feat: JEP 445: Unnamed Classes and Instance Main Methods (#1633)

* feat: JEP 445: Unnamed Classes and Instance Main Methods

* fix: try avoid encoding issue in choco build

itests/karate.java

@@ -8,6 +8,7 @@
 ////DEPS com.intuit.karate:karate-netty:2.0.0
 ////DEPS com.github.maxandersen.karate:karate-netty:19e06766
 
+
 class karate {
 
     public static void main(String... args) {

itests/nakedmain.feature

@@ -0,0 +1,20 @@
+Feature: jep445
+
+Background:
+// as long as java 21 is not downloadable
+// we keep this abort in place - it should be removed
+// until then test by:
+// JBANG_JDK_VENDOR=openjdk ./karate.java jep445.feature
+* if (java.lang.System.getenv('JBANG_JDK_VENDOR') != "openjdk") karate.abort()
+
+Scenario: naked main
+When command('jbang nakedmain/noclass.java')
+Then match out == "Hello!\n"
+
+Scenario: naked main
+When command('jbang nakedmain/noclasswithargs.java hey')
+Then match out == "Hello hey\n"
+
+Scenario: naked main
+When command('jbang nakedmain/classinstance.java yo')
+Then match out == "Hello yo\n"

itests/nakedmain/classinstance.java

@@ -0,0 +1,8 @@
+//JAVA 21+
+//PREVIEW
+class classinstance {
+    void main(String... args) {
+
+        System.out.println("Hello " + args[0]);
+    }
+}

itests/nakedmain/noclass.java

@@ -0,0 +1,6 @@
+//JAVA 21+
+//PREVIEW
+
+void main() {
+    System.out.println("Hello!");
+}

itests/nakedmain/noclasswithargs.java

@@ -0,0 +1,6 @@
+//JAVA 21+
+//PREVIEW
+
+void main(String... args) {
+    System.out.println("Hello " + args[0]);
+}

src/main/java/dev/jbang/source/buildsteps/CompileBuildStep.java

@@ -281,6 +281,8 @@ protected String getSuggestedMain() {
 	protected abstract String getMainExtension();
 
 	protected Predicate<ClassInfo> getMainFinder() {
-		return pubClass -> pubClass.method("main", STRINGARRAYTYPE) != null;
+		return pubClass -> (pubClass.method("main", STRINGARRAYTYPE) != null
+				||
+				pubClass.method("main") != null);
 	}
 }

src/main/java/dev/jbang/util/Util.java

@@ -80,7 +80,7 @@ public class Util {
 	private static final String JBANG_DOWNLOAD_SOURCES = "JBANG_DOWNLOAD_SOURCES";
 
 	public static final Pattern patternMainMethod = Pattern.compile(
-			"^.*(public\\s+static|static\\s+public)\\s+void\\s+main\\s*\\(.*",
+			"^.*(public\\s+static|static\\s+public)\\s+void\\s+main\\s*\\(.*|void\\s+main\\s*\\(\\)",
 			Pattern.MULTILINE);
 
 	public static final Pattern mainClassMethod = Pattern.compile(

src/main/scripts/choco/jbang.nuspec

@@ -1,5 +1,4 @@
 <?xml version="1.0" encoding="utf-8"?>
-<!-- Do not remove this test for UTF-8: if “Ω” doesn’t appear as greek uppercase omega letter enclosed in quotation marks, you should use an editor that supports UTF-8, not this one. -->
 <package xmlns="http://schemas.microsoft.com/packaging/2015/06/nuspec.xsd">
   <metadata>
     <id>jbang</id>

src/test/java/dev/jbang/cli/TestJdk.java

@@ -14,7 +14,6 @@
 import java.nio.file.Path;
 import java.util.Arrays;
 import java.util.function.BiConsumer;
-import java.util.function.BiFunction;
 import java.util.function.Function;
 
 import org.junit.jupiter.api.BeforeEach;
@@ -442,14 +441,14 @@ private void createMockJdk(int jdkVersion, BiConsumer<Path, String> init) {
 		}
 	}
 
-
 	private void initMockJdkDirRuntime(Path jdkPath, String version) {
 		initMockJdkDir(jdkPath, version, "JAVA_RUNTIME_VERSION");
 	}
 
 	private void initMockJdkDir(Path jdkPath, String version) {
 		initMockJdkDir(jdkPath, version, "JAVA_VERSION");
 	}
+
 	private void initMockJdkDir(Path jdkPath, String version, String key) {
 		Util.mkdirs(jdkPath);
 		String rawJavaVersion = key + "=\"" + version + "\"";

src/test/java/dev/jbang/util/TestUtil.java

@@ -70,6 +70,21 @@ void testHasMainMethod() {
 
 		content = "public static\nvoid\nmain(String\nargs[]) {";
 		assertTrue(Util.hasMainMethod(content));
+
+		// the Java 21 / JEP-445
+
+		content = "class HelloWorld {\n" +
+				"\tvoid main() {\n" +
+				"\t\tSystem.out.println(\"Hello world from an instance main method o/\");\n" +
+				"\t}\n" +
+				"}";
+		assertTrue(Util.hasMainMethod(content));
+
+		content = "void main() {\n" +
+				"\t\tSystem.out.println(\"Hello world from an unnamed main method o/\");\n" +
+				"\t}\n";
+		assertTrue(Util.hasMainMethod(content));
+
 	}
 
 	@Test