jextract/jni: Skip generating empty JNI cache enums (#690)

Author: sidepelican

Samples/SwiftJavaExtractJNISampleApp/Sources/MySwiftLibrary/EnumWithValueCases.swift

@@ -14,4 +14,5 @@
 
 public enum EnumWithValueCases {
   case firstCase(UInt)
+  case secondCase
 }

Sources/JExtractSwiftLib/JNI/JNICaching.swift

@@ -28,4 +28,8 @@ enum JNICaching {
   static func cacheMemberName(for enumCase: ImportedEnumCase) -> String {
     "\(enumCase.enumType.nominalTypeDecl.name.firstCharacterLowercased)\(enumCase.name.firstCharacterUppercased)Cache"
   }
+
+  static func cacheMemberName(for translatedEnumCase: JNISwift2JavaGenerator.TranslatedEnumCase) -> String {
+    cacheMemberName(for: translatedEnumCase.original)
+  }
 }

Sources/JExtractSwiftLib/JNI/JNISwift2JavaGenerator+JavaBindingsPrinting.swift

@@ -506,10 +506,10 @@ extension JNISwift2JavaGenerator {
       // Print record
       printer.printBraceBlock("public record \(caseName)(\(members.joined(separator: ", "))) implements Case") {
         printer in
-        let nativeParameters = zip(translatedCase.translatedValues, translatedCase.parameterConversions).flatMap {
+        let nativeParameters = zip(translatedCase.translatedValues, translatedCase.parameterConversions).map {
           value,
           conversion in
-          ["\(conversion.native.javaType) \(value.parameter.name)"]
+          "\(conversion.native.javaType) \(value.parameter.name)"
         }
 
         printer.print("record _NativeParameters(\(nativeParameters.joined(separator: ", "))) {}")

Sources/JExtractSwiftLib/JNI/JNISwift2JavaGenerator+SwiftThunkPrinting.swift

@@ -174,11 +174,17 @@ extension JNISwift2JavaGenerator {
   }
 
   private func printJNICache(_ printer: inout CodePrinter, _ type: ImportedNominalType) {
+    let targetCases = type.cases
+      .compactMap(translatedEnumCase(for:))
+      .filter { !$0.translatedValues.isEmpty }
+    if targetCases.isEmpty {
+      return
+    }
+
     printer.printBraceBlock("enum \(JNICaching.cacheName(for: type))") { printer in
-      for enumCase in type.cases {
-        guard let translatedCase = translatedEnumCase(for: enumCase) else { continue }
+      for translatedCase in targetCases {
         printer.print(
-          "static let \(JNICaching.cacheMemberName(for: enumCase)) = \(renderEnumCaseCacheInit(translatedCase))"
+          "static let \(JNICaching.cacheMemberName(for: translatedCase)) = \(renderEnumCaseCacheInit(translatedCase))"
         )
       }
     }

Tests/JExtractSwiftTests/JNI/JNIEnumTests.swift

@@ -305,6 +305,12 @@ struct JNIEnumTests {
       .swift,
       detectChunkByInitialLines: 1,
       expectedChunks: [
+        """
+        enum _JNI_MyEnum {
+          static let myEnumSecondCache = _JNIMethodIDCache(className: "com/example/swift/MyEnum$Second$_NativeParameters", methods: [.init(name: "<init>", signature: "(Ljava/lang/String;)V")])
+          static let myEnumThirdCache = _JNIMethodIDCache(className: "com/example/swift/MyEnum$Third$_NativeParameters", methods: [.init(name: "<init>", signature: "(JI)V")])
+        }
+        """,
         """
         @_cdecl("Java_com_example_swift_MyEnum__00024getAsSecond__J")
         public func Java_com_example_swift_MyEnum__00024getAsSecond__J(environment: UnsafeMutablePointer<JNIEnv?>!, thisClass: jclass, selfPointer: jlong) -> jobject? {
@@ -335,6 +341,36 @@ struct JNIEnumTests {
           return environment.interface.NewObjectA(environment, class$, constructorID$, newObjectArgs$)
         }
         """,
+      ],
+      notExpectedChunks: [
+        "public func Java_com_example_swift_MyEnum__00024getAsFirst__J("
+      ]
+    )
+  }
+
+  @Test
+  func nonGeneratesGetAsCase_swift() throws {
+    try assertOutput(
+      input: """
+        public enum MyEnum {
+          case first
+          case second
+        }
+        """,
+      .jni,
+      .swift,
+      detectChunkByInitialLines: 1,
+      expectedChunks: [],
+      notExpectedChunks: [
+        """
+        enum _JNI_MyEnum
+        """,
+        """
+        public func Java_com_example_swift_MyEnum__00024getAsFirst__J("
+        """,
+        """
+        public func Java_com_example_swift_MyEnum__00024getAsSecond__J(
+        """,
       ]
     )
   }