Add GraalJS engine support alongside Nashorn

handlebars-maven-plugin/pom.xml

@@ -21,6 +21,12 @@
       <version>${project.version}</version>
     </dependency>
 
+    <dependency>
+      <groupId>org.openjdk.nashorn</groupId>
+      <artifactId>nashorn-core</artifactId>
+      <version>15.4</version>
+    </dependency>
+
     <dependency>
       <groupId>ch.qos.logback</groupId>
       <artifactId>logback-classic</artifactId>

handlebars/pom.xml

@@ -170,6 +170,23 @@
       <groupId>org.openjdk.nashorn</groupId>
       <artifactId>nashorn-core</artifactId>
       <version>${nashorn.version}</version>
+      <optional>true</optional>
+    </dependency>
+
+    <dependency>
+      <groupId>org.graalvm.js</groupId>
+      <artifactId>js-scriptengine</artifactId>
+      <version>${graaljs.version}</version>
+      <optional>true</optional>
+    </dependency>
+
+    <dependency>
+      <groupId>org.graalvm.polyglot</groupId>
+      <artifactId>js</artifactId>
+      <version>${graaljs.version}</version>
+      <type>pom</type>
+      <scope>runtime</scope>
+      <optional>true</optional>
     </dependency>
 
     <dependency>
@@ -240,6 +257,7 @@
 
   <properties>
     <nashorn.version>15.4</nashorn.version>
+    <graaljs.version>25.0.3</graaljs.version>
   </properties>
 
   <profiles>
@@ -300,5 +318,55 @@
         </plugins>
       </build>
     </profile>
+
+    <profile>
+      <id>graaljs-jit</id>
+      <dependencies>
+        <dependency>
+          <groupId>org.graalvm.compiler</groupId>
+          <artifactId>compiler</artifactId>
+          <version>${graaljs.version}</version>
+          <scope>test</scope>
+        </dependency>
+      </dependencies>
+      <build>
+        <plugins>
+          <plugin>
+            <groupId>org.apache.maven.plugins</groupId>
+            <artifactId>maven-dependency-plugin</artifactId>
+            <executions>
+              <execution>
+                <id>graal-compiler-path</id>
+                <phase>initialize</phase>
+                <goals>
+                  <goal>properties</goal>
+                </goals>
+              </execution>
+              <execution>
+                <id>copy-graaljs-modules</id>
+                <phase>generate-test-resources</phase>
+                <goals>
+                  <goal>copy-dependencies</goal>
+                </goals>
+                <configuration>
+                  <outputDirectory>${project.build.directory}/graaljs-modules</outputDirectory>
+                  <includeGroupIds>org.graalvm.polyglot,org.graalvm.js,org.graalvm.truffle,org.graalvm.sdk,org.graalvm.regex,org.graalvm.shadowed</includeGroupIds>
+                  <excludeArtifactIds>compiler</excludeArtifactIds>
+                  <excludeTypes>pom</excludeTypes>
+                </configuration>
+              </execution>
+            </executions>
+          </plugin>
+          <plugin>
+            <groupId>org.apache.maven.plugins</groupId>
+            <artifactId>maven-surefire-plugin</artifactId>
+            <configuration>
+              <useModulePath>false</useModulePath>
+              <argLine>-Duser.language=en -Duser.country=US -XX:+UnlockExperimentalVMOptions -XX:+EnableJVMCI --module-path=${project.build.directory}/graaljs-modules --add-modules=org.graalvm.polyglot --upgrade-module-path=${org.graalvm.compiler:compiler:jar} --add-exports=org.graalvm.truffle.compiler/com.oracle.truffle.compiler=jdk.graal.compiler --add-exports=org.graalvm.truffle.compiler/com.oracle.truffle.compiler.hotspot=jdk.graal.compiler --add-exports=org.graalvm.truffle.compiler/com.oracle.truffle.compiler.hotspot.libgraal=jdk.graal.compiler --add-exports=org.graalvm.word/org.graalvm.word.impl=jdk.graal.compiler</argLine>
+            </configuration>
+          </plugin>
+        </plugins>
+      </build>
+    </profile>
   </profiles>
 </project>

handlebars/src/main/java/com/github/jknack/handlebars/Handlebars.java

@@ -27,7 +27,6 @@
 
 import javax.script.Bindings;
 import javax.script.ScriptEngine;
-import javax.script.ScriptEngineManager;
 
 import org.slf4j.Logger;
 
@@ -38,6 +37,7 @@
 import com.github.jknack.handlebars.internal.Files;
 import com.github.jknack.handlebars.internal.FormatterChain;
 import com.github.jknack.handlebars.internal.HbsParserFactory;
+import com.github.jknack.handlebars.internal.ScriptEngineFactory;
 import com.github.jknack.handlebars.internal.Throwing;
 import com.github.jknack.handlebars.io.ClassPathTemplateLoader;
 import com.github.jknack.handlebars.io.CompositeTemplateLoader;
@@ -1442,19 +1442,21 @@ private static EscapingStrategy newEscapeChain(final EscapingStrategy[] chain) {
   }
 
   /**
-   * @return Nashorn engine.
+   * @return A JavaScript engine (GraalJS or Nashorn, whichever is available).
    */
   private ScriptEngine engine() {
     synchronized (this) {
       if (this.engine == null) {
 
-        this.engine = new ScriptEngineManager().getEngineByName("nashorn");
+        this.engine = ScriptEngineFactory.create();
 
-        Throwing.run(() -> {
-          //polyfill globalThis as it is used in handlebars 4.7.9 and is not supported by nashorn
-          engine.eval("var globalThis = this;");
-          engine.eval(Files.read(this.handlebarsJsFile, charset));
-        });
+        Throwing.run(
+            () -> {
+              if (ScriptEngineFactory.isNashorn(engine)) {
+                engine.eval("var globalThis = this;");
+              }
+              engine.eval(Files.read(this.handlebarsJsFile, charset));
+            });
       }
       return this.engine;
     }

handlebars/src/main/java/com/github/jknack/handlebars/helper/DefaultHelperRegistry.java

@@ -27,7 +27,6 @@
 import java.util.regex.Pattern;
 
 import javax.script.ScriptEngine;
-import javax.script.ScriptEngineManager;
 
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -37,6 +36,7 @@
 import com.github.jknack.handlebars.Helper;
 import com.github.jknack.handlebars.HelperRegistry;
 import com.github.jknack.handlebars.internal.Files;
+import com.github.jknack.handlebars.internal.ScriptEngineFactory;
 import com.github.jknack.handlebars.internal.Throwing;
 
 /**
@@ -175,7 +175,9 @@ public HelperRegistry registerHelpers(final String filename, final String source
     notNull(filename, "The filename is required.");
     notEmpty(source, "The source is required.");
     ScriptEngine engine = engine();
-    Throwing.run(() -> engine.eval(adaptES6Literals(source)));
+    String adaptedSource =
+        ScriptEngineFactory.isNashorn(engine) ? adaptES6Literals(source) : source;
+    Throwing.run(() -> engine.eval(adaptedSource));
     return this;
   }
 
@@ -276,12 +278,12 @@ public DefaultHelperRegistry setCharset(final Charset charset) {
   }
 
   /**
-   * @return Nashorn engine.
+   * @return A JavaScript engine (GraalJS or Nashorn, whichever is available).
    */
   private ScriptEngine engine() {
     synchronized (this) {
       if (this.engine == null) {
-        this.engine = new ScriptEngineManager().getEngineByName("nashorn");
+        this.engine = ScriptEngineFactory.create();
 
         this.engine.put("Handlebars_java", this);
 

handlebars/src/main/java/com/github/jknack/handlebars/internal/ScriptEngineFactory.java

@@ -0,0 +1,101 @@
+/*
+ * Handlebars.java: https://github.com/jknack/handlebars.java
+ * Apache License Version 2.0 http://www.apache.org/licenses/LICENSE-2.0
+ */
+package com.github.jknack.handlebars.internal;
+
+import javax.script.Bindings;
+import javax.script.ScriptContext;
+import javax.script.ScriptEngine;
+import javax.script.ScriptEngineManager;
+
+/**
+ * Factory for creating a JavaScript {@link ScriptEngine}. By default tries Nashorn first, then
+ * falls back to GraalJS. The engine can be forced via the {@code hbs.js_engine} system property.
+ */
+public final class ScriptEngineFactory {
+
+  private ScriptEngineFactory() {}
+
+  /**
+   * Create a JavaScript engine. If the system property {@code hbs.js_engine} is set, only that
+   * engine is tried. Otherwise tries Nashorn first, then GraalJS.
+   *
+   * @return a JavaScript ScriptEngine.
+   * @throws IllegalStateException if no JavaScript engine is available or the requested engine is
+   *     not found.
+   */
+  public static ScriptEngine create() {
+    String requested = System.getProperty("hbs.js_engine");
+    if (requested != null) {
+      return createRequested(requested);
+    }
+    return createDefault();
+  }
+
+  private static ScriptEngine createDefault() {
+    ScriptEngineManager manager = new ScriptEngineManager();
+
+    ScriptEngine engine = manager.getEngineByName("nashorn");
+    if (engine != null) {
+      return engine;
+    }
+
+    engine = manager.getEngineByName("graal.js");
+    if (engine != null) {
+      configureGraalJS(engine);
+      return engine;
+    }
+
+    throw new IllegalStateException(
+        "No JavaScript engine found. Add either GraalJS or Nashorn to the classpath.");
+  }
+
+  private static ScriptEngine createRequested(String name) {
+    ScriptEngineManager manager = new ScriptEngineManager();
+
+    switch (name) {
+      case "nashorn":
+        ScriptEngine nashorn = manager.getEngineByName("nashorn");
+        if (nashorn == null) {
+          throw new IllegalStateException(
+              "JavaScript engine 'nashorn' requested via hbs.js_engine but is not available."
+                  + " Add org.openjdk.nashorn:nashorn-core to the classpath.");
+        }
+        return nashorn;
+
+      case "graaljs":
+        ScriptEngine graaljs = manager.getEngineByName("graal.js");
+        if (graaljs == null) {
+          throw new IllegalStateException(
+              "JavaScript engine 'graaljs' requested via hbs.js_engine but is not available."
+                  + " Add org.graalvm.js:js-scriptengine to the classpath.");
+        }
+        configureGraalJS(graaljs);
+        return graaljs;
+
+      default:
+        throw new IllegalStateException(
+            "Unknown hbs.js_engine value: '"
+                + name
+                + "'. Supported values are 'nashorn' and 'graaljs'.");
+    }
+  }
+
+  private static void configureGraalJS(ScriptEngine engine) {
+    Bindings bindings = engine.getBindings(ScriptContext.ENGINE_SCOPE);
+    bindings.put("polyglot.js.allowAllAccess", true);
+    bindings.put("polyglot.js.nashorn-compat", true);
+    bindings.put("polyglot.js.ecmascript-version", "2022");
+  }
+
+  /**
+   * Check whether the given engine is Nashorn.
+   *
+   * @param engine the script engine.
+   * @return true if the engine is Nashorn.
+   */
+  public static boolean isNashorn(ScriptEngine engine) {
+    return engine.getFactory().getEngineName().toLowerCase().contains("nashorn");
+  }
+}

handlebars/src/test/java/com/github/jknack/handlebars/NashornTest.java

@@ -13,11 +13,11 @@
 import java.util.Map;
 
 import javax.script.ScriptEngine;
-import javax.script.ScriptEngineManager;
 import javax.script.SimpleBindings;
 
 import org.junit.jupiter.api.Test;
 
+import com.github.jknack.handlebars.internal.ScriptEngineFactory;
 import com.github.jknack.handlebars.js.JavaScriptHelperTest;
 
 public class NashornTest {
@@ -45,13 +45,13 @@ public String getName() {
   @Test
   public void bootstrap() throws Exception {
     Handlebars hbs = new Handlebars();
-    ScriptEngine nashorn = new ScriptEngineManager().getEngineByName("nashorn");
+    ScriptEngine engine = ScriptEngineFactory.create();
     SimpleBindings bindings = new SimpleBindings();
     bindings.put("Handlebars_java", hbs);
-    nashorn.eval(
+    engine.eval(
         new FileReader(Paths.get("src/main/resources/helpers.nashorn.js").toFile()), bindings);
 
-    nashorn.eval(
+    engine.eval(
         new FileReader(
             Paths.get("src/test/resources/com/github/jknack/handlebars/js/helpers.js").toFile()),
         bindings);