check-packages.java

import java.io.*;
import java.nio.file.*;
import java.util.*;
import java.util.jar.*;
import java.util.zip.*;

public class CheckSplitPackages {
    public static void main(String[] args) throws IOException {
        var rootDir = Paths.get(args.length > 0 ? args[0] : ".");
        System.out.println("🔍 Scanning all JARs under: " + rootDir + " (excluding test JARs)");

        var jarFiles = Files.walk(rootDir)
                .filter(p -> p.toString().endsWith(".jar"))
                .filter(p -> !p.getFileName().toString().endsWith("-tests.jar"))
                .toList();

        System.out.println("Found " + jarFiles.size() + " non-test JAR files to analyze");

        var packageMap = new HashMap<String, String>();
        var seen = new HashMap<String, Set<String>>();
        var foundConflict = false;

        for (var jarPath : jarFiles) {
            var jarName = jarPath.getFileName().toString();
            try (var jar = new JarFile(jarPath.toFile())) {
                jar.stream()
                   .filter(e -> !e.isDirectory() && e.getName().endsWith(".class"))
                   .map(e -> {
                       var pkg = e.getName().contains("/") ?
                                 e.getName().substring(0, e.getName().lastIndexOf('/')).replace('/', '.') :
                                 "";
                       return pkg;
                   })
                   .filter(pkg -> !pkg.isEmpty())
                   .forEach(pkg -> {
                       var previous = packageMap.putIfAbsent(pkg, jarName);
                       if (previous != null && !previous.equals(jarName)) {
                           var jars = seen.computeIfAbsent(pkg, k -> new LinkedHashSet<>());
                           if (jars.add(jarName)) {
                               if (jars.size() == 1) {
                                   System.out.println("🚨 Split package detected: " + pkg);
                                   System.out.println("    ↳ in: " + previous);
                                   System.out.println("    ↳ and: " + jarName);
                               } else {
                                   System.out.println("    ↳ also in: " + jarName);
                               }
                               foundConflict = true;
                           }
                       }
                   });
            }
        }

        if (!foundConflict) {
            System.out.println("✅ No split packages found!");
        } else {
            System.out.println("❌ Split packages detected — please fix before modularizing.");
            System.exit(1);
        }
    }
}