GROOVY-9381: Support async/await like ES7

src/antlr/GroovyLexer.g4

@@ -406,7 +406,9 @@ BuiltInPrimitiveType
     ;
 
 ABSTRACT      : 'abstract';
+ASYNC         : 'async';
 ASSERT        : 'assert';
+AWAIT         : 'await';
 
 fragment
 BOOLEAN       : 'boolean';

src/antlr/GroovyParser.g4

@@ -130,6 +130,7 @@ modifier
     :   classOrInterfaceModifier
     |   m=(   NATIVE
           |   SYNCHRONIZED
+          |   ASYNC
           |   TRANSIENT
           |   VOLATILE
           |   DEF
@@ -776,6 +777,12 @@ expression
     // must come before postfixExpression to resolve the ambiguities between casting and call on parentheses expression, e.g. (int)(1 / 2)
     :   castParExpression castOperandExpression                                             #castExprAlt
 
+    // async expression
+    |   ASYNC nls closureOrLambdaExpression                                                 #asyncExprAlt
+
+    // await expression
+    |   AWAIT nls expression                                                                #awaitExprAlt
+
     // qualified names, array expressions, method invocation, post inc/dec
     |   postfixExpression                                                                   #postfixExprAlt
 
@@ -1226,6 +1233,8 @@ identifier
     :   Identifier
     |   CapitalizedIdentifier
     |   AS
+    |   ASYNC
+    |   AWAIT
     |   IN
     |   PERMITS
     |   RECORD
@@ -1243,7 +1252,9 @@ builtInType
 keywords
     :   ABSTRACT
     |   AS
+    |   ASYNC
     |   ASSERT
+    |   AWAIT
     |   BREAK
     |   CASE
     |   CATCH

src/main/java/groovy/transform/Async.java

@@ -0,0 +1,39 @@
+/*
+ *  Licensed to the Apache Software Foundation (ASF) under one
+ *  or more contributor license agreements.  See the NOTICE file
+ *  distributed with this work for additional information
+ *  regarding copyright ownership.  The ASF licenses this file
+ *  to you under the Apache License, Version 2.0 (the
+ *  "License"); you may not use this file except in compliance
+ *  with the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing,
+ *  software distributed under the License is distributed on an
+ *  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ *  KIND, either express or implied.  See the License for the
+ *  specific language governing permissions and limitations
+ *  under the License.
+ */
+package groovy.transform;
+
+import org.codehaus.groovy.transform.GroovyASTTransformationClass;
+
+import java.lang.annotation.Documented;
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+/**
+ * Annotation used to mark async methods, closures and lambda expressions.
+ *
+ * @since 6.0.0
+ */
+@Documented
+@Retention(RetentionPolicy.SOURCE)
+@Target({ElementType.METHOD, ElementType.LOCAL_VARIABLE, ElementType.FIELD})
+@GroovyASTTransformationClass({"org.codehaus.groovy.transform.AsyncASTTransformation"})
+public @interface Async {
+}

src/main/java/groovy/util/concurrent/async/AsyncHelper.java

@@ -0,0 +1,116 @@
+/*
+ *  Licensed to the Apache Software Foundation (ASF) under one
+ *  or more contributor license agreements.  See the NOTICE file
+ *  distributed with this work for additional information
+ *  regarding copyright ownership.  The ASF licenses this file
+ *  to you under the Apache License, Version 2.0 (the
+ *  "License"); you may not use this file except in compliance
+ *  with the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing,
+ *  software distributed under the License is distributed on an
+ *  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ *  KIND, either express or implied.  See the License for the
+ *  specific language governing permissions and limitations
+ *  under the License.
+ */
+package groovy.util.concurrent.async;
+
+import org.apache.groovy.util.SystemUtil;
+
+import java.lang.invoke.MethodHandle;
+import java.lang.invoke.MethodHandles;
+import java.lang.invoke.MethodType;
+import java.util.concurrent.Executor;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.function.Supplier;
+
+/**
+ * Helper class for async/await operations
+ *
+ * @since 6.0.0
+ */
+public class AsyncHelper {
+    private static final int PARALLELISM = SystemUtil.getIntegerSafe("groovy.async.parallelism", Runtime.getRuntime().availableProcessors() + 1);
+    private static final Executor DEFAULT_EXECUTOR;
+    private static int seq;
+
+    static {
+        Executor tmpExecutor;
+        try {
+            MethodHandle mh = MethodHandles.lookup().findStatic(
+                Executors.class,
+                "newVirtualThreadPerTaskExecutor",
+                MethodType.methodType(ExecutorService.class)
+            );
+            tmpExecutor = (Executor) mh.invoke();
+        } catch (Throwable throwable) {
+            // Fallback to default thread pool if virtual threads are not available
+            tmpExecutor = Executors.newFixedThreadPool(PARALLELISM, r -> {
+                Thread t = new Thread(r);
+                t.setName("async-thread-" + seq++);
+                return t;
+            });
+        }
+        DEFAULT_EXECUTOR = tmpExecutor;
+    }
+
+    /**
+     * Submits a supplier for asynchronous execution using the default executor
+     *
+     * @param supplier the supplier
+     * @param <T>      the result type
+     * @return the promise
+     */
+    public static <T> Promise<T> async(Supplier<T> supplier) {
+        return SimplePromise.of(supplier, DEFAULT_EXECUTOR);
+    }
+
+    /**
+     * Submits a supplier for asynchronous execution using the provided executor
+     *
+     * @param supplier the supplier
+     * @param executor the executor
+     * @param <T>      the result type
+     * @return the promise
+     */
+    public static <T> Promise<T> async(Supplier<T> supplier, Executor executor) {
+        return SimplePromise.of(supplier, executor);
+    }
+
+    /**
+     * Awaits the result of an awaitable
+     *
+     * @param awaitable the awaitable
+     * @param <T>       the result type
+     * @return the result
+     */
+    public static <T> T await(Awaitable<T> awaitable) {
+        if (null == awaitable) return null;
+
+        return awaitable.await();
+    }
+
+    /**
+     * Awaits the result of an object implementing Awaitable
+     *
+     * @param obj the object
+     * @param <T> the result type
+     * @return the result
+     * @throws IllegalArgumentException if the object does not implement Awaitable
+     */
+    @SuppressWarnings("unchecked")
+    public static <T> T await(Object obj) {
+        if (null == obj) return null;
+
+        if (!(obj instanceof Awaitable)) {
+            throw new IllegalArgumentException("type " + obj.getClass().getName() + " does not implement " + Awaitable.class.getName());
+        }
+        return await((Awaitable<T>) obj);
+    }
+
+    private AsyncHelper() {}
+}

src/main/java/groovy/util/concurrent/async/AwaitException.java

@@ -0,0 +1,44 @@
+/*
+ *  Licensed to the Apache Software Foundation (ASF) under one
+ *  or more contributor license agreements.  See the NOTICE file
+ *  distributed with this work for additional information
+ *  regarding copyright ownership.  The ASF licenses this file
+ *  to you under the Apache License, Version 2.0 (the
+ *  "License"); you may not use this file except in compliance
+ *  with the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing,
+ *  software distributed under the License is distributed on an
+ *  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ *  KIND, either express or implied.  See the License for the
+ *  specific language governing permissions and limitations
+ *  under the License.
+ */
+package groovy.util.concurrent.async;
+
+/**
+ * Exception thrown when attempting to wait for the result of a promise
+ * that aborted by throwing an exception. This exception can be
+ * inspected using the {@link #getCause()} method.
+ *
+ * @see Promise
+ * @since 6.0.0
+ */
+public class AwaitException extends RuntimeException {
+    public AwaitException() {
+    }
+
+    public AwaitException(String message) {
+        super(message);
+    }
+
+    public AwaitException(Throwable cause) {
+        super(cause);
+    }
+
+    public AwaitException(String message, Throwable cause) {
+        super(message, cause);
+    }
+}

src/main/java/groovy/util/concurrent/async/Awaitable.java

@@ -0,0 +1,35 @@
+/*
+ *  Licensed to the Apache Software Foundation (ASF) under one
+ *  or more contributor license agreements.  See the NOTICE file
+ *  distributed with this work for additional information
+ *  regarding copyright ownership.  The ASF licenses this file
+ *  to you under the Apache License, Version 2.0 (the
+ *  "License"); you may not use this file except in compliance
+ *  with the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing,
+ *  software distributed under the License is distributed on an
+ *  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ *  KIND, either express or implied.  See the License for the
+ *  specific language governing permissions and limitations
+ *  under the License.
+ */
+package groovy.util.concurrent.async;
+
+/**
+ * Represents a result of an asynchronous computation
+ *
+ * @since 6.0.0
+ */
+public interface Awaitable<T> {
+    /**
+     * Waits if necessary for the computation to complete, and then retrieves its
+     * result.
+     *
+     * @return the computed result
+     * @throws AwaitException if the computation was cancelled or completed exceptionally
+     */
+    T await();
+}