Add theme variants demo and test helpers.

flow-components-parent/flow-component-demo-helpers/src/main/java/com/vaadin/flow/demo/ComponentDemoTest.java

@@ -15,12 +15,23 @@
  */
 package com.vaadin.flow.demo;
 
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.List;
+import java.util.function.BiConsumer;
+import java.util.function.Function;
+import java.util.function.Supplier;
+
+import org.junit.Assert;
 import org.junit.Before;
 import org.openqa.selenium.By;
 import org.openqa.selenium.WebElement;
 
 import com.vaadin.flow.testutil.ChromeBrowserTest;
 
+import static com.vaadin.flow.demo.DemoView.COMPONENT_WITH_VARIANTS_ID;
+import static com.vaadin.flow.demo.DemoView.VARIANT_TOGGLE_BUTTONS_DIV_ID;
+
 /**
  * Base class for the integration tests of component demos.
  *
@@ -43,4 +54,85 @@ public void openDemoPageAndCheckForErrors() {
         layout = findElement(By.className("demo-view"));
         checkLogsForErrors();
     }
+
+    /**
+     * Verifies variants functionality for the current layout.
+     * 
+     * The test will fail if a specific variant demo is not added first with
+     * {@link DemoView#addVariantsDemo(Supplier, BiConsumer, BiConsumer, Function, Enum[])}
+     * method.
+     */
+    protected void verifyThemeVariantsBeingToggled() {
+        List<WebElement> toggleThemeButtons = layout
+                .findElement(By.id(VARIANT_TOGGLE_BUTTONS_DIV_ID))
+                .findElements(By.tagName("button"));
+        Assert.assertFalse(
+                "Expected at least one toggle theme button in 'buttonDiv', but got none",
+                toggleThemeButtons.isEmpty());
+        toggleThemeButtons.forEach(button -> toggleVariantAndCheck(
+                layout.findElement(By.id(COMPONENT_WITH_VARIANTS_ID)), button));
+    }
+
+    private void toggleVariantAndCheck(WebElement component,
+            WebElement button) {
+        List<String> initialButtonThemes = getComponentThemes(component);
+        String initialButtonText = button.getText();
+
+        button.click();
+        verifyThemeIsToggled(getComponentThemes(component), button.getText(),
+                initialButtonThemes, initialButtonText);
+
+        button.click();
+        Assert.assertEquals(
+                "After two toggle variants button clicks, button text should be the same as before testing",
+                button.getText(), initialButtonText);
+
+        List<String> currentThemes = getComponentThemes(component);
+        String assertionMessage = "After two toggle variants button clicks, component 'theme' attribute should contain the same value as before testing";
+        Assert.assertEquals(assertionMessage, currentThemes.size(),
+                initialButtonThemes.size());
+        currentThemes.forEach(currentTheme -> Assert.assertTrue(
+                assertionMessage + String.format(
+                        " but theme variant '%s' is missing", currentTheme),
+                initialButtonThemes.contains(currentTheme)));
+
+    }
+
+    private void verifyThemeIsToggled(List<String> updatedThemes,
+            String updatedButtonText, List<String> previousThemes,
+            String previousButtonText) {
+        Assert.assertNotEquals("Button should change its text after toggling",
+                previousButtonText, updatedButtonText);
+
+        boolean shouldAddTheme = previousButtonText.startsWith("Add");
+        if (shouldAddTheme) {
+            Assert.assertTrue(
+                    "When a theme variant got added, toggle button text should start with 'Remove' word",
+                    updatedButtonText.startsWith("Remove"));
+            Assert.assertEquals(
+                    "When a theme variant got added, component 'theme' attribute should contain one more variant that before",
+                    previousThemes.size() + 1, updatedThemes.size());
+            Assert.assertTrue(
+                    "When a theme variant got added, component 'theme' attribute should contain all previous theme variants",
+                    updatedThemes.containsAll(previousThemes));
+        } else {
+            Assert.assertTrue(
+                    "When a theme variant got removed, toggle button text should start with 'Add' word",
+                    updatedButtonText.startsWith("Add"));
+            Assert.assertEquals(
+                    "When a theme variant got removed, component 'theme' attribute should contain one less variant than before",
+                    previousThemes.size() - 1, updatedThemes.size());
+            Assert.assertTrue(
+                    "When a theme variant got removed, previous theme variants should contain all theme variants from component 'theme' attribute",
+                    previousThemes.containsAll(updatedThemes));
+        }
+    }
+
+    private List<String> getComponentThemes(WebElement component) {
+        String themeAttributeValue = component.getAttribute("theme");
+        if (themeAttributeValue == null || themeAttributeValue.isEmpty()) {
+            return Collections.emptyList();
+        }
+        return Arrays.asList(themeAttributeValue.split(" "));
+    }
 }

flow-components-parent/flow-component-demo-helpers/src/main/java/com/vaadin/flow/demo/DemoView.java

@@ -19,16 +19,21 @@
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.function.BiConsumer;
+import java.util.function.Function;
+import java.util.function.Supplier;
 
 import com.vaadin.flow.component.AttachEvent;
 import com.vaadin.flow.component.Component;
 import com.vaadin.flow.component.HasComponents;
 import com.vaadin.flow.component.HasStyle;
+import com.vaadin.flow.component.HasTheme;
 import com.vaadin.flow.component.Tag;
 import com.vaadin.flow.component.dependency.JavaScript;
 import com.vaadin.flow.component.dependency.StyleSheet;
 import com.vaadin.flow.component.html.Div;
 import com.vaadin.flow.component.html.H3;
+import com.vaadin.flow.component.html.NativeButton;
 import com.vaadin.flow.router.BeforeEvent;
 import com.vaadin.flow.router.HasUrlParameter;
 import com.vaadin.flow.router.OptionalParameter;
@@ -49,12 +54,14 @@
 @JavaScript("src/script/prism.js")
 public abstract class DemoView extends Component
         implements HasComponents, HasUrlParameter<String>, HasStyle {
+    static final String VARIANT_TOGGLE_BUTTONS_DIV_ID = "variantToggleButtonsDiv";
+    static final String COMPONENT_WITH_VARIANTS_ID = "componentWithVariantsDemo";
 
-    private DemoNavigationBar navBar = new DemoNavigationBar();
-    private Div container = new Div();
+    private final DemoNavigationBar navBar = new DemoNavigationBar();
+    private final Div container = new Div();
 
-    private Map<String, Div> tabComponents = new HashMap<>();
-    private Map<String, List<SourceCodeExample>> sourceCodeExamples = new HashMap<>();
+    private final Map<String, Div> tabComponents = new HashMap<>();
+    private final Map<String, List<SourceCodeExample>> sourceCodeExamples = new HashMap<>();
 
     protected DemoView() {
         Route annotation = getClass().getAnnotation(Route.class);
@@ -211,4 +218,71 @@ public void setParameter(BeforeEvent event,
             @OptionalParameter String parameter) {
         showTab(parameter == null ? "" : parameter);
     }
+
+    /**
+     * Adds a demo that shows how the component looks like with specific
+     * variants applied.
+     *
+     * @param componentSupplier
+     *            a method that creates the component to which variants will be
+     *            applied to
+     * @param addVariant
+     *            a function that adds the new variant to the component
+     * @param removeVariant
+     *            a function that removes the variant from the component
+     * @param variantToThemeName
+     *            function that converts variant to an html theme name
+     * @param variants
+     *            list of variants to show in the demos
+     * @param <T>
+     *            variants' type
+     * @param <C>
+     *            component's type
+     */
+    protected <T extends Enum<?>, C extends Component & HasTheme> void addVariantsDemo(
+            Supplier<C> componentSupplier, BiConsumer<C, T> addVariant,
+            BiConsumer<C, T> removeVariant,
+            Function<T, String> variantToThemeName, T... variants) {
+
+        C component = componentSupplier.get();
+        component.setId(COMPONENT_WITH_VARIANTS_ID);
+
+        Div message = new Div();
+        message.setText(
+                "Toggle a variant to see how the component's appearance will change!");
+
+        Div variantsToggles = new Div();
+        variantsToggles.setId(VARIANT_TOGGLE_BUTTONS_DIV_ID);
+        for (T variant : variants) {
+            if (variant.name().startsWith("LUMO_")) {
+                String variantName = variantToThemeName.apply(variant);
+                variantsToggles
+                        .add(new NativeButton(
+                                getButtonText(variantName,
+                                        component.getThemeNames()
+                                                .contains(variantName)),
+                                event -> {
+                                    boolean variantPresent = component
+                                            .getThemeNames()
+                                            .contains(variantName);
+                                    if (variantPresent) {
+                                        removeVariant.accept(component,
+                                                variant);
+                                    } else {
+                                        addVariant.accept(component, variant);
+                                    }
+                                    event.getSource().setText(getButtonText(
+                                            variantName, !variantPresent));
+                                }));
+
+            }
+        }
+        addCard("Theme variants usage", message, component, variantsToggles);
+    }
+
+    private String getButtonText(String variantName, boolean variantPresent) {
+        return String.format(
+                variantPresent ? "Remove '%s' variant" : "Add '%s' variant",
+                variantName);
+    }
 }