jextract: resolve cross-module types via --depends-on

Plugins/JExtractSwiftPlugin/JExtractSwiftPlugin.swift

@@ -20,9 +20,14 @@ private let SwiftJavaConfigFileName = "swift-java.config"
 @main
 struct JExtractSwiftBuildToolPlugin: SwiftJavaPluginProtocol, BuildToolPlugin {
 
-  struct DependentConfigFile {
+  struct DependencyConfigFile {
     let swiftModuleName: String
+    // The specific URL of a swift-java.config file
     let configURL: URL
+    // Specific path of sources of this module, usually the same directory where
+    // swift-java.config is but not always. This can be passed as --depends-on
+    // if swiftpm cannot find the location automatically though module dependency
+    let sourceDirURL: URL?
   }
 
   var pluginName: String = "swift-java"
@@ -58,7 +63,7 @@ struct JExtractSwiftBuildToolPlugin: SwiftJavaPluginProtocol, BuildToolPlugin {
     let outputJavaDirectory = context.outputJavaDirectory
     let outputSwiftDirectory = context.outputSwiftDirectory
 
-    let dependentConfigFiles = searchForDependentConfigFiles(in: target)
+    let dependencyConfigFiles = searchForDependencyConfigFiles(in: target)
 
     var arguments: [String] = [
       /*subcommand=*/"jextract",
@@ -83,13 +88,14 @@ struct JExtractSwiftBuildToolPlugin: SwiftJavaPluginProtocol, BuildToolPlugin {
       arguments += ["--static-build-config", resolvedURL.absoluteURL.path(percentEncoded: false)]
     }
 
-    let dependentConfigFilesArguments = dependentConfigFiles.flatMap { dependentConfigFile in
-      [
-        "--depends-on",
-        "\(dependentConfigFile.swiftModuleName)=\(dependentConfigFile.configURL.path(percentEncoded: false))",
-      ]
+    let dependsOnArguments = dependencyConfigFiles.flatMap { dependencyConfigFile -> [String] in
+      makeDependsOnArgument(
+        moduleName: dependencyConfigFile.swiftModuleName,
+        configPath: dependencyConfigFile.configURL.path(percentEncoded: false),
+        sourcePaths: dependencyConfigFile.sourceDirURL.map { [$0.path(percentEncoded: false)] } ?? []
+      )
     }
-    arguments += dependentConfigFilesArguments
+    arguments += dependsOnArguments
 
     let swiftFiles = sourceModule.sourceFiles.map { $0.url }.filter {
       $0.pathExtension == "swift"
@@ -249,7 +255,7 @@ struct JExtractSwiftBuildToolPlugin: SwiftJavaPluginProtocol, BuildToolPlugin {
       "--output-directory", outputSwiftDirectory.path(percentEncoded: false),
       "--single-swift-file-output", singleSwiftFileOutputName,
     ]
-    javaCallbacksArguments += dependentConfigFilesArguments
+    javaCallbacksArguments += dependsOnArguments
 
     commands += [
       .buildCommand(
@@ -275,8 +281,8 @@ struct JExtractSwiftBuildToolPlugin: SwiftJavaPluginProtocol, BuildToolPlugin {
 
   /// Find the manifest files from other swift-java executions in any targets
   /// this target depends on.
-  func searchForDependentConfigFiles(in target: any Target) -> [DependentConfigFile] {
-    var dependentConfigFiles: [DependentConfigFile] = []
+  func searchForDependencyConfigFiles(in target: any Target) -> [DependencyConfigFile] {
+    var dependencyConfigFiles: [DependencyConfigFile] = []
 
     func _searchForConfigFiles(in target: any Target) {
       // log("Search for config files in target: \(target.name)")
@@ -291,8 +297,12 @@ struct JExtractSwiftBuildToolPlugin: SwiftJavaPluginProtocol, BuildToolPlugin {
         .path(percentEncoded: false)
 
       if FileManager.default.fileExists(atPath: dependencyConfigString) {
-        dependentConfigFiles.append(
-          DependentConfigFile(swiftModuleName: target.name, configURL: dependencyConfigURL)
+        dependencyConfigFiles.append(
+          DependencyConfigFile(
+            swiftModuleName: target.name,
+            configURL: dependencyConfigURL,
+            sourceDirURL: target.sourceModule?.directoryURL,
+          )
         )
       }
     }
@@ -322,7 +332,7 @@ struct JExtractSwiftBuildToolPlugin: SwiftJavaPluginProtocol, BuildToolPlugin {
       _searchForConfigFiles(in: dependency)
     }
 
-    return dependentConfigFiles
+    return dependencyConfigFiles
   }
 
   private func findSwiftJavaDirectory(for target: any Target) -> URL? {

Plugins/PluginsShared/DependsOnArgument.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
+//
+//===----------------------------------------------------------------------===//
+
+/// Build a single `--depends-on` argument pair: `["--depends-on", "<value>"]`.
+///
+/// Value form: `[<ModuleName>=]<configPath>[,<sourcePath>...]`.
+func makeDependsOnArgument(
+  moduleName: String? = nil,
+  configPath: String,
+  sourcePaths: [String] = []
+) -> [String] {
+  var value: String
+  if let moduleName, !moduleName.isEmpty {
+    value = "\(moduleName)=\(configPath)"
+  } else {
+    value = configPath
+  }
+  if !sourcePaths.isEmpty {
+    value += "," + sourcePaths.joined(separator: ",")
+  }
+  return ["--depends-on", value]
+}

Plugins/SwiftJavaPlugin/SwiftJavaPlugin.swift

@@ -19,7 +19,7 @@ private let SwiftJavaConfigFileName = "swift-java.config"
 
 @main
 struct SwiftJavaBuildToolPlugin: SwiftJavaPluginProtocol, BuildToolPlugin {
-  struct DependentConfigFile {
+  struct DependencyConfigFile {
     let swiftModuleName: String
     let configURL: URL
   }
@@ -50,7 +50,7 @@ struct SwiftJavaBuildToolPlugin: SwiftJavaPluginProtocol, BuildToolPlugin {
 
     /// Find the manifest files from other swift-java executions in any targets
     /// this target depends on.
-    var dependentConfigFiles: [DependentConfigFile] = []
+    var dependencyConfigFiles: [DependencyConfigFile] = []
     func searchForConfigFiles(in target: any Target) {
       // log("Search for config files in target: \(target.name)")
       let dependencyURL = target.directoryURL
@@ -64,8 +64,8 @@ struct SwiftJavaBuildToolPlugin: SwiftJavaPluginProtocol, BuildToolPlugin {
         .path(percentEncoded: false)
 
       if FileManager.default.fileExists(atPath: dependencyConfigString) {
-        dependentConfigFiles.append(
-          DependentConfigFile(swiftModuleName: target.name, configURL: dependencyConfigURL)
+        dependencyConfigFiles.append(
+          DependencyConfigFile(swiftModuleName: target.name, configURL: dependencyConfigURL)
         )
       }
     }
@@ -98,7 +98,7 @@ struct SwiftJavaBuildToolPlugin: SwiftJavaPluginProtocol, BuildToolPlugin {
     var arguments: [String] = []
     arguments += argumentsSwiftModule(sourceModule: sourceModule)
     arguments += argumentsOutputDirectory(context: context)
-    arguments += argumentsDependedOnConfigs(dependentConfigFiles)
+    arguments += dependsOnArguments(dependencyConfigFiles)
 
     let classes = config.classes ?? [:]
     print("[swift-java-plugin] Classes to wrap (\(classes.count)): \(classes.map(\.key))")
@@ -230,12 +230,12 @@ extension SwiftJavaBuildToolPlugin {
     ]
   }
 
-  func argumentsDependedOnConfigs(_ dependentConfigFiles: [DependentConfigFile]) -> [String] {
-    dependentConfigFiles.flatMap { dependentConfigFile in
-      [
-        "--depends-on",
-        "\(dependentConfigFile.swiftModuleName)=\(dependentConfigFile.configURL.path(percentEncoded: false))",
-      ]
+  func dependsOnArguments(_ dependencyConfigFiles: [DependencyConfigFile]) -> [String] {
+    dependencyConfigFiles.flatMap { dependencyConfigFile in
+      makeDependsOnArgument(
+        moduleName: dependencyConfigFile.swiftModuleName,
+        configPath: dependencyConfigFile.configURL.path(percentEncoded: false)
+      )
     }
   }
 

Samples/SwiftJavaExtractJNISampleApp/Package.swift

@@ -14,15 +14,20 @@ let package = Package(
       name: "MySwiftLibrary",
       type: .dynamic,
       targets: ["MySwiftLibrary"]
-    )
-
+    ),
+    .library(
+      name: "MySwiftDependencyLibrary",
+      type: .dynamic,
+      targets: ["MySwiftDependencyLibrary"]
+    ),
   ],
   dependencies: [
     .package(name: "swift-java", path: "../../")
   ],
   targets: [
+    // Separate module to show that we can handle cross module type references (automatic --depends-on)
     .target(
-      name: "MySwiftLibrary",
+      name: "MySwiftDependencyLibrary",
       dependencies: [
         .product(name: "SwiftJava", package: "swift-java")
       ],
@@ -35,6 +40,22 @@ let package = Package(
       plugins: [
         .plugin(name: "JExtractSwiftPlugin", package: "swift-java")
       ]
-    )
+    ),
+    .target(
+      name: "MySwiftLibrary",
+      dependencies: [
+        .product(name: "SwiftJava", package: "swift-java"),
+        "MySwiftDependencyLibrary",
+      ],
+      exclude: [
+        "swift-java.config"
+      ],
+      swiftSettings: [
+        .swiftLanguageMode(.v5)
+      ],
+      plugins: [
+        .plugin(name: "JExtractSwiftPlugin", package: "swift-java")
+      ]
+    ),
   ]
 )

Samples/SwiftJavaExtractJNISampleApp/Sources/MySwiftDependencyLibrary/ValueInDependencyModule.swift

@@ -0,0 +1,21 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2024-2025 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 struct ValueInDependencyModule {
+  public let value: Int32
+
+  public init(value: Int32) {
+    self.value = value
+  }
+}

Samples/SwiftJavaExtractJNISampleApp/Sources/MySwiftDependencyLibrary/swift-java.config

@@ -0,0 +1,4 @@
+{
+  "javaPackage": "com.example.swift.dep",
+  "mode": "jni",
+}

Samples/SwiftJavaExtractJNISampleApp/Sources/MySwiftLibrary/ConsumeValueFromOtherModule.swift

@@ -0,0 +1,21 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2024-2025 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 MySwiftDependencyLibrary
+
+// Show using a type from another module
+// This depends on --depends-on being passed correctly
+public func consumeValueFromOtherModule(_ v: ValueInDependencyModule) -> Int32 {
+  v.value + 1
+}

Samples/SwiftJavaExtractJNISampleApp/src/test/java/com/example/swift/MySwiftLibraryTest.java

@@ -18,6 +18,7 @@
 import org.junit.jupiter.api.BeforeAll;
 import org.junit.jupiter.api.Disabled;
 import org.junit.jupiter.api.Test;
+import org.swift.swiftkit.core.SwiftArena;
 
 import java.util.Arrays;
 import java.util.concurrent.CountDownLatch;
@@ -85,4 +86,13 @@ void labeledOverloads() {
         assertEquals(202, MySwiftLibrary.globalOverloadedB(200));
         assertEquals(303, MySwiftLibrary.globalOverloaded(300));
     }
+
+    @Test
+    void call_consumeValueFromOtherModule_crossModule() {
+        try (var arena = SwiftArena.ofConfined()) {
+            var value = com.example.swift.dep.ValueInDependencyModule.init(41, arena);
+            int result = MySwiftLibrary.consumeValueFromOtherModule(value);
+            assertEquals(42, result);
+        }
+    }
 }

Sources/JExtractSwiftLib/FFM/FFMSwift2JavaGenerator+SwiftThunkPrinting.swift

@@ -28,12 +28,13 @@ extension FFMSwift2JavaGenerator {
       return // no need to write any empty files, yay
     }
 
-    log.info(
-      "[swift-java] Write empty [\(self.expectedOutputSwiftFileNames.count)] 'expected' files in: \(swiftOutputDirectory)/"
+    log.debug(
+      "Write empty [\(self.expectedOutputSwiftFileNames.count)] 'expected' files in: \(swiftOutputDirectory)/"
     )
 
+    // FIXME(SwiftPM): We'd like to avoid having to write these blank files
     for expectedFileName in self.expectedOutputSwiftFileNames {
-      log.info("Write SwiftPM-'expected' empty file: \(expectedFileName.bold)")
+      log.trace("Write SwiftPM-'expected' empty file: \(expectedFileName.bold)")
 
       var printer = CodePrinter()
       printer.print("// Empty file generated on purpose")

Sources/JExtractSwiftLib/JNI/JNISwift2JavaGenerator+SwiftThunkPrinting.swift

@@ -35,12 +35,13 @@ extension JNISwift2JavaGenerator {
       return // no need to write any empty files, yay
     }
 
-    logger.info(
+    logger.debug(
       "Write empty [\(self.expectedOutputSwiftFileNames.count)] 'expected' files in: \(swiftOutputDirectory)/"
     )
 
+    // FIXME(SwiftPM): We'd like to avoid having to write these blank files
     for expectedFileName in self.expectedOutputSwiftFileNames {
-      logger.info("Write SwiftPM-'expected' empty file: \(expectedFileName.bold)")
+      logger.trace("Write SwiftPM-'expected' empty file: \(expectedFileName.bold)")
 
       var printer = CodePrinter()
       printer.print("// Empty file generated on purpose")