feat: add theme API to MessageListItem

vaadin-messages-flow-parent/vaadin-messages-flow-integration-tests/src/main/java/com/vaadin/flow/component/messages/tests/MessageListPage.java

@@ -51,6 +51,8 @@ public MessageListPage() {
         addButton("setUserImage", () -> foo.setUserImage("/test2.jpg"));
         addButton("setAbbreviation", () -> foo.setUserAbbreviation("CD"));
         addButton("setUserColorIndex", () -> foo.setUserColorIndex(2));
+        addButton("addThemeNames", () -> foo.addThemeNames("foo", "bar"));
+        addButton("removeThemeNames", () -> foo.removeThemeNames("foo", "bar"));
 
         addButton("setItems", () -> messageList
                 .setItems(new MessageListItem(null, null, "sender3")));

vaadin-messages-flow-parent/vaadin-messages-flow-integration-tests/src/test/java/com/vaadin/flow/component/messages/tests/MessageListIT.java

@@ -93,6 +93,14 @@ public void updateItemPropertiesAfterRendering_messagesUpdated() {
         clickElementWithJs("setUserColorIndex");
         Assert.assertEquals("Unexpected userColorIndex prop", 2,
                 msg.getUserColorIndex());
+
+        clickElementWithJs("addThemeNames");
+        Assert.assertEquals("Unexpected theme prop after adding theme names",
+                "foo bar", msg.getTheme());
+
+        clickElementWithJs("removeThemeNames");
+        Assert.assertEquals("Unexpected theme prop after removing theme names",
+                null, msg.getTheme());
     }
 
     @Test

vaadin-messages-flow-parent/vaadin-messages-flow/src/main/java/com/vaadin/flow/component/messages/MessageListItem.java

@@ -18,9 +18,14 @@
 import java.io.Serializable;
 import java.net.URI;
 import java.time.Instant;
+import java.util.Arrays;
 import java.util.Collection;
+import java.util.LinkedHashSet;
 import java.util.Optional;
+import java.util.Set;
+import java.util.stream.Collectors;
 
+import com.fasterxml.jackson.annotation.JsonGetter;
 import com.fasterxml.jackson.annotation.JsonIgnore;
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.fasterxml.jackson.databind.annotation.JsonSerialize;
@@ -58,6 +63,8 @@ public class MessageListItem implements Serializable {
     private Command pendingHandle;
     private AbstractStreamResource imageResource;
 
+    private Set<String> themeNames = new LinkedHashSet<>();
+
     /**
      * Creates an empty message list item. Use the setter methods to configure
      * what will be displayed in the message.
@@ -282,6 +289,52 @@ public void setUserColorIndex(Integer userColorIndex) {
         propsChanged();
     }
 
+    /**
+     * Adds one or more theme names to this message. Multiple theme names can be
+     * specified by using multiple parameters.
+     *
+     * @param themeNames
+     *            the theme name or theme names to be added to the message
+     */
+    public void addThemeNames(String... themeNames) {
+        this.themeNames.addAll(Arrays.asList(themeNames));
+        propsChanged();
+    }
+
+    /**
+     * Removes one or more theme names from this message. Multiple theme names
+     * can be specified by using multiple parameters.
+     *
+     * @param themeNames
+     *            the theme name or theme names to be removed from the message
+     */
+    public void removeThemeNames(String... themeNames) {
+        this.themeNames.removeAll(Arrays.asList(themeNames));
+        propsChanged();
+    }
+
+    /**
+     * Checks if the message has the given theme name.
+     *
+     * @param themeName
+     *            the theme name to check for
+     * @return <code>true</code> if the message has the given theme name,
+     *         <code>false</code> otherwise
+     */
+    public boolean hasThemeName(String themeName) {
+        return themeNames.contains(themeName);
+    }
+
+    // Used only for Jackson serialization
+    @JsonGetter
+    private String getTheme() {
+        if (themeNames.isEmpty()) {
+            return null;
+        } else {
+            return themeNames.stream().collect(Collectors.joining(" "));
+        }
+    }
+
     /**
      * Gets the image resource of the message sender's avatar.
      *

vaadin-messages-flow-parent/vaadin-messages-flow/src/test/java/com/vaadin/flow/component/messages/tests/MessageListTest.java

@@ -29,8 +29,12 @@
 import com.vaadin.flow.component.UI;
 import com.vaadin.flow.component.messages.MessageList;
 import com.vaadin.flow.component.messages.MessageListItem;
+import com.vaadin.flow.internal.JsonUtils;
 import com.vaadin.flow.server.StreamResource;
 
+import elemental.json.JsonType;
+import elemental.json.JsonValue;
+
 public class MessageListTest {
 
     private MessageList messageList;
@@ -91,4 +95,51 @@ public void setImageAsUrl_streamResourceBecomesNull() {
         item1.setUserImage("foo/bar");
         Assert.assertNull(item1.getUserImageResource());
     }
+
+    @Test
+    public void addThemeNames_serialize_separatedBySpaces() {
+        item1.addThemeNames("foo", "bar");
+        item1.addThemeNames("baz");
+        Assert.assertEquals("foo bar baz", getSerializedThemeProperty(item1));
+    }
+
+    @Test
+    public void addThemeNames_serialize_noDuplicates() {
+        item1.addThemeNames("foo", "foo");
+        Assert.assertEquals("foo", getSerializedThemeProperty(item1));
+    }
+
+    @Test
+    public void removeThemeNames_serialize_themeNamesRemoved() {
+        item1.addThemeNames("foo", "bar", "baz");
+        item1.removeThemeNames("foo", "bar", "qux");
+        Assert.assertEquals("baz", getSerializedThemeProperty(item1));
+    }
+
+    @Test
+    public void clearThemeNames_serialize_nullProperty() {
+        item1.addThemeNames("foo");
+        item1.removeThemeNames("foo");
+        Assert.assertNull(getSerializedThemeProperty(item1));
+    }
+
+    @Test
+    public void hasThemeName_falseForNonExistingThemeName() {
+        Assert.assertFalse(item1.hasThemeName("foo"));
+    }
+
+    @Test
+    public void hasThemeName_trueForExistingThemeName() {
+        item1.addThemeNames("foo");
+        Assert.assertTrue(item1.hasThemeName("foo"));
+    }
+
+    private String getSerializedThemeProperty(MessageListItem item) {
+        JsonValue theme = JsonUtils.beanToJson(item).get("theme");
+        if (theme.getType() == JsonType.NULL) {
+            return null;
+        } else {
+            return theme.asString();
+        }
+    }
 }

vaadin-messages-flow-parent/vaadin-messages-testbench/src/main/java/com/vaadin/flow/component/messages/testbench/MessageElement.java

@@ -82,4 +82,13 @@ public int getUserColorIndex() {
         return getPropertyInteger("userColorIndex");
     }
 
+    /**
+     * Gets the {@code theme} attribute of this element.
+     *
+     * @return the {@code theme} attribute
+     */
+    public String getTheme() {
+        return getAttribute("theme");
+    }
+
 }