fix: allow metadata service export when application deployer is PENDING

dubbo-config/dubbo-config-api/src/main/java/org/apache/dubbo/config/deploy/DefaultApplicationDeployer.java

@@ -1296,7 +1296,11 @@ private void onInitialize() {
     }
 
     private void doExportMetadataService() {
-        if (!isStarting() && !isStarted() && !isCompletion()) {
+        // Skip only when the application is shutting down or has failed.
+        // PENDING is allowed so that programmatic ServiceConfig.export() invoked
+        // before the application has been started can still trigger the
+        // metadata service export (see issue #14859).
+        if (isStopping() || isStopped() || isFailed()) {
             return;
         }
         for (DeployListener<ApplicationModel> listener : listeners) {

dubbo-config/dubbo-config-api/src/test/java/org/apache/dubbo/config/deploy/DefaultApplicationDeployerTest.java

@@ -16,10 +16,16 @@
  */
 package org.apache.dubbo.config.deploy;
 
+import org.apache.dubbo.common.deploy.ApplicationDeployListener;
 import org.apache.dubbo.common.utils.Assert;
 import org.apache.dubbo.config.MetricsConfig;
 import org.apache.dubbo.metrics.utils.MetricsSupportUtil;
+import org.apache.dubbo.rpc.model.ApplicationModel;
+import org.apache.dubbo.rpc.model.FrameworkModel;
 
+import java.util.concurrent.atomic.AtomicInteger;
+
+import org.junit.jupiter.api.Assertions;
 import org.junit.jupiter.api.Test;
 
 import static org.apache.dubbo.common.constants.MetricsConstants.PROTOCOL_PROMETHEUS;
@@ -40,4 +46,65 @@ void isImportPrometheus() {
                 PROTOCOL_PROMETHEUS.equals(metricsConfig.getProtocol()) && !MetricsSupportUtil.isSupportPrometheus();
         Assert.assertTrue(!importPrometheus, " should return false");
     }
+
+    /**
+     * See <a href="https://github.com/apache/dubbo/issues/14859">#14859</a>.
+     * <p>
+     * Programmatic {@code ServiceConfig.export()} may invoke
+     * {@code ApplicationDeployer.exportMetadataService()} while the application
+     * deployer is still in the {@code PENDING} state (e.g. when the user wires
+     * Dubbo via XML without any {@code <dubbo:service/>} entry and then exports
+     * services manually). The metadata service must still be exported in that
+     * case, otherwise instance-level registration is silently skipped.
+     */
+    @Test
+    void exportMetadataServiceShouldFireListenersWhenDeployerIsPending() {
+        FrameworkModel frameworkModel = new FrameworkModel();
+        try {
+            ApplicationModel applicationModel = frameworkModel.newApplication();
+            DefaultApplicationDeployer deployer =
+                    (DefaultApplicationDeployer) DefaultApplicationDeployer.get(applicationModel);
+
+            AtomicInteger moduleStartedInvocations = new AtomicInteger();
+            deployer.addDeployListener(new ApplicationDeployListener() {
+                @Override
+                public void onInitialize(ApplicationModel scopeModel) {}
+
+                @Override
+                public void onStarting(ApplicationModel scopeModel) {}
+
+                @Override
+                public void onStarted(ApplicationModel scopeModel) {}
+
+                @Override
+                public void onCompletion(ApplicationModel scopeModel) {}
+
+                @Override
+                public void onStopping(ApplicationModel scopeModel) {}
+
+                @Override
+                public void onStopped(ApplicationModel scopeModel) {}
+
+                @Override
+                public void onFailure(ApplicationModel scopeModel, Throwable cause) {}
+
+                @Override
+                public void onModuleStarted(ApplicationModel scopeModel) {
+                    moduleStartedInvocations.incrementAndGet();
+                }
+            });
+
+            // Sanity: the deployer is in PENDING state until start() is called.
+            Assertions.assertTrue(deployer.isPending());
+
+            deployer.exportMetadataService();
+
+            Assertions.assertEquals(
+                    1,
+                    moduleStartedInvocations.get(),
+                    "ApplicationDeployListener.onModuleStarted should be invoked even when the deployer is in PENDING state");
+        } finally {
+            frameworkModel.destroy();
+        }
+    }
 }