Jar-in-Jar: Prefix Jar files embedded from subprojects to avoid JPMS module-name conflicts

src/main/java/net/neoforged/moddevgradle/internal/jarjar/JarJarArtifacts.java

@@ -7,6 +7,7 @@
 import org.gradle.api.artifacts.component.ComponentSelector;
 import org.gradle.api.artifacts.component.ModuleComponentIdentifier;
 import org.gradle.api.artifacts.component.ModuleComponentSelector;
+import org.gradle.api.artifacts.component.ProjectComponentIdentifier;
 import org.gradle.api.artifacts.result.DependencyResult;
 import org.gradle.api.artifacts.result.ResolvedArtifactResult;
 import org.gradle.api.artifacts.result.ResolvedComponentResult;
@@ -106,14 +107,28 @@ private static List<ResolvedJarJarArtifact> getIncludedJars(Set<ResolvedComponen
             String versionRange = makeOpenRange(variant);
 
             if (version != null && versionRange != null) {
-                data.add(new ResolvedJarJarArtifact(result.getFile(), version, versionRange, jarIdentifier.group(), jarIdentifier.artifact()));
+                var embeddedFilename = getEmbeddedFilename(result, jarIdentifier);
+
+                data.add(new ResolvedJarJarArtifact(result.getFile(), embeddedFilename, version, versionRange, jarIdentifier.group(), jarIdentifier.artifact()));
             }
         }
         return data.stream()
                 .sorted(Comparator.comparing(d -> d.getGroup() + ":" + d.getArtifact()))
                 .collect(Collectors.toList());
     }
 
+    private static String getEmbeddedFilename(ResolvedArtifactResult result, ContainedJarIdentifier jarIdentifier) {
+        // When we include subprojects, we add the group to the front of the filename in an attempt to avoid
+        // ambiguous module-names between jar-files embedded by different mods.
+        // Example: two mods call their submodule "coremod" and end up with a "coremod.jar", and neither set
+        // an Automatic-Module-Name.
+        String embeddedFilename = result.getFile().getName();
+        if (result.getId().getComponentIdentifier() instanceof ProjectComponentIdentifier) {
+            embeddedFilename = jarIdentifier.group() + "." + result.getFile().getName();
+        }
+        return embeddedFilename;
+    }
+
     private static void collectFromComponent(ResolvedComponentResult rootComponent, Set<ContainedJarIdentifier> knownIdentifiers, Map<ContainedJarIdentifier, String> versions, Map<ContainedJarIdentifier, String> versionRanges) {
         for (DependencyResult result : rootComponent.getDependencies()) {
             if (!(result instanceof ResolvedDependencyResult)) {

src/main/java/net/neoforged/moddevgradle/internal/jarjar/ResolvedJarJarArtifact.java

@@ -19,13 +19,15 @@
 public class ResolvedJarJarArtifact {
 
     private final File file;
+    private final String embeddedFilename;
     private final String version;
     private final String versionRange;
     private final String group;
     private final String artifact;
 
-    public ResolvedJarJarArtifact(File file, String version, String versionRange, String group, String artifact) {
+    public ResolvedJarJarArtifact(File file, String embeddedFilename, String version, String versionRange, String group, String artifact) {
         this.file = file;
+        this.embeddedFilename = embeddedFilename;
         this.version = version;
         this.versionRange = versionRange;
         this.group = group;
@@ -48,7 +50,7 @@ public ContainedVersion createContainedVersion() {
     }
 
     public ContainedJarMetadata createContainerMetadata() {
-        return new ContainedJarMetadata(createContainedJarIdentifier(), createContainedVersion(), "META-INF/jarjar/"+file.getName(), isObfuscated(file));
+        return new ContainedJarMetadata(createContainedJarIdentifier(), createContainedVersion(), "META-INF/jarjar/"+embeddedFilename, isObfuscated(file));
     }
 
     @InputFile
@@ -57,6 +59,11 @@ public File getFile() {
         return file;
     }
 
+    @Input
+    public String getEmbeddedFilename() {
+        return embeddedFilename;
+    }
+
     @Input
     public String getVersion() {
         return version;

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

@@ -24,6 +24,8 @@
 import java.nio.file.StandardOpenOption;
 import java.util.Collection;
 import java.util.List;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
 import java.util.stream.Collectors;
 
 public abstract class JarJar extends DefaultTask {
@@ -63,6 +65,13 @@ protected void run() {
             fileSystemOperations.copy(spec -> {
                 spec.into(getOutputDirectory().dir("META-INF/jarjar"));
                 spec.from(includedJars.stream().map(ResolvedJarJarArtifact::getFile).toArray());
+                for (var includedJar : includedJars) {
+                    var originalName = includedJar.getFile().getName();
+                    var embeddedName = includedJar.getEmbeddedFilename();
+                    if (!originalName.equals(embeddedName)) {
+                        spec.rename(Pattern.quote(originalName), Matcher.quoteReplacement(embeddedName));
+                    }
+                }
                 spec.from(writeMetadata(includedJars).toFile());
             });
         }