Added support for automatically setting a module main class if module-info.java is part of the compilation operation and a main class was provided by the project.

src/main/java/rife/bld/instrument/ModuleMainClassAdapter.java

@@ -0,0 +1,44 @@
+/*
+ * Copyright 2001-2024 Geert Bevin (gbevin[remove] at uwyn dot com)
+ * Licensed under the Apache License, Version 2.0 (the "License")
+ */
+package rife.bld.instrument;
+
+import rife.asm.*;
+
+/**
+ * This utility class will modify a Java module {@code module-info.class} to add
+ * a module main class to its attributes.
+ *
+ * @author Geert Bevin (gbevin[remove] at uwyn dot com)
+ * @since 2.1
+ */
+public class ModuleMainClassAdapter extends ClassVisitor implements Opcodes {
+    private final String mainClass_;
+
+    /**
+     * Performs the actual modification of the module info class's bytecode.
+     *
+     * @param origBytes the bytes of the module class that should be modified
+     * @param mainClass the main class of the module
+     * @return the modified bytes
+     * @since 2.1
+     */
+    public static byte[] addModuleMainClassToBytes(byte[] origBytes, String mainClass) {
+        var cw = new ClassWriter(0);
+        new ClassReader(origBytes).accept(new ModuleMainClassAdapter(mainClass, cw), 0);
+        return cw.toByteArray();
+    }
+
+    private ModuleMainClassAdapter(String mainClass, ClassVisitor writer) {
+        super(ASM9, writer);
+        mainClass_ = mainClass.replace('.', '/');
+    }
+
+    @Override
+    public ModuleVisitor visitModule(String name, int access, String version) {
+        var module_visitor = super.visitModule(name, access, version);
+        module_visitor.visitMainClass(mainClass_);
+        return module_visitor;
+    }
+}

src/main/java/rife/bld/operations/CompileOperation.java

@@ -5,6 +5,7 @@
 package rife.bld.operations;
 
 import rife.bld.BaseProject;
+import rife.bld.instrument.ModuleMainClassAdapter;
 import rife.bld.operations.exceptions.ExitStatusException;
 import rife.tools.FileUtils;
 
@@ -34,6 +35,7 @@ public class CompileOperation extends AbstractOperation<CompileOperation> {
     private final List<File> testSourceDirectories_ = new ArrayList<>();
     private final JavacOptions compileOptions_ = new JavacOptions();
     private final List<Diagnostic<? extends JavaFileObject>> diagnostics_ = new ArrayList<>();
+    private String moduleMainClass_;
 
     /**
      * Performs the compile operation.
@@ -135,6 +137,12 @@ public class CompileOperation extends AbstractOperation<CompileOperation> {
                 diagnostics_.addAll(diagnostics.getDiagnostics());
                 executeProcessDiagnostics(diagnostics);
             }
+            var module_info_class = new File(destination, "module-info.class");
+            if (module_info_class.exists() && moduleMainClass() != null) {
+                var orig_bytes = FileUtils.readBytes(module_info_class);
+                var transformed_bytes = ModuleMainClassAdapter.addModuleMainClassToBytes(orig_bytes, moduleMainClass());
+                FileUtils.writeBytes(transformed_bytes, module_info_class);
+            }
         }
     }
 
@@ -175,7 +183,8 @@ public class CompileOperation extends AbstractOperation<CompileOperation> {
             .compileMainModulePath(project.compileMainModulePath())
             .compileTestModulePath(project.compileTestModulePath())
             .mainSourceFiles(project.mainSourceFiles())
-            .testSourceFiles(project.testSourceFiles());
+            .testSourceFiles(project.testSourceFiles())
+            .moduleMainClass(project.mainClass());
         if (project.javaRelease() != null && !compileOptions().containsRelease()) {
             compileOptions().release(project.javaRelease());
         }
@@ -428,6 +437,18 @@ public class CompileOperation extends AbstractOperation<CompileOperation> {
         return this;
     }
 
+    /**
+     * Provides the main class to use if this compilation includes @{code module-info.java}.
+     *
+     * @param name the main class of the module
+     * @return this operation instance
+     * @since 2.1
+     */
+    public CompileOperation moduleMainClass(String name) {
+        moduleMainClass_ = name;
+        return this;
+    }
+
     /**
      * Retrieves the main build destination directory.
      *
@@ -565,4 +586,15 @@ public class CompileOperation extends AbstractOperation<CompileOperation> {
     public List<Diagnostic<? extends JavaFileObject>> diagnostics() {
         return diagnostics_;
     }
+
+
+    /**
+     * Retrieves the main class to use if this compilation includes @{code module-info.java}.
+     *
+     * @return the main class to use for the module
+     * @since 2.1
+     */
+    public String moduleMainClass() {
+        return moduleMainClass_;
+    }
 }

src/test/java/rife/bld/operations/TestRunOperation.java

@@ -199,7 +199,8 @@ public class TestRunOperation {
             var compile_operation = new CompileOperation()
                 .buildMainDirectory(build_main)
                 .compileMainClasspath(List.of(build_main.getAbsolutePath()))
-                .mainSourceFiles(List.of(source_file1, source_file2));
+                .mainSourceFiles(List.of(source_file1, source_file2))
+                .moduleMainClass("pkg.Source1");
             compile_operation.execute();
             assertTrue(compile_operation.diagnostics().isEmpty());
 
@@ -209,12 +210,11 @@ public class TestRunOperation {
                 .sourceDirectories(List.of(build_main))
                 .destinationDirectory(destination_dir)
                 .destinationFileName(destination_name)
-                .manifestAttribute(Attributes.Name.MAIN_CLASS, "pkg.Source1")
                 .execute();
 
             var output = new StringBuilder();
             var run_operation = new RunOperation()
-                .module("pkg/pkg.Source1")
+                .module("pkg")
                 .modulePath(new File(destination_dir, destination_name).getAbsolutePath())
                 .outputProcessor(s -> {
                     output.append(s);