feat: add signal bind methods to details component

vaadin-details-flow-parent/vaadin-details-flow/src/main/java/com/vaadin/flow/component/details/Details.java

@@ -35,6 +35,7 @@
 import com.vaadin.flow.component.shared.HasThemeVariant;
 import com.vaadin.flow.component.shared.HasTooltip;
 import com.vaadin.flow.component.shared.SlotUtils;
+import com.vaadin.flow.function.SerializableConsumer;
 import com.vaadin.flow.function.SerializableFunction;
 import com.vaadin.flow.shared.Registration;
 import com.vaadin.flow.signals.Signal;
@@ -441,6 +442,28 @@ public void setOpened(boolean opened) {
         doSetOpened(opened);
     }
 
+    /**
+     * Binds the opened state to the given signal. The binding is two-way:
+     * signal changes push to the DOM property, and client-side property changes
+     * invoke the write callback.
+     * <p>
+     * While a signal is bound, any attempt to set the opened state manually
+     * throws {@link com.vaadin.flow.signals.BindingActiveException}.
+     *
+     * @param signal
+     *            the signal to bind, not {@code null}
+     * @param writeCallback
+     *            the callback to propagate value changes back, or {@code null}
+     *            for a read-only binding
+     * @since 25.1
+     */
+    public void bindOpened(Signal<Boolean> signal,
+            SerializableConsumer<Boolean> writeCallback) {
+        Objects.requireNonNull(signal, "Signal cannot be null");
+        getElement().bindProperty("opened",
+                signal.map(v -> v == null ? Boolean.FALSE : v), writeCallback);
+    }
+
     public static class OpenedChangeEvent extends ComponentEvent<Details> {
         private final boolean opened;
 

vaadin-details-flow-parent/vaadin-details-flow/src/test/java/com/vaadin/flow/component/details/DetailsOpenedSignalTest.java

@@ -0,0 +1,104 @@
+/*
+ * Copyright 2000-2026 Vaadin Ltd.
+ *
+ * Licensed 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 com.vaadin.flow.component.details;
+
+import org.junit.After;
+import org.junit.Assert;
+import org.junit.Before;
+import org.junit.Test;
+
+import com.vaadin.flow.component.UI;
+import com.vaadin.flow.signals.BindingActiveException;
+import com.vaadin.flow.signals.local.ValueSignal;
+import com.vaadin.tests.AbstractSignalsUnitTest;
+
+public class DetailsOpenedSignalTest extends AbstractSignalsUnitTest {
+
+    private Details details;
+    private ValueSignal<Boolean> signal;
+
+    @Before
+    public void setup() {
+        details = new Details();
+        signal = new ValueSignal<>(false);
+    }
+
+    @After
+    public void tearDown() {
+        if (details != null && details.isAttached()) {
+            details.removeFromParent();
+        }
+    }
+
+    @Test
+    public void bindOpened_signalBound_propertySync() {
+        details.bindOpened(signal, signal::set);
+        UI.getCurrent().add(details);
+
+        Assert.assertFalse(details.isOpened());
+
+        signal.set(true);
+        Assert.assertTrue(details.isOpened());
+
+        signal.set(false);
+        Assert.assertFalse(details.isOpened());
+    }
+
+    @Test
+    public void bindOpened_notAttached_noEffect() {
+        details.bindOpened(signal, signal::set);
+
+        boolean initial = details.isOpened();
+        signal.set(true);
+        Assert.assertEquals(initial, details.isOpened());
+    }
+
+    @Test
+    public void bindOpened_detachAndReattach() {
+        details.bindOpened(signal, signal::set);
+        UI.getCurrent().add(details);
+
+        signal.set(true);
+        Assert.assertTrue(details.isOpened());
+
+        details.removeFromParent();
+        signal.set(false);
+        Assert.assertTrue(details.isOpened());
+
+        UI.getCurrent().add(details);
+        Assert.assertFalse(details.isOpened());
+    }
+
+    @Test(expected = BindingActiveException.class)
+    public void bindOpened_setWhileBound_throws() {
+        details.bindOpened(signal, signal::set);
+        UI.getCurrent().add(details);
+
+        details.setOpened(true);
+    }
+
+    @Test(expected = BindingActiveException.class)
+    public void bindOpened_doubleBind_throws() {
+        details.bindOpened(signal, signal::set);
+        var other = new ValueSignal<>(true);
+        details.bindOpened(other, other::set);
+    }
+
+    @Test(expected = NullPointerException.class)
+    public void bindOpened_nullSignal_throwsNPE() {
+        details.bindOpened(null, null);
+    }
+}