✨ feat: Enhance V8 await mode

* Add `V8AwaitMode.RunNoWait`
* Fix unexpected behavior of `V8AwaitMode.RunOnce`

Author: caoccao

cpp/jni/javet_enums.h

@@ -28,8 +28,9 @@ namespace Javet {
 
         namespace V8AwaitMode {
             enum V8AwaitMode {
-                RunOnce = 0,
-                RunTillNoMoreTasks = 1,
+                RunNoWait = 2,
+                RunOnce = 1,
+                RunTillNoMoreTasks = 0,
             };
         };
 

cpp/jni/javet_v8_runtime.cpp

@@ -97,6 +97,19 @@ namespace Javet {
     bool V8Runtime::Await(const Javet::Enums::V8AwaitMode::V8AwaitMode awaitMode) noexcept {
         bool hasMoreTasks = false;
 #ifdef ENABLE_NODE
+        uv_run_mode uvRunMode;
+        switch (awaitMode)
+        {
+        case Javet::Enums::V8AwaitMode::V8AwaitMode::RunOnce:
+            uvRunMode = UV_RUN_ONCE;
+            break;
+        case Javet::Enums::V8AwaitMode::V8AwaitMode::RunNoWait:
+            uvRunMode = UV_RUN_NOWAIT;
+            break;
+        default:
+            uvRunMode = UV_RUN_DEFAULT;
+            break;
+        }
         do {
             {
                 // Reduce the locking granularity so that Node.js can respond to requests from other threads.
@@ -105,12 +118,12 @@ namespace Javet {
                 V8HandleScope v8HandleScope(v8Isolate);
                 auto v8Context = GetV8LocalContext();
                 auto v8ContextScope = GetV8ContextScope(v8Context);
-                uv_run(&uvLoop, UV_RUN_NOWAIT);
+                uv_run(&uvLoop, uvRunMode);
                 // DrainTasks is thread-safe.
                 v8PlatformPointer->DrainTasks(v8Isolate);
             }
             hasMoreTasks = uv_loop_alive(&uvLoop);
-            if (hasMoreTasks) {
+            if (uvRunMode == UV_RUN_DEFAULT && hasMoreTasks) {
                 // Sleep a while to give CPU cycles to other threads.
                 std::this_thread::sleep_for(oneMillisecond);
             }
@@ -124,7 +137,7 @@ namespace Javet {
                 node::EmitProcessBeforeExit(nodeEnvironment.get());
                 hasMoreTasks = uv_loop_alive(&uvLoop);
             }
-        } while (awaitMode == Javet::Enums::V8AwaitMode::RunTillNoMoreTasks && hasMoreTasks);
+        } while (uvRunMode == UV_RUN_DEFAULT && hasMoreTasks);
 #else
         // It has to be v8::platform::MessageLoopBehavior::kDoNotWait, otherwise it blockes;
         v8::platform::PumpMessageLoop(v8PlatformPointer, v8Isolate);

docs/release_notes/release_notes_3_1.rst

@@ -2,6 +2,12 @@
 Release Notes 3.1.x
 ===================
 
+3.1.2 V8 v12.5
+--------------
+
+* Added ``V8AwaitMode.RunNoWait``
+* Fixed unexpected behavior of ``V8AwaitMode.RunOnce``
+
 3.1.1 V8 v12.4
 --------------
 

src/main/java/com/caoccao/javet/enums/V8AwaitMode.java

@@ -23,19 +23,27 @@
  */
 public enum V8AwaitMode {
     /**
-     * Run once tells Javet to drain the tasks once and return.
+     * RunNoWait tells Javet to trigger the task queue execution but do not wait.
+     * It only works in Node.js mode.
+     *
+     * @since 3.1.2
+     */
+    RunNoWait(2),
+    /**
+     * RunOnce tells Javet to drain the tasks once and return.
      * It only works in Node.js mode.
      *
      * @since 2.0.4
      */
-    RunOnce(0),
+    RunOnce(1),
     /**
-     * Run till no more tasks tells Javet to keep waiting till there are no more tasks.
+     * RunTillNoMoreTasks tells Javet to keep waiting till there are no more tasks.
+     * This is the default mode.
      * It only works in Node.js mode.
      *
      * @since 2.0.4
      */
-    RunTillNoMoreTasks(1);
+    RunTillNoMoreTasks(0);
 
     private final int id;
 

src/test/java/com/caoccao/javet/interop/TestNodeRuntime.java

@@ -18,8 +18,10 @@
 
 import com.caoccao.javet.BaseTestJavet;
 import com.caoccao.javet.enums.JSRuntimeType;
+import com.caoccao.javet.enums.V8AwaitMode;
 import com.caoccao.javet.exceptions.JavetError;
 import com.caoccao.javet.exceptions.JavetException;
+import com.caoccao.javet.interop.converters.JavetProxyConverter;
 import com.caoccao.javet.interop.options.NodeRuntimeOptions;
 import com.caoccao.javet.node.modules.NodeModuleAny;
 import com.caoccao.javet.node.modules.NodeModuleProcess;
@@ -35,6 +37,7 @@
 import java.nio.file.Path;
 import java.nio.file.StandardOpenOption;
 import java.text.MessageFormat;
+import java.util.concurrent.atomic.AtomicInteger;
 
 import static org.junit.jupiter.api.Assertions.*;
 
@@ -82,6 +85,81 @@ protected void internalTest(String fileName, String expectedJsonString) throws J
         }
     }
 
+    @Test
+    public void testAwaitRunNoWait() {
+        try {
+            nodeRuntime.setConverter(new JavetProxyConverter());
+            AtomicInteger counter = new AtomicInteger();
+            nodeRuntime.getGlobalObject().set("counter", counter);
+            nodeRuntime.getExecutor("let timeoutIDs = [];" +
+                    "function a() {\n" +
+                    "  counter.incrementAndGet();\n" +
+                    "  if (counter.get() < 10) {\n" +
+                    "    timeoutIDs.push(setTimeout(a, 1000));\n" +
+                    "  }\n" +
+                    "};\n" +
+                    "a();").executeVoid();
+            assertTrue(nodeRuntime.await(V8AwaitMode.RunNoWait));
+            nodeRuntime.getExecutor("timeoutIDs.forEach(id => clearTimeout(id));").executeVoid();
+            assertEquals(1, counter.get());
+            nodeRuntime.getGlobalObject().delete("counter");
+        } catch (Throwable t) {
+            fail(t);
+        } finally {
+            nodeRuntime.lowMemoryNotification();
+        }
+    }
+
+    @Test
+    public void testAwaitRunOnce() {
+        try {
+            nodeRuntime.setConverter(new JavetProxyConverter());
+            AtomicInteger counter = new AtomicInteger();
+            nodeRuntime.getGlobalObject().set("counter", counter);
+            nodeRuntime.getExecutor("let timeoutIDs = [];" +
+                    "function a() {\n" +
+                    "  counter.incrementAndGet();\n" +
+                    "  if (counter.get() < 10) {\n" +
+                    "    timeoutIDs.push(setTimeout(a, 0));\n" +
+                    "  }\n" +
+                    "};\n" +
+                    "a();").executeVoid();
+            while (counter.get() < 2) {
+                assertTrue(nodeRuntime.await(V8AwaitMode.RunOnce));
+            }
+            nodeRuntime.getExecutor("timeoutIDs.forEach(id => clearTimeout(id));").executeVoid();
+            assertEquals(2, counter.get());
+            nodeRuntime.getGlobalObject().delete("counter");
+        } catch (Throwable t) {
+            fail(t);
+        } finally {
+            nodeRuntime.lowMemoryNotification();
+        }
+    }
+
+    @Test
+    public void testAwaitRunTillNoMoreTasks() {
+        try {
+            nodeRuntime.setConverter(new JavetProxyConverter());
+            AtomicInteger counter = new AtomicInteger();
+            nodeRuntime.getGlobalObject().set("counter", counter);
+            nodeRuntime.getExecutor("function a() {\n" +
+                    "  counter.incrementAndGet();\n" +
+                    "  if (counter.get() < 10) {\n" +
+                    "    setTimeout(a, 0);\n" +
+                    "  }\n" +
+                    "};\n" +
+                    "a();").executeVoid();
+            assertFalse(nodeRuntime.await(V8AwaitMode.RunTillNoMoreTasks));
+            assertEquals(10, counter.get());
+            nodeRuntime.getGlobalObject().delete("counter");
+        } catch (Throwable t) {
+            fail(t);
+        } finally {
+            nodeRuntime.lowMemoryNotification();
+        }
+    }
+
     @Test
     public void testConsoleArguments() throws JavetException {
         NodeRuntimeOptions runtimeOptions = new NodeRuntimeOptions();