftName)"
+            storedPropertyWithoutSelf = storedProperty
         } else {
             storedProperty = "self.\(hasFieldPresence ? underscoreSwiftName : swiftName)"
+            storedPropertyWithoutSelf = "\(hasFieldPresence ? underscoreSwiftName : swiftName)"
         }
 
         super.init(descriptor: descriptor)
@@ -221,4 +224,29 @@ class MessageFieldGenerator: FieldGeneratorBase, FieldGenerator {
         p.printIndented("try visitor.\(visitMethod)(\(traitsArg)value: \(varName), fieldNumber: \(number))")
         p.print("}\(suffix)")
     }
+  
+    func generateFieldNode(printer p: inout SwiftProtobufPluginLibrary.CodePrinter) {
+      let factoryMethod: String
+      let traitsArg: String
+      if isMap {
+          factoryMethod = "map"
+          traitsArg = "type: \(traitsType).self, "
+      } else {
+          let modifier = isPacked ? "packed" : isRepeated ? "repeated" : "singular"
+          factoryMethod = "\(modifier)\(fieldDescriptor.protoGenericType)"
+          traitsArg = ""
+      }
+      
+      let suffix: String
+      if isRepeated {
+        suffix = ""
+      } else if hasFieldPresence {
+        suffix = ", isUnset: { $0.\(storedPropertyWithoutSelf) == nil }"
+      } else if swiftDefaultValue != "0" && swiftDefaultValue != "false" && swiftDefaultValue != "String()" && swiftDefaultValue != "Data()" {
+        suffix = ", defaultValue: \(swiftDefaultValue)"
+      } else {
+        suffix = ""
+      }
+      p.print(".\(factoryMethod)(\(traitsArg){ $0.\(swiftName) }, fieldNumber: \(number)\(suffix)),")
+    }
 }

Sources/protoc-gen-swift/MessageFieldGenerator.swift

@@ -217,6 +217,8 @@ class MessageGenerator {
       // generateIsInitialized provides a blank line after itself.
       generateDecodeMessage(printer: &p)
       p.print()
+      generateFieldNodes(printer: &p)
+      p.print()
       generateTraverse(printer: &p)
       p.print()
       generateMessageEquality(printer: &p)
@@ -311,53 +313,53 @@ class MessageGenerator {
             p.print("}")
           }
         }
-
       }
     }
     p.print("}")
   }
 
-  /// Generates the `traverse` method for the message.
-  ///
-  /// - Parameter p: The code printer.
-  private func generateTraverse(printer p: inout CodePrinter) {
-    p.print("\(visibility)func traverse<V: \(namer.swiftProtobufModulePrefix)Visitor>(visitor: inout V) throws {")
-    p.withIndentation { p in
-      generateWithLifetimeExtension(printer: &p, throws: true) { p in
-        if let storage = storage {
-          storage.generatePreTraverse(printer: &p)
-        }
+  private func generateFieldNodes(printer p: inout CodePrinter) {
+    let visitExtensionsName = descriptor.useMessageSetWireFormat ? "extensionFieldsAsMessageSet" : "extensionFields"
 
-        let visitExtensionsName =
-          descriptor.useMessageSetWireFormat ? "visitExtensionFieldsAsMessageSet" : "visitExtensionFields"
-
-        let usesLocals = fields.reduce(false) { $0 || $1.generateTraverseUsesLocals }
-        if usesLocals {
-          p.print("""
-            // The use of inline closures is to circumvent an issue where the compiler
-            // allocates stack space for every if/case branch local when no optimizations
-            // are enabled. https://github.com/apple/swift-protobuf/issues/1034 and
-            // https://github.com/apple/swift-protobuf/issues/1182
-            """)
-        }
+    p.print("\(visibility)static let _fields: [Field<Self>] = [")
+      
+    // Use the "ambitious" ranges because for visit because subranges with no
+    // intermixed fields can be merged to reduce the number of calls for
+    // extension visitation.
+    var ranges = descriptor.ambitiousExtensionRanges.makeIterator()
+    var nextRange = ranges.next()
 
-        // Use the "ambitious" ranges because for visit because subranges with no
-        // intermixed fields can be merged to reduce the number of calls for
-        // extension visitation.
-        var ranges = descriptor.ambitiousExtensionRanges.makeIterator()
-        var nextRange = ranges.next()
-        for f in fieldsSortedByNumber {
-          while nextRange != nil && Int(nextRange!.lowerBound) < f.number {
-            p.print("try visitor.\(visitExtensionsName)(fields: _protobuf_extensionFieldValues, start: \(nextRange!.lowerBound), end: \(nextRange!.upperBound))")
-            nextRange = ranges.next()
-          }
-          f.generateTraverse(printer: &p)
-        }
-        while nextRange != nil {
-          p.print("try visitor.\(visitExtensionsName)(fields: _protobuf_extensionFieldValues, start: \(nextRange!.lowerBound), end: \(nextRange!.upperBound))")
+    p.withIndentation { p in
+      for f in fieldsSortedByNumber {
+        while nextRange != nil && Int(nextRange!.lowerBound) < f.number {
+          p.print(".\(visitExtensionsName)({ $0._protobuf_extensionFieldValues }, start: \(nextRange!.lowerBound), end: \(nextRange!.upperBound)),")
           nextRange = ranges.next()
         }
+        f.generateFieldNode(printer: &p)
+      }
+      while nextRange != nil {
+        p.print(".\(visitExtensionsName)({ $0._protobuf_extensionFieldValues }, start: \(nextRange!.lowerBound), end: \(nextRange!.upperBound)),")
+        nextRange = ranges.next()
       }
+    }
+    p.print("]")
+      
+    for oneof in oneofs {
+      oneof.generateFieldNodeStaticLet(printer: &p)
+    }
+  }
+    
+  private func generateTraverse(printer p: inout CodePrinter) {
+    // If we have an AnyMessageStorageClass we need to generate the traverse function so it can include a preTraverse call
+    guard let storage, storage is AnyMessageStorageClassGenerator else {
+      return
+    }
+    p.print("\(visibility)func traverse<V: Visitor>(visitor: inout V) throws {")
+    p.withIndentation { p in
+      p.print("try _storage.preTraverse()")
+      p.print("for field in Self._fields {")
+      p.printIndented("try field.traverse(message: self, visitor: &visitor)")
+      p.print("}")
       p.print("try unknownFields.traverse(visitor: &visitor)")
     }
     p.print("}")

Sources/protoc-gen-swift/MessageGenerator.swift

@@ -104,6 +104,11 @@ class OneofGenerator {
         func generateTraverse(printer p: inout CodePrinter) {
             oneof.generateTraverse(printer: &p, field: self)
         }
+      
+      func generateFieldNode(printer p: inout SwiftProtobufPluginLibrary.CodePrinter) {
+          oneof.generateFieldNode(printer: &p, field: self)
+      }
+
     }
 
     private let oneofDescriptor: OneofDescriptor
@@ -360,6 +365,33 @@ class OneofGenerator {
     }
 
     var generateTraverseUsesLocals: Bool { return true }
+    
+    func generateFieldNode(printer p: inout CodePrinter, field: MemberFieldGenerator) {
+        // First field in the group causes the output.
+        let group = fieldSortedGrouped[field.group]
+        guard field === group.first else { return }
+        p.print(".oneOf({ $0.\(swiftFieldName) }) {")
+        p.withIndentation { p in
+            p.print("switch $0 {")
+            for field in group {
+                p.print("case \(field.dottedSwiftName):")
+                p.printIndented("return _oneOfField_\(field.swiftName)")
+            }
+            if group.count != fields.count {
+                p.print("default:")
+                p.printIndented("return nil")
+            }
+            p.print("}")
+        }
+        p.print("},")
+    }
+    
+    func generateFieldNodeStaticLet(printer p: inout CodePrinter) {
+        for field in fieldsSortedByNumber {
+            p.print("private static let _oneOfField_\(field.swiftName): Field<Self> = .singular\(field.protoGenericType)({ $0.\(field.swiftName) }, fieldNumber: \(field.number), isUnset: { _ in false })")
+        }
+        
+    }
 
     func generateTraverse(printer p: inout CodePrinter, field: MemberFieldGenerator) {
         // First field in the group causes the output.