Support local file dependencies in JarInJar

Author: shartte

README.md

@@ -186,24 +186,6 @@ neoForge {
 
 To embed external Jar-files into your mod file, you can use the `jarJar` configuration added by the plugin.
 
-#### Subprojects
-
-For example, if you have a coremod in a subproject and want to embed its jar file, you can use the following syntax.
-
-```groovy
-dependencies {
-    jarJar project(":coremod")
-}
-```
-
-When starting the game, FML will use the group and artifact id of an embedded Jar-file to determine if the same file
-has been embedded in other mods.
-For subprojects, the group id is the root project name, while the artifact id is the name of the subproject.
-Besides the group and artifact id, the Java module name of an embedded Jar also has to be unique across all loaded
-Jar files.
-To decrease the likelihood of conflicts if no explicit module name is set,
-we prefix the filename of embedded subprojects with the group id.
-
 #### External Dependencies
 
 When you want to bundle external dependencies, Jar-in-Jar has to be able to select a single copy of that dependency
@@ -238,7 +220,69 @@ the [Maven version range format](https://cwiki.apache.org/confluence/display/MAV
 | (,1.0],[1.2,) | x <= 1.0 or x >= 1.2. Multiple sets are comma-separated                       |
 | (,1.1),(1.1,) | This excludes 1.1 if it is known not to work in combination with this library |
 
-#### External Dependencies: Runs
+#### Local Files
+
+You can also include files built by other tasks in your project, for example, jar tasks of other source sets.
+
+When wanting to build a secondary jar for a coremod or service, you could define a separate source set `service`,
+add a jar task to package it and then include the output of that jar like this:
+
+```groovy
+sourceSets {
+    service
+}
+
+
+neoForge {
+    // ...
+    mods {
+        // ...
+        // To make the service load in dev
+        'service' {
+            sourceSet sourceSets.service
+        }
+    }
+}
+
+def serviceJar = tasks.register("serviceJar", Jar) {
+    from(sourceSets.service.output)
+    manifest.attributes["FMLModType"] = "LIBRARY"
+    archiveClassifier = "service"
+    manifest {
+        attributes(
+                'FMLModType': "LIBRARY",
+                "Automatic-Module-Name": project.name + "-service"
+        )
+    }
+}
+
+dependencies {
+    jarJar files(serviceJar)
+}
+```
+
+When you include a jar file like this, we use its filename as the artifact-id and its MD5 hash as the version. 
+It will never be swapped out with embedded libraries of the same name, unless their content matches.
+
+#### Subprojects
+
+For example, if you have a coremod in a subproject and want to embed its jar file, you can use the following syntax.
+
+```groovy
+dependencies {
+    jarJar project(":coremod")
+}
+```
+
+When starting the game, FML will use the group and artifact id of an embedded Jar-file to determine if the same file
+has been embedded in other mods.
+For subprojects, the group id is the root project name, while the artifact id is the name of the subproject.
+Besides the group and artifact id, the Java module name of an embedded Jar also has to be unique across all loaded
+Jar files.
+To decrease the likelihood of conflicts if no explicit module name is set,
+we prefix the filename of embedded subprojects with the group id.
+
+### External Dependencies: Runs
 External dependencies will only be loaded in your runs if they are mods (with a `META-INF/neoforge.mods.toml` file),
 or if they have the `FMLModType` entry set in their `META-INF/MANIFEST.MF` file.
 Usually, Java libraries do not fit either of these requirements,

src/main/java/net/neoforged/moddevgradle/internal/utils/FileUtils.java

@@ -1,17 +1,27 @@
 package net.neoforged.moddevgradle.internal.utils;
 
+import org.gradle.api.GradleException;
 import org.jetbrains.annotations.ApiStatus;
 
+import java.io.File;
+import java.io.FileInputStream;
 import java.io.FilterOutputStream;
 import java.io.IOException;
 import java.io.OutputStream;
+import java.lang.module.ModuleDescriptor;
 import java.nio.charset.Charset;
 import java.nio.file.AccessDeniedException;
 import java.nio.file.AtomicMoveNotSupportedException;
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.nio.file.StandardCopyOption;
+import java.security.DigestInputStream;
+import java.security.MessageDigest;
+import java.util.HexFormat;
 import java.util.List;
+import java.util.Optional;
+import java.util.jar.JarFile;
+import java.util.zip.ZipFile;
 
 @ApiStatus.Internal
 public final class FileUtils {
@@ -23,6 +33,47 @@ public final class FileUtils {
     private FileUtils() {
     }
 
+    /**
+     * Finds an explicitly defined Java module name in the given Jar file.
+     */
+    public static Optional<String> getExplicitJavaModuleName(File file) throws IOException {
+        try (var jf = new JarFile(file, false, ZipFile.OPEN_READ, JarFile.runtimeVersion())) {
+            var moduleInfoEntry = jf.getJarEntry("module-info.class");
+            if (moduleInfoEntry != null) {
+                try (var in = jf.getInputStream(moduleInfoEntry)) {
+                    return Optional.of(ModuleDescriptor.read(in).name());
+                }
+            }
+
+            var manifest = jf.getManifest();
+            if (manifest == null) {
+                return Optional.empty();
+            }
+
+            var automaticModuleName = manifest.getMainAttributes().getValue("Automatic-Module-Name");
+            if (automaticModuleName == null) {
+                return Optional.empty();
+            }
+
+            return Optional.of(automaticModuleName);
+        } catch (Exception e) {
+            throw new IOException("Failed to determine the Java module name of " + file + ": " + e, e);
+        }
+
+    }
+
+    public static String hashFile(File file, String algorithm) {
+        try {
+            MessageDigest digest = MessageDigest.getInstance(algorithm);
+            try (var input = new DigestInputStream(new FileInputStream(file), digest)) {
+                input.transferTo(OutputStream.nullOutputStream());
+            }
+            return HexFormat.of().formatHex(digest.digest());
+        } catch (Exception e) {
+            throw new GradleException("Failed to hash file " + file, e);
+        }
+    }
+
     public static void writeStringSafe(Path destination, String content, Charset charset) throws IOException {
         if (!charset.newEncoder().canEncode(content)) {
             throw new IllegalArgumentException("The given character set " + charset

src/main/java/net/neoforged/moddevgradle/tasks/JarJar.java

@@ -4,13 +4,16 @@
 import net.neoforged.jarjar.metadata.MetadataIOHandler;
 import net.neoforged.moddevgradle.internal.jarjar.JarJarArtifacts;
 import net.neoforged.moddevgradle.internal.jarjar.ResolvedJarJarArtifact;
+import net.neoforged.moddevgradle.internal.utils.FileUtils;
 import org.gradle.api.DefaultTask;
+import org.gradle.api.GradleException;
 import org.gradle.api.artifacts.Configuration;
 import org.gradle.api.file.ConfigurableFileCollection;
 import org.gradle.api.file.DirectoryProperty;
 import org.gradle.api.file.FileSystemOperations;
 import org.gradle.api.model.ObjectFactory;
 import org.gradle.api.tasks.InputFiles;
+import org.gradle.api.tasks.Internal;
 import org.gradle.api.tasks.Nested;
 import org.gradle.api.tasks.OutputDirectory;
 import org.gradle.api.tasks.SkipWhenEmpty;
@@ -22,6 +25,7 @@
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.nio.file.StandardOpenOption;
+import java.util.ArrayList;
 import java.util.Collection;
 import java.util.List;
 import java.util.regex.Matcher;
@@ -47,25 +51,67 @@ public abstract class JarJar extends DefaultTask {
     @OutputDirectory
     public abstract DirectoryProperty getOutputDirectory();
 
+    @Internal
+    public abstract DirectoryProperty getBuildDirectory();
+
     private final FileSystemOperations fileSystemOperations;
 
     @Inject
     public JarJar(FileSystemOperations fileSystemOperations) {
         this.fileSystemOperations = fileSystemOperations;
         this.getOutputDirectory().convention(getProject().getLayout().getBuildDirectory().dir("generated/" + getName()));
+        this.getBuildDirectory().convention(getProject().getLayout().getBuildDirectory());
     }
 
     @TaskAction
-    protected void run() {
-        List<ResolvedJarJarArtifact> includedJars = getJarJarArtifacts().getResolvedArtifacts().get();
+    protected void run() throws IOException {
+        List<ResolvedJarJarArtifact> includedJars = new ArrayList<>(getJarJarArtifacts().getResolvedArtifacts().get());
         fileSystemOperations.delete(spec -> spec.delete(getOutputDirectory()));
 
+        var artifactFiles = new ArrayList<>(includedJars.stream().map(ResolvedJarJarArtifact::getFile).toList());
+        // Now we have to handle pure file collection dependencies that do not have artifact ids
+        for (var file : getInputFiles()) {
+            if (!artifactFiles.contains(file)) {
+                // Determine the module-name of the file, which is also what Java will use as the unique key
+                // when it tries to load the file. No two files can have the same module name, so it seems
+                // like a fitting key for conflict resolution by JiJ.
+                var moduleName = FileUtils.getExplicitJavaModuleName(file);
+                if (moduleName.isEmpty()) {
+                    throw new GradleException("Cannot embed local file dependency " + file + " because it has no explicit Java module name.\n" +
+                                              "Please set either 'Automatic-Module-Name' in the Jar manifest, or make it an explicit Java module.\n" +
+                                              "This ensures that your file does not conflict with another mods library that has the same or a similar filename.");
+                }
+
+                // Create a hashcode to use as a version
+                var hashCode = FileUtils.hashFile(file, "MD5");
+                includedJars.add(new ResolvedJarJarArtifact(
+                        file,
+                        file.getName(),
+                        hashCode,
+                        "[" + hashCode + "]",
+                        "",
+                        moduleName.get()
+                ));
+                artifactFiles.add(file);
+            }
+        }
+
         // Only copy metadata if not empty, always delete
         if (!includedJars.isEmpty()) {
             fileSystemOperations.copy(spec -> {
                 spec.into(getOutputDirectory().dir("META-INF/jarjar"));
-                spec.from(includedJars.stream().map(ResolvedJarJarArtifact::getFile).toArray());
+                spec.from(artifactFiles.toArray());
                 for (var includedJar : includedJars) {
+                    // Warn if any included jar is using the cursemaven group.
+                    // We know that cursemaven versions are not comparable, and the same artifact might also be
+                    // available under a "normal" group and artifact from another Maven repository.
+                    // JIJ will not correctly detect the conflicting file at runtime if another mod uses the normal Maven dependency.
+                    // For a description of Curse Maven, see https://www.cursemaven.com/
+                    if ("curse.maven".equals(includedJar.getGroup())) {
+                        getLogger().warn("Embedding dependency {}:{}:{} from cursemaven using JiJ is likely to cause conflicts at runtime when other mods include the same library from a normal Maven repository.",
+                                includedJar.getGroup(), includedJar.getArtifact(), includedJar.getVersion());
+                    }
+
                     var originalName = includedJar.getFile().getName();
                     var embeddedName = includedJar.getEmbeddedFilename();
                     if (!originalName.equals(embeddedName)) {
@@ -79,8 +125,8 @@ protected void run() {
 
     @SuppressWarnings("ResultOfMethodCallIgnored")
     private Path writeMetadata(List<ResolvedJarJarArtifact> includedJars) {
-        final Path metadataPath = getJarJarMetadataPath();
-        final Metadata metadata = createMetadata(includedJars);
+        var metadataPath = getJarJarMetadataPath();
+        var metadata = createMetadata(includedJars);
 
         try {
             metadataPath.toFile().getParentFile().mkdirs();