jextract: Support .swiftinterface files for --input-swift

Package.swift

@@ -334,7 +334,8 @@ let package = Package(
         .process("Resources")
       ],
       swiftSettings: [
-        .swiftLanguageMode(.v5)
+        .swiftLanguageMode(.v5),
+        .enableUpcomingFeature("BareSlashRegexLiterals"),
       ],
       plugins: [
         .plugin(name: "_StaticBuildConfigPlugin")

Sources/JExtractSwiftLib/FFM/FFMSwift2JavaGenerator+SwiftThunkPrinting.swift

@@ -90,7 +90,7 @@ extension FFMSwift2JavaGenerator {
         .sorted(by: { $0.qualifiedName < $1.qualifiedName })
 
       let inputFileName = "\(group.key)".split(separator: "/").last ?? "__Unknown.swift"
-      let filename = "\(inputFileName)".replacing(".swift", with: "+SwiftJava.swift")
+      let filename = "\(inputFileName)".replacing(/\.swift(interface)?/, with: "+SwiftJava.swift")
 
       // Print file header before all type thunks
       printer.print(

Sources/JExtractSwiftLib/FFM/FFMSwift2JavaGenerator.swift

@@ -91,10 +91,12 @@ package class FFMSwift2JavaGenerator: Swift2JavaGenerator {
           guard let fileName = input.path.split(separator: PATH_SEPARATOR).last else {
             return nil
           }
-          guard fileName.hasSuffix(".swift") else {
-            return nil
+          if fileName.hasSuffix(".swift") {
+            return String(fileName.replacing(".swift", with: "+SwiftJava.swift"))
+          } else if fileName.hasSuffix(".swiftinterface") {
+            return String(fileName.replacing(".swiftinterface", with: "+SwiftJava.swift"))
           }
-          return String(fileName.replacing(".swift", with: "+SwiftJava.swift"))
+          return nil
         }
       )
       // Also include filtered-out files so SwiftPM gets the empty outputs it expects

Sources/JExtractSwiftLib/JNI/JNISwift2JavaGenerator+SwiftThunkPrinting.swift

@@ -95,7 +95,7 @@ extension JNISwift2JavaGenerator {
           .sorted(by: { $0.qualifiedName < $1.qualifiedName })
 
         let inputFileName = "\(group.key)".split(separator: "/").last ?? "__Unknown.swift"
-        let filename = "\(inputFileName)".replacing(".swift", with: "+SwiftJava.swift")
+        let filename = "\(inputFileName)".replacing(/\.swift(interface)?/, with: "+SwiftJava.swift")
 
         for ty in importedTypesForThisFile {
           logger.info("Printing Swift thunks for type: \(ty.effectiveJavaName.bold)")

Sources/JExtractSwiftLib/JNI/JNISwift2JavaGenerator.swift

@@ -94,10 +94,12 @@ package class JNISwift2JavaGenerator: Swift2JavaGenerator {
           guard let fileName = input.path.split(separator: PATH_SEPARATOR).last else {
             return nil
           }
-          guard fileName.hasSuffix(".swift") else {
-            return nil
+          if fileName.hasSuffix(".swift") {
+            return String(fileName.replacing(".swift", with: "+SwiftJava.swift"))
+          } else if fileName.hasSuffix(".swiftinterface") {
+            return String(fileName.replacing(".swiftinterface", with: "+SwiftJava.swift"))
           }
-          return String(fileName.replacing(".swift", with: "+SwiftJava.swift"))
+          return nil
         }
       )
       // Also include filtered-out files so SwiftPM gets the empty outputs it expects

Sources/JExtractSwiftLib/Swift2Java.swift

@@ -50,7 +50,14 @@ public struct SwiftToJava {
     let inputPaths = inputSwift.split(separator: ",").map { URL(string: String($0))! }
     log.info("Input paths = \(inputPaths)")
 
-    let allFiles = collectAllFiles(suffix: ".swift", in: inputPaths, log: translator.log)
+    var allFiles: OrderedSet<URL> = []
+    for path in inputPaths {
+      if path.isDirectory {
+        allFiles.formUnion(collectAllFiles(suffix: ".swift", in: [path], log: translator.log))
+      } else {
+        allFiles.append(path)
+      }
+    }
 
     let hasFilters =
       !(config.swiftFilterInclude ?? []).isEmpty || !(config.swiftFilterExclude ?? []).isEmpty

Tests/JExtractSwiftTests/IfConfigTests.swift

@@ -79,7 +79,7 @@ struct IfConfigTests {
   @Test
   func overrideWithStaticBuildConfigurationFile() throws {
     try withTemporaryFile(
-      suffix: "json",
+      extension: "json",
       contents: """
         {
           "attributes": [],
@@ -159,19 +159,3 @@ struct IfConfigTests {
     )
   }
 }
-
-private func withTemporaryFile(
-  suffix: String,
-  contents: String = "",
-  in tempDirectory: URL = FileManager.default.temporaryDirectory,
-  _ perform: (URL) throws -> Void
-) throws {
-  let tempFileName = "tmp_\(UUID().uuidString).\(suffix)"
-  let tempFileURL = tempDirectory.appendingPathComponent(tempFileName)
-
-  try contents.write(to: tempFileURL, atomically: true, encoding: .utf8)
-  defer {
-    try? FileManager.default.removeItem(at: tempFileURL)
-  }
-  try perform(tempFileURL)
-}

Tests/JExtractSwiftTests/InputSwiftTests.swift

@@ -0,0 +1,107 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2026 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 Foundation
+import JExtractSwiftLib
+import SwiftJavaConfigurationShared
+import Testing
+
+@Suite
+struct InputSwiftTests {
+  let fileManager = FileManager.default
+
+  @Test(arguments: [JExtractGenerationMode.jni, .ffm])
+  func loadSwiftinterface(mode: JExtractGenerationMode) throws {
+    let tempDirectory: URL = fileManager.temporaryDirectory
+      .appending(path: "loadSwiftinterface-\(UUID())")
+    let outSwiftURL = tempDirectory.appending(path: "swift")
+    let outJavaURL = tempDirectory.appending(path: "java")
+
+    try withTemporaryFile(
+      fileName: "MyDependent",
+      extension: "swiftinterface",
+      contents: """
+        public struct Foo {}
+        """,
+      in: tempDirectory
+    ) { swiftInterfaceURL in
+      var config = Configuration()
+      config.mode = mode
+      config.javaPackage = "com.example"
+      config.inputSwiftDirectory = swiftInterfaceURL.absoluteURL.path()
+      config.swiftModule = "MySwift"
+      config.outputSwiftDirectory = outSwiftURL.absoluteURL.path()
+      config.outputJavaDirectory = outJavaURL.absoluteURL.path()
+
+      try SwiftToJava(config: config, dependentConfigs: [])
+        .run()
+    }
+
+    let javaPackageRoot =
+      outJavaURL
+      .appending(path: "com")
+      .appending(path: "example")
+    let expectedSources: [URL] = [
+      outSwiftURL.appending(path: "MySwiftModule+SwiftJava.swift"),
+      outSwiftURL.appending(path: "MyDependent+SwiftJava.swift"),
+      javaPackageRoot.appending(path: "Foo.java"),
+      javaPackageRoot.appending(path: "MySwift.java"),
+    ]
+
+    for expectedSource in expectedSources {
+      #expect(fileManager.fileExists(atPath: expectedSource.path()))
+    }
+  }
+
+  @Test(arguments: [JExtractGenerationMode.jni, .ffm])
+  func loadEmptySwiftinterface(mode: JExtractGenerationMode) throws {
+    let tempDirectory: URL = fileManager.temporaryDirectory
+      .appending(path: "loadEmptySwiftinterface-\(UUID())")
+    let outSwiftURL = tempDirectory.appending(path: "swift")
+    let outJavaURL = tempDirectory.appending(path: "java")
+
+    try withTemporaryFile(
+      fileName: "MyDependent",
+      extension: "swiftinterface",
+      contents: "",
+      in: tempDirectory
+    ) { swiftInterfaceURL in
+      var config = Configuration()
+      config.mode = mode
+      config.writeEmptyFiles = true
+      config.javaPackage = "com.example"
+      config.inputSwiftDirectory = swiftInterfaceURL.absoluteURL.path()
+      config.swiftModule = "MySwift"
+      config.outputSwiftDirectory = outSwiftURL.absoluteURL.path()
+      config.outputJavaDirectory = outJavaURL.absoluteURL.path()
+
+      try SwiftToJava(config: config, dependentConfigs: [])
+        .run()
+    }
+
+    let javaPackageRoot =
+      outJavaURL
+      .appending(path: "com")
+      .appending(path: "example")
+    let expectedSources: [URL] = [
+      outSwiftURL.appending(path: "MySwiftModule+SwiftJava.swift"),
+      outSwiftURL.appending(path: "MyDependent+SwiftJava.swift"),
+      javaPackageRoot.appending(path: "MySwift.java"),
+    ]
+
+    for expectedSource in expectedSources {
+      #expect(fileManager.fileExists(atPath: expectedSource.path()))
+    }
+  }
+}

Tests/JExtractSwiftTests/Utils.swift

@@ -0,0 +1,33 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2026 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 Foundation
+
+func withTemporaryFile(
+  fileName: String = "tmp_\(UUID().uuidString)",
+  extension: String,
+  contents: String = "",
+  in tempDirectory: URL = FileManager.default.temporaryDirectory,
+  _ perform: (URL) throws -> Void
+) throws {
+  let tempFileName = "\(fileName).\(`extension`)"
+  let tempFileURL = tempDirectory.appendingPathComponent(tempFileName)
+
+  try FileManager.default.createDirectory(at: tempDirectory, withIntermediateDirectories: true)
+  try contents.write(to: tempFileURL, atomically: true, encoding: .utf8)
+  defer {
+    try? FileManager.default.removeItem(at: tempFileURL)
+  }
+  try perform(tempFileURL)
+}