import enum cases

Author: madsodgaard

Samples/JExtractJNISampleApp/Sources/MySwiftLibrary/Vehicle.swift

@@ -0,0 +1,18 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2025 Apple Inc. and the Swift.org project authors
+// Licensed under Apache License v2.0
+//
+// See LICENSE.txt for license information
+// See CONTRIBUTORS.txt for the list of Swift.org project authors
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+//===----------------------------------------------------------------------===//
+
+public enum Vehicle {
+  case car
+  case bicycle
+}

Samples/JExtractJNISampleApp/Sources/MySwiftLibrary/swift-java.config

@@ -1,4 +1,5 @@
 {
   "javaPackage": "com.example.swift",
   "mode": "jni",
+  "logLevel": ["debug"]
 }

Sources/JExtractSwiftLib/ImportedDecls.swift

@@ -32,6 +32,7 @@ package class ImportedNominalType: ImportedDecl {
   package var initializers: [ImportedFunc] = []
   package var methods: [ImportedFunc] = []
   package var variables: [ImportedFunc] = []
+  package var cases: [ImportedEnumCase] = []
 
   init(swiftNominal: SwiftNominalTypeDeclaration) {
     self.swiftNominal = swiftNominal
@@ -46,6 +47,28 @@ package class ImportedNominalType: ImportedDecl {
   }
 }
 
+public final class ImportedEnumCase: ImportedDecl, CustomStringConvertible {
+  /// The case name
+  public var name: String
+
+  /// The enum parameters
+  var parameters: [SwiftEnumCaseParameter]
+
+  init(name: String, parameters: [SwiftEnumCaseParameter]) {
+    self.name = name
+    self.parameters = parameters
+  }
+
+  public var description: String {
+    """
+    ImportedEnumCase {
+      name: \(name),
+      parameters: \(parameters)
+    }
+    """
+  }
+}
+
 public final class ImportedFunc: ImportedDecl, CustomStringConvertible {
   /// Swift module name (e.g. the target name where a type or function was declared)
   public var module: String

Sources/JExtractSwiftLib/JNI/JNISwift2JavaGenerator+JavaBindingsPrinting.swift

@@ -125,6 +125,11 @@ extension JNISwift2JavaGenerator {
 
       printer.println()
 
+      if decl.swiftNominal.kind == .enum {
+        printEnumHelpers(&printer, decl)
+        printer.println()
+      }
+
       for initializer in decl.initializers {
         printFunctionDowncallMethods(&printer, initializer)
         printer.println()
@@ -187,6 +192,16 @@ extension JNISwift2JavaGenerator {
     }
   }
 
+  private func printEnumHelpers(_ printer: inout CodePrinter, _ decl: ImportedNominalType) {
+    printer.printBraceBlock("public enum Discriminator") { printer in
+      printer.print(
+        decl.cases.map { $0.name.uppercased() }.joined(separator: ",\n")
+      )
+    }
+
+    printer.println()
+  }
+
   private func printFunctionDowncallMethods(
     _ printer: inout CodePrinter,
     _ decl: ImportedFunc

Sources/JExtractSwiftLib/Swift2JavaVisitor.swift

@@ -65,6 +65,8 @@ final class Swift2JavaVisitor {
     case .subscriptDecl:
       // TODO: Implement
       break
+    case .enumCaseDecl(let node):
+      self.visit(enumCaseDecl: node, in: parent)
 
     default:
       break
@@ -131,6 +133,27 @@ final class Swift2JavaVisitor {
     }
   }
 
+  func visit(enumCaseDecl node: EnumCaseDeclSyntax, in typeContext: ImportedNominalType?) {
+    do {
+      for caseElement in node.elements {
+        self.log.debug("Import case \(caseElement.name) of enum \(node.qualifiedNameForDebug)")
+
+        let parameters = try caseElement.parameterClause?.parameters.map {
+          try SwiftEnumCaseParameter($0, lookupContext: translator.lookupContext)
+        }
+
+        let imported = ImportedEnumCase(
+          name: caseElement.name.text,
+          parameters: parameters ?? []
+        )
+
+        typeContext?.cases.append(imported)
+      }
+    } catch {
+      self.log.debug("Failed to import: \(node.qualifiedNameForDebug); \(error)")
+    }
+  }
+
   func visit(variableDecl node: VariableDeclSyntax, in typeContext: ImportedNominalType?) {
     guard node.shouldExtract(config: config, log: log) else {
       return

Sources/JExtractSwiftLib/SwiftTypes/SwiftEnumCaseParameter.swift

@@ -0,0 +1,33 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2025 Apple Inc. and the Swift.org project authors
+// Licensed under Apache License v2.0
+//
+// See LICENSE.txt for license information
+// See CONTRIBUTORS.txt for the list of Swift.org project authors
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+//===----------------------------------------------------------------------===//
+
+import SwiftSyntax
+
+struct SwiftEnumCaseParameter: Equatable {
+  var name: String?
+  var type: SwiftType
+}
+
+extension SwiftEnumCaseParameter {
+  init(
+    _ node: EnumCaseParameterSyntax,
+    lookupContext: SwiftTypeLookupContext
+  ) throws {
+
+    self.init(
+      name: node.firstName?.text,
+      type: try SwiftType(node.type, lookupContext: lookupContext)
+    )
+  }
+}