feat: add setSubtitle method for setting Card subtitle as a string (#8204)

Co-authored-by: Artur <artur@vaadin.com>
Co-authored-by: Claude <noreply@anthropic.com>

Author: 3 people

vaadin-card-flow-parent/vaadin-card-flow-integration-tests/src/main/java/com/vaadin/flow/component/card/tests/CardPage.java

@@ -30,7 +30,7 @@ public CardPage() {
         Card card = new Card();
 
         card.setTitle(new Span("Title"));
-        card.setSubtitle(new Span("Subtitle"));
+        card.setSubtitle("Subtitle");
         card.setMedia(
                 new Image("https://vaadin.com/images/vaadin-logo.svg", ""));
         card.setHeaderPrefix(new Span("Header prefix"));

vaadin-card-flow-parent/vaadin-card-flow/pom.xml

@@ -11,6 +11,11 @@
     <name>Vaadin Card</name>
     <description>Vaadin Card</description>
     <dependencies>
+        <dependency>
+            <groupId>com.vaadin</groupId>
+            <artifactId>flow-html-components</artifactId>
+            <version>${project.version}</version>
+        </dependency>
         <dependency>
             <groupId>com.vaadin</groupId>
             <artifactId>flow-test-generic</artifactId>

vaadin-card-flow-parent/vaadin-card-flow/src/main/java/com/vaadin/flow/component/card/Card.java

@@ -31,6 +31,7 @@
 import com.vaadin.flow.component.Tag;
 import com.vaadin.flow.component.dependency.JsModule;
 import com.vaadin.flow.component.dependency.NpmPackage;
+import com.vaadin.flow.component.html.Span;
 import com.vaadin.flow.component.shared.HasThemeVariant;
 import com.vaadin.flow.component.shared.SlotUtils;
 import com.vaadin.flow.dom.Element;
@@ -185,6 +186,23 @@ public void setSubtitle(Component subtitle) {
         SlotUtils.setSlot(this, SUBTITLE_SLOT_NAME, subtitle);
     }
 
+    /**
+     * Sets the card's subtitle. If a {@link #setHeader(Component) header
+     * component} is set, the subtitle will not be displayed.
+     * <p>
+     * Passing {@code null} removes the current subtitle from the card.
+     *
+     * @param subtitle
+     *            the subtitle, or {@code null} to remove
+     */
+    public void setSubtitle(String subtitle) {
+        if (subtitle == null) {
+            setSubtitle((Component) null);
+        } else {
+            setSubtitle(new Span(subtitle));
+        }
+    }
+
     /**
      * Gets the current subtitle component.
      *

vaadin-card-flow-parent/vaadin-card-flow/src/test/java/com/vaadin/flow/component/card/CardTest.java

@@ -139,6 +139,41 @@ public void setSubtitle_slotAttributeSet() {
         setSlotContent_slotAttributeIsSet(Card::setSubtitle, "subtitle");
     }
 
+    @Test
+    public void setStringSubtitle_subtitleIsSet() {
+        var subtitle = "Some Subtitle";
+        card.setSubtitle(subtitle);
+        Assert.assertNotNull(card.getSubtitle());
+        Assert.assertTrue(card.getSubtitle() instanceof Span);
+        Assert.assertEquals(subtitle, ((Span) card.getSubtitle()).getText());
+    }
+
+    @Test
+    public void setStringSubtitle_setNullStringSubtitle_subtitleCleared() {
+        card.setSubtitle("Some Subtitle");
+        card.setSubtitle((String) null);
+        Assert.assertNull(card.getSubtitle());
+    }
+
+    @Test
+    public void setStringSubtitle_setComponentSubtitle_stringSubtitleIsReplaced() {
+        card.setSubtitle("Some Subtitle");
+        var newSubtitle = new Div("Other Subtitle");
+        card.setSubtitle(newSubtitle);
+        Assert.assertEquals(newSubtitle, card.getSubtitle());
+    }
+
+    @Test
+    public void setComponentSubtitle_setStringSubtitle_componentSubtitleIsReplaced() {
+        var componentSubtitle = new Div("Component Subtitle");
+        card.setSubtitle(componentSubtitle);
+        var stringSubtitle = "String Subtitle";
+        card.setSubtitle(stringSubtitle);
+        Assert.assertTrue(card.getSubtitle() instanceof Span);
+        Assert.assertEquals(stringSubtitle,
+                ((Span) card.getSubtitle()).getText());
+    }
+
     @Test
     public void mediaNullByDefault() {
         Assert.assertNull(card.getMedia());