jextract/jni: Fix enums with unconvertible cases

Samples/SwiftJavaExtractJNISampleApp/Sources/MySwiftLibrary/GenericType.swift

@@ -88,6 +88,11 @@ public func makeIntGenericEnum() -> GenericEnum<Int> {
   if Bool.random() { return .foo } else { return .bar }
 }
 
+public enum GenericEnumWithValue<T> {
+  case some(T)
+  case none
+}
+
 extension MyID where T: BinaryInteger {
   // Conditional extension functions are not exported
   public func computeSomeValue() -> Int {

Sources/JExtractSwiftLib/JNI/JNISwift2JavaGenerator+JavaBindingsPrinting.swift

@@ -504,25 +504,40 @@ extension JNISwift2JavaGenerator {
     }
     printer.println()
 
-    let requiresSwiftArena = decl.cases.compactMap {
-      self.translatedEnumCase(for: $0)
-    }.contains(where: \.requiresSwiftArena)
-
-    printer.printBraceBlock("public Case getCase(\(requiresSwiftArena ? "SwiftArena swiftArena" : ""))") { printer in
-      printer.printBraceBlock("return switch (this.getDiscriminator())", .semicolonNewLine) { printer in
-        for enumCase in decl.cases {
-          guard let translatedCase = self.translatedEnumCase(for: enumCase) else {
-            continue
-          }
-          if enumCase.parameters.isEmpty {
-            printer.print(
-              "case \(enumCase.name.uppercased()) -> new Case.\(translatedCase.name)();"
-            )
-          } else {
-            let arenaArgument = translatedCase.requiresSwiftArena ? "swiftArena" : ""
-            printer.print(
-              "case \(enumCase.name.uppercased()) -> this.getAs\(translatedCase.name)(\(arenaArgument)).orElseThrow();"
-            )
+    // Ensure all cases can be generated to avoid inconsistency with the discriminator.
+    let allCasesCanBeTranslated = decl.cases.allSatisfy({
+      translatedEnumCase(for: $0) != nil
+    })
+    if !allCasesCanBeTranslated {
+      printer.print(
+        """
+        // This is unavailable because it contains unsupported cases.
+        private Case getCase() {
+          return null;
+        }
+        """
+      )
+    } else {
+      let requiresSwiftArena = decl.cases.compactMap {
+        self.translatedEnumCase(for: $0)
+      }.contains(where: \.requiresSwiftArena)
+
+      printer.printBraceBlock("public Case getCase(\(requiresSwiftArena ? "SwiftArena swiftArena" : ""))") { printer in
+        printer.printBraceBlock("return switch (this.getDiscriminator())", .semicolonNewLine) { printer in
+          for enumCase in decl.cases {
+            guard let translatedCase = self.translatedEnumCase(for: enumCase) else {
+              continue
+            }
+            if enumCase.parameters.isEmpty {
+              printer.print(
+                "case \(enumCase.name.uppercased()) -> new Case.\(translatedCase.name)();"
+              )
+            } else {
+              let arenaArgument = translatedCase.requiresSwiftArena ? "swiftArena" : ""
+              printer.print(
+                "case \(enumCase.name.uppercased()) -> this.getAs\(translatedCase.name)(\(arenaArgument)).orElseThrow();"
+              )
+            }
           }
         }
       }

Tests/JExtractSwiftTests/JNI/JNIGenericTypeTests.swift

@@ -252,6 +252,43 @@ struct JNIGenericTypeTests {
     )
   }
 
+  @Test
+  func genericEnumWithAssociatedValue() throws {
+    let input =
+      #"""
+      public enum MyOptional<Wrapped> {
+        case some(Wrapped)
+        case none
+      }
+      """#
+
+    try assertOutput(
+      input: input,
+      .jni,
+      .java,
+      detectChunkByInitialLines: 2,
+      expectedChunks: [
+        """
+        public enum Discriminator {
+          SOME,
+          NONE
+        }
+        """,
+        """
+        public sealed interface Case {
+          record None() implements Case {}
+        }
+        """,
+        """
+        // This is unavailable because it contains unsupported cases.
+        private Case getCase() {
+          return null;
+        }
+        """,
+      ]
+    )
+  }
+
   @Test
   func nestedGenericType() throws {
     let input =