Swift2Java package plugin should fetch dependencies

[ktoso]

If we're intent on making the "write a swift app, use some java libs" workflow real we're going to need to handle dependencies. Very few libraries are just one jar, and managing this by hand is not really realistic.

So, we need to resolve and fetch dependencies. Thankfully, there's libraries which do this, options include:

Our best bet is probably the Maven resolver:

• maven resolver https://maven.apache.org/resolver/index.html / https://maven.apache.org/resolver/resolving-dependencies.html

Should be a pretty stable way to get the job done.

We can get a classpath for dependencies:

        RepositorySystem repoSystem = newRepositorySystem();
        RepositorySystemSession session = newSession( repoSystem );
        Dependency dependency =
            new Dependency( new DefaultArtifact( "org.apache.maven:maven-core:3.9.6" ), "compile" );
        RemoteRepository central = new RemoteRepository.Builder( "central", "default", "https://repo.maven.apache.org/maven2/" ).build();
        CollectRequest collectRequest = new CollectRequest();
        collectRequest.setRoot( dependency );
        collectRequest.addRepository( central );
        DependencyNode node = repoSystem.collectDependencies( session, collectRequest ).getRoot();
        DependencyRequest dependencyRequest = new DependencyRequest();
        dependencyRequest.setRoot( node );
        repoSystem.resolveDependencies( session, dependencyRequest  );
        PreorderNodeListGenerator nlg = new PreorderNodeListGenerator();
        node.accept( nlg );
        System.out.println( nlg.getClassPath() );

---

Other options

• https://ant.apache.org/ivy/

Ivy is an option, sbt used to use this, but I'm not sure how good it has been maintained.

• https://get-coursier.io/docs/api-low-level

Which has very minimal API:

import coursier._

val files = Fetch()
  .addDependencies(dep"org.tpolecat:doobie-core_2.12:0.6.0")
  .run()

but it'd pull in Scala...

[ktoso]

Ugh, so the eclipse/maven APIs are a bit of a pain to work with... maybe we can work it out though. Or look into the alternatives.

It might be also worth looking into using Gradle as an API

[ktoso]

The gradle API does still require we create a project to work on it seems. We could use a virtual file system though.

plugins {
    id("java")
}

group = "org.example"
version = "1.0-SNAPSHOT"

repositories {
    mavenCentral()
}

dependencies {
    implementation("dev.gradleplugins:gradle-api:8.10.1")
}

tasks.test {
    useJUnitPlatform()
}

import org.gradle.tooling.GradleConnector;

import java.io.*;
import java.nio.file.Files;
import java.util.Arrays;

public class Main {
    public static void main(String[] args) throws IOException {

        String[] dependencies = {
                "org.apache.commons:commons-lang3:3.12.0",
                "com.google.guava:guava:33.3.1-jre",
                "com.fasterxml.jackson.core:jackson-databind:2.18.0",
        };

        var classpath = getClasspathWithDependency(dependencies);
        System.out.println("classpath = " + classpath);
    }

    /**
     * May throw runtime exceptions including {@link org.gradle.api.internal.artifacts.ivyservice.TypedResolveException}
     * if unable to resolve a dependency.
     */
    private static String getClasspathWithDependency(String[] dependencies) throws IOException {
        File projectDir = Files.createTempDirectory("java-swift-dependencies").toFile();
        projectDir.mkdirs();

        File buildFile = new File(projectDir, "build.gradle");
        try (PrintWriter writer = new PrintWriter(buildFile)) {
            writer.println("plugins { id 'java-library' }");
            writer.println("repositories { mavenCentral() }");

            writer.println("dependencies {");
            for (String dependency : dependencies) {
                writer.println("implementation(\"" + dependency + "\")");
            }
            writer.println("}");

            writer.println("""
                    task printRuntimeClasspath {
                        def runtimeClasspath = sourceSets.main.runtimeClasspath
                        inputs.files(runtimeClasspath)
                        doLast {
                            println("CLASSPATH:${runtimeClasspath.asPath}")
                        }
                    }
                    """);
        }

        File settingsFile = new File(projectDir, "settings.gradle.kts");
        try (PrintWriter writer = new PrintWriter(settingsFile)) {
            writer.println("""
                    rootProject.name = "swift-java-resolve-dependencies-temp-project"
                    """);
        }

        var connection = GradleConnector.newConnector()
                .forProjectDirectory(projectDir)
                .connect();

        try (connection) {
            ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
            PrintStream printStream = new PrintStream(outputStream);

            connection.newBuild().forTasks(":printRuntimeClasspath")
                    .setStandardError(new NoopOutputStream())
                    .setStandardOutput(printStream)
                    .run();

            var all = outputStream.toString();
            var classpath = Arrays.stream(all.split("\n"))
                    .filter(s -> s.startsWith("CLASSPATH:"))
                    .map(s -> s.substring("CLASSPATH:".length()))
                    .findFirst().orElseThrow(() -> new RuntimeException("Could not find classpath output from ':printRuntimeClasspath' task."));
            return classpath;
        }
    }

    private static class NoopOutputStream extends OutputStream {
        @Override
        public void write(int b) throws IOException {
            // ignore
        }
    }
}

which gives us:

classpath = /private/var/folders/hn/c22y4jsn4j74mw23_kpgn88w0000gn/T/java-swift-dependencies6086000906569323692/build/classes/java/main:/private/var/folders/hn/c22y4jsn4j74mw23_kpgn88w0000gn/T/java-swift-dependencies6086000906569323692/build/resources/main:/Users/ktoso/.gradle/caches/modules-2/files-2.1/org.apache.commons/commons-lang3/3.12.0/c6842c86792ff03b9f1d1fe2aab8dc23aa6c6f0e/commons-lang3-3.12.0.jar:/Users/ktoso/.gradle/caches/modules-2/files-2.1/com.google.guava/guava/33.3.1-jre/852f8b363da0111e819460021ca693cacca3e8db/guava-33.3.1-jre.jar:/Users/ktoso/.gradle/caches/modules-2/files-2.1/com.fasterxml.jackson.core/jackson-annotations/2.18.0/9bddcc56af9d90f902ef5dba7348102cd12b04e2/jackson-annotations-2.18.0.jar:/Users/ktoso/.gradle/caches/modules-2/files-2.1/com.fasterxml.jackson.core/jackson-core/2.18.0/65e8ead7de5d8f7a53e296c363bea3182f21f925/jackson-core-2.18.0.jar:/Users/ktoso/.gradle/caches/modules-2/files-2.1/com.fasterxml.jackson.core/jackson-databind/2.18.0/8dba1f789a75fc30b59303574fe2b269afa4d3bc/jackson-databind-2.18.0.jar:/Users/ktoso/.gradle/caches/modules-2/files-2.1/com.google.guava/failureaccess/1.0.2/c4a06a64e650562f30b7bf9aaec1bfed43aca12b/failureaccess-1.0.2.jar:/Users/ktoso/.gradle/caches/modules-2/files-2.1/com.google.guava/listenablefuture/9999.0-empty-to-avoid-conflict-with-guava/b421526c5f297295adef1c886e5246c39d4ac629/listenablefuture-9999.0-empty-to-avoid-conflict-with-guava.jar:/Users/ktoso/.gradle/caches/modules-2/files-2.1/com.google.code.findbugs/jsr305/3.0.2/25ea2e8b0c338a877313bd4672d3fe056ea78f0d/jsr305-3.0.2.jar:/Users/ktoso/.gradle/caches/modules-2/files-2.1/org.checkerframework/checker-qual/3.43.0/9425eee39e56b116d2b998b7c2cebcbd11a3c98b/checker-qual-3.43.0.jar:/Users/ktoso/.gradle/caches/modules-2/files-2.1/com.google.errorprone/error_prone_annotations/2.28.0/59fc00087ce372de42e394d2c789295dff2d19f0/error_prone_annotations-2.28.0.jar:/Users/ktoso/.gradle/caches/modules-2/files-2.1/com.google.j2objc/j2objc-annotations/3.0.0/7399e65dd7e9ff3404f4535b2f017093bdb134c7/j2objc-annotations-3.0.0.jar

[ktoso]

Done in #199