feat!: Implement HasPlaceholder

flow-html-components/src/main/java/com/vaadin/flow/component/html/Input.java

@@ -15,11 +15,10 @@
  */
 package com.vaadin.flow.component.html;
 
-import java.util.Optional;
-
 import com.vaadin.flow.component.AbstractSinglePropertyField;
 import com.vaadin.flow.component.Focusable;
 import com.vaadin.flow.component.HasAriaLabel;
+import com.vaadin.flow.component.HasPlaceholder;
 import com.vaadin.flow.component.HasSize;
 import com.vaadin.flow.component.HasStyle;
 import com.vaadin.flow.component.PropertyDescriptor;
@@ -35,11 +34,12 @@
  * @since 1.0
  */
 @Tag(Tag.INPUT)
-public class Input extends AbstractSinglePropertyField<Input, String> implements
-        Focusable<Input>, HasSize, HasStyle, HasValueChangeMode, HasAriaLabel {
+public class Input extends AbstractSinglePropertyField<Input, String>
+        implements Focusable<Input>, HasSize, HasStyle, HasValueChangeMode,
+        HasAriaLabel, HasPlaceholder {
 
-    private static final PropertyDescriptor<String, Optional<String>> placeholderDescriptor = PropertyDescriptors
-            .optionalAttributeWithDefault("placeholder", "");
+    private static final PropertyDescriptor<String, String> placeholderDescriptor = PropertyDescriptors
+            .attributeWithDefault("placeholder", "");
 
     private static final PropertyDescriptor<String, String> typeDescriptor = PropertyDescriptors
             .attributeWithDefault("type", "text");
@@ -68,26 +68,11 @@ public Input(ValueChangeMode valueChangeMode) {
         setValueChangeMode(valueChangeMode);
     }
 
-    /**
-     * Sets the placeholder text that is shown if the input is empty.
-     *
-     * @param placeholder
-     *            the placeholder text to set, or <code>null</code> to remove
-     *            the placeholder
-     */
     public void setPlaceholder(String placeholder) {
         set(placeholderDescriptor, placeholder);
     }
 
-    /**
-     * Gets the placeholder text.
-     *
-     * @see #setPlaceholder(String)
-     *
-     * @return an optional placeholder, or an empty optional if no placeholder
-     *         has been set
-     */
-    public Optional<String> getPlaceholder() {
+    public String getPlaceholder() {
         return get(placeholderDescriptor);
     }
 

flow-html-components/src/test/java/com/vaadin/flow/component/html/InputTest.java

@@ -35,7 +35,7 @@ protected void addProperties() {
         addStringProperty("type", "text");
         // Object.class because of generics
         addProperty("value", Object.class, "", "foo", false, false);
-        addOptionalStringProperty("placeholder");
+        addStringProperty("placeholder", "");
     }
 
     @Test

flow-server/src/main/java/com/vaadin/flow/component/HasPlaceholder.java

@@ -0,0 +1,51 @@
+/*
+ * Copyright 2000-2023 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;
+
+/**
+ * A component which supports a placeholder.
+ * <p>
+ * A placeholder is a text that should be displayed in the input element, when
+ * the user has not entered a value.
+ * <p>
+ * The default implementations sets the <code>placeholder</code> property for
+ * this element. Override all methods in this interface if the placeholder
+ * should be set in some other way.
+ */
+public interface HasPlaceholder extends HasElement {
+    /**
+     * Sets the placeholder text that should be displayed in the input element,
+     * when the user has not entered a value
+     *
+     * @param placeholder
+     *            the placeholder text, may be null.
+     */
+    default void setPlaceholder(String placeholder) {
+        getElement().setProperty("placeholder",
+                placeholder == null ? "" : placeholder);
+    }
+
+    /**
+     * The placeholder text that should be displayed in the input element, when
+     * the user has not entered a value
+     *
+     * @return the {@code placeholder} property from the web component. May be
+     *         null if not yet set.
+     */
+    default String getPlaceholder() {
+        return getElement().getProperty("placeholder");
+    }
+}

flow-server/src/test/java/com/vaadin/flow/component/HasPlaceholderTest.java

@@ -0,0 +1,60 @@
+/*
+ * Copyright 2000-2023 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;
+
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNull;
+
+public class HasPlaceholderTest {
+
+    @Tag(Tag.DIV)
+    private static class TestComponent extends Component
+            implements HasPlaceholder {
+
+    }
+
+    @Test
+    public void withoutPlaceholderComponent_getPlaceholderReturnsNull() {
+        TestComponent component = new TestComponent();
+
+        assertNull(component.getPlaceholder());
+    }
+
+    @Test
+    public void withNullPlaceholder_getPlaceholderReturnsEmptyString() {
+        TestComponent component = new TestComponent();
+        component.setPlaceholder(null);
+        assertEquals("", component.getPlaceholder());
+    }
+
+    @Test
+    public void withEmptyPlaceholder_getPlaceholderReturnsEmptyString() {
+        TestComponent component = new TestComponent();
+        component.setPlaceholder("");
+        assertEquals("", component.getPlaceholder());
+    }
+
+    @Test
+    public void setPlaceholder() {
+        TestComponent component = new TestComponent();
+        component.setPlaceholder("test Placeholder");
+
+        assertEquals("test Placeholder", component.getPlaceholder());
+    }
+
+}