jextract/jni: Refactor toString generation to use the standard method generation path (#567)

* Include toString function generation in the common method generation path

* swift format

* case synthesizedFunction(SynthesizedAPI)

* dont change parameter name to self

---------

Co-authored-by: Konrad Malawski <ktoso@apple.com>

Author: sidepelican

Sources/JExtractSwiftLib/FFM/CDeclLowering/FFMSwift2JavaGenerator+FunctionLowering.swift

@@ -993,6 +993,14 @@ extension LoweredFunctionSignature {
         .joined(separator: ", ")
       resultExpr = "\(callee)(\(raw: arguments))"
 
+    case .synthesizedFunction(let function):
+      switch function {
+      case .toString:
+        resultExpr = "String(describing: \(callee))"
+      case .toDebugString:
+        resultExpr = "String(reflecting: \(callee))"
+      }
+
     case .getter:
       assert(paramExprs.isEmpty)
       resultExpr = callee

Sources/JExtractSwiftLib/FFM/FFMSwift2JavaGenerator+JavaTranslation.swift

@@ -160,7 +160,7 @@ extension FFMSwift2JavaGenerator {
         switch decl.apiKind {
         case .getter, .subscriptGetter: decl.javaGetterName
         case .setter, .subscriptSetter: decl.javaSetterName
-        case .function, .initializer, .enumCase: decl.name
+        case .function, .synthesizedFunction, .initializer, .enumCase: decl.name
         }
 
       // Signature.

Sources/JExtractSwiftLib/ImportedDecls.swift

@@ -17,8 +17,14 @@ import SwiftSyntax
 /// Any imported (Swift) declaration
 protocol ImportedDecl: AnyObject {}
 
-package enum SwiftAPIKind {
+package enum SynthesizedAPI: Equatable {
+  case toString
+  case toDebugString
+}
+
+package enum SwiftAPIKind: Equatable {
   case function
+  case synthesizedFunction(SynthesizedAPI)
   case initializer
   case getter
   case setter
@@ -182,7 +188,7 @@ public final class ImportedFunc: ImportedDecl, CustomStringConvertible {
       case .getter: "getter:"
       case .setter: "setter:"
       case .enumCase: "case:"
-      case .function, .initializer: ""
+      case .function, .synthesizedFunction, .initializer: ""
       case .subscriptGetter: "subscriptGetter:"
       case .subscriptSetter: "subscriptSetter:"
       }

Sources/JExtractSwiftLib/JNI/JNISwift2JavaGenerator+JavaBindingsPrinting.swift

@@ -267,9 +267,6 @@ extension JNISwift2JavaGenerator {
         printer.println()
       }
 
-      printToStringMethods(&printer, decl)
-      printer.println()
-
       printSpecificTypeHelpers(&printer, decl)
 
       printTypeMetadataAddressFunction(&printer, decl)
@@ -294,28 +291,6 @@ extension JNISwift2JavaGenerator {
     }
   }
 
-  private func printToStringMethods(_ printer: inout CodePrinter, _ decl: ImportedNominalType) {
-    printer.printBraceBlock("public String toString()") { printer in
-      printer.print(
-        """
-        return $toString(this.$memoryAddress());
-        """
-      )
-    }
-    printer.print("private static native java.lang.String $toString(long selfPointer);")
-
-    printer.println()
-
-    printer.printBraceBlock("public String toDebugString()") { printer in
-      printer.print(
-        """
-        return $toDebugString(this.$memoryAddress());
-        """
-      )
-    }
-    printer.print("private static native java.lang.String $toDebugString(long selfPointer);")
-  }
-
   private func printHeader(_ printer: inout CodePrinter) {
     printer.print(
       """

Sources/JExtractSwiftLib/JNI/JNISwift2JavaGenerator+JavaTranslation.swift

@@ -213,7 +213,7 @@ extension JNISwift2JavaGenerator {
         switch decl.apiKind {
         case .getter, .subscriptGetter: decl.javaGetterName
         case .setter, .subscriptSetter: decl.javaSetterName
-        case .function, .initializer, .enumCase: decl.name
+        case .function, .synthesizedFunction, .initializer, .enumCase: decl.name
         }
 
       // Swift -> Java

Sources/JExtractSwiftLib/JNI/JNISwift2JavaGenerator+SwiftThunkPrinting.swift

@@ -271,7 +271,6 @@ extension JNISwift2JavaGenerator {
       printer.println()
     }
 
-    printToStringMethods(&printer, type)
     printSpecificTypeThunks(&printer, type)
     printTypeMetadataAddressThunk(&printer, type)
     printer.println()
@@ -286,49 +285,6 @@ extension JNISwift2JavaGenerator {
     try printSwiftInterfaceWrapper(&printer, protocolWrapper)
   }
 
-  private func printToStringMethods(_ printer: inout CodePrinter, _ type: ImportedNominalType) {
-    let selfPointerParam = JavaParameter(name: "selfPointer", type: .long)
-    let parentName = type.qualifiedName
-
-    printCDecl(
-      &printer,
-      javaMethodName: "$toString",
-      parentName: type.swiftNominal.qualifiedName,
-      parameters: [
-        selfPointerParam
-      ],
-      resultType: .javaLangString
-    ) { printer in
-      let selfVar = self.printSelfJLongToUnsafeMutablePointer(&printer, swiftParentName: parentName, selfPointerParam)
-
-      printer.print(
-        """
-        return String(describing: \(selfVar).pointee).getJNIValue(in: environment)
-        """
-      )
-    }
-
-    printer.println()
-
-    printCDecl(
-      &printer,
-      javaMethodName: "$toDebugString",
-      parentName: type.swiftNominal.qualifiedName,
-      parameters: [
-        selfPointerParam
-      ],
-      resultType: .javaLangString
-    ) { printer in
-      let selfVar = self.printSelfJLongToUnsafeMutablePointer(&printer, swiftParentName: parentName, selfPointerParam)
-
-      printer.print(
-        """
-        return String(reflecting: \(selfVar).pointee).getJNIValue(in: environment)
-        """
-      )
-    }
-  }
-
   private func printEnumDiscriminator(_ printer: inout CodePrinter, _ type: ImportedNominalType) {
     let selfPointerParam = JavaParameter(name: "selfPointer", type: .long)
     printCDecl(
@@ -623,6 +579,14 @@ extension JNISwift2JavaGenerator {
       .joined(separator: ", ")
       result = "\(tryClause)\(callee).\(decl.name)(\(downcallArguments))"
 
+    case .synthesizedFunction(let function):
+      switch function {
+      case .toString:
+        result = "String(describing: \(callee))"
+      case .toDebugString:
+        result = "String(reflecting: \(callee))"
+      }
+
     case .enumCase:
       let downcallArguments = zip(
         decl.functionSignature.parameters,

Sources/JExtractSwiftLib/Swift2JavaVisitor.swift

@@ -85,6 +85,8 @@ final class Swift2JavaVisitor {
     for memberItem in node.memberBlock.members {
       self.visit(decl: memberItem.decl, in: importedNominalType, sourceFilePath: sourceFilePath)
     }
+
+    self.synthesizeToStringMethods(in: importedNominalType)
   }
 
   func visit(
@@ -405,6 +407,46 @@ final class Swift2JavaVisitor {
       }
     }
   }
+
+  private func synthesizeToStringMethods(in imported: ImportedNominalType) {
+    switch imported.swiftNominal.kind {
+    case .actor, .class, .enum, .struct:
+      break
+    case .protocol:
+      return
+    }
+
+    let knownTypes = SwiftKnownTypes(symbolTable: translator.symbolTable)
+    let toStringFunctionSignature = SwiftFunctionSignature(
+      selfParameter: .instance(SwiftParameter(convention: .byValue, parameterName: "selfPointer", type: imported.swiftType)),
+      parameters: [],
+      result: SwiftResult(convention: .direct, type: knownTypes.string),
+      effectSpecifiers: [],
+      genericParameters: [],
+      genericRequirements: []
+    )
+
+    func makeToStringFunc(name: String, kind: SwiftAPIKind) -> ImportedFunc {
+      ImportedFunc(
+        module: translator.swiftModuleName,
+        swiftDecl: DeclSyntax("func \(raw: name)() -> String"),
+        name: name,
+        apiKind: kind,
+        functionSignature: toStringFunctionSignature
+      )
+    }
+
+    if !imported.methods.contains(where: {
+      $0.name == "toString" && $0.functionSignature == toStringFunctionSignature
+    }) {
+      imported.methods.append(makeToStringFunc(name: "toString", kind: .synthesizedFunction(.toString)))
+    }
+    if !imported.methods.contains(where: {
+      $0.name == "toDebugString" && $0.functionSignature == toStringFunctionSignature
+    }) {
+      imported.methods.append(makeToStringFunc(name: "toDebugString", kind: .synthesizedFunction(.toDebugString)))
+    }
+  }
 }
 
 extension DeclSyntaxProtocol where Self: WithModifiersSyntax & WithAttributesSyntax {

Tests/JExtractSwiftTests/JNI/JNIToStringTests.swift

@@ -32,13 +32,11 @@ struct JNIToStringTests {
       detectChunkByInitialLines: 1,
       expectedChunks: [
         """
-        public String toString() {
-          return $toString(this.$memoryAddress());
+        public java.lang.String toString() {
+          return MyType.$toString(this.$memoryAddress());
         }
-        """,
-        """
         private static native java.lang.String $toString(long selfPointer);
-        """,
+        """
       ]
     )
   }
@@ -55,7 +53,7 @@ struct JNIToStringTests {
         @_cdecl("Java_com_example_swift_MyType__00024toString__J")
         public func Java_com_example_swift_MyType__00024toString__J(environment: UnsafeMutablePointer<JNIEnv?>!, thisClass: jclass, selfPointer: jlong) -> jstring? {
           ...
-          return String(describing: self$.pointee).getJNIValue(in: environment)
+          return String(describing: selfPointer$.pointee).getJNIValue(in: environment)
         }
         """
       ]
@@ -71,9 +69,10 @@ struct JNIToStringTests {
       detectChunkByInitialLines: 1,
       expectedChunks: [
         """
-        public String toDebugString() {
-          return $toDebugString(this.$memoryAddress());
+        public java.lang.String toDebugString() {
+          return MyType.$toDebugString(this.$memoryAddress());
         }
+        private static native java.lang.String $toDebugString(long selfPointer);
         """
       ]
     )
@@ -91,7 +90,7 @@ struct JNIToStringTests {
         @_cdecl("Java_com_example_swift_MyType__00024toDebugString__J")
         public func Java_com_example_swift_MyType__00024toDebugString__J(environment: UnsafeMutablePointer<JNIEnv?>!, thisClass: jclass, selfPointer: jlong) -> jstring? {
           ...
-          return String(reflecting: self$.pointee).getJNIValue(in: environment)
+          return String(reflecting: selfPointer$.pointee).getJNIValue(in: environment)
         }
         """
       ]