feat: add i18n error message support for ComboBox, MultiSelectComboBox

vaadin-combo-box-flow-parent/vaadin-combo-box-flow-integration-tests/src/main/java/com/vaadin/flow/component/combobox/test/validation/ComboBoxBasicValidationPage.java

@@ -10,9 +10,13 @@
 public class ComboBoxBasicValidationPage
         extends AbstractValidationPage<ComboBox<String>> {
     public static final String REQUIRED_BUTTON = "required-button";
+    public static final String REQUIRED_ERROR_MESSAGE = "Field is required";
     public static final String ENABLE_CUSTOM_VALUE_BUTTON = "enable-custom-value-button";
 
     public ComboBoxBasicValidationPage() {
+        testField.setI18n(new ComboBox.ComboBoxI18n()
+                .setRequiredErrorMessage(REQUIRED_ERROR_MESSAGE));
+
         add(createButton(REQUIRED_BUTTON, "Enable required", event -> {
             testField.setRequired(true);
         }));

vaadin-combo-box-flow-parent/vaadin-combo-box-flow-integration-tests/src/main/java/com/vaadin/flow/component/combobox/test/validation/MultiSelectComboBoxBasicValidationPage.java

@@ -1,6 +1,7 @@
 package com.vaadin.flow.component.combobox.test.validation;
 
 import com.vaadin.flow.component.combobox.MultiSelectComboBox;
+import com.vaadin.flow.component.combobox.MultiSelectComboBoxI18n;
 import com.vaadin.flow.router.Route;
 import com.vaadin.tests.validation.AbstractValidationPage;
 
@@ -10,9 +11,13 @@
 public class MultiSelectComboBoxBasicValidationPage
         extends AbstractValidationPage<MultiSelectComboBox<String>> {
     public static final String REQUIRED_BUTTON = "required-button";
+    public static final String REQUIRED_ERROR_MESSAGE = "Field is required";
     public static final String ENABLE_CUSTOM_VALUE_BUTTON = "enable-custom-value-button";
 
     public MultiSelectComboBoxBasicValidationPage() {
+        testField.setI18n(new MultiSelectComboBoxI18n()
+                .setRequiredErrorMessage(REQUIRED_ERROR_MESSAGE));
+
         add(createButton(REQUIRED_BUTTON, "Enable required", event -> {
             testField.setRequired(true);
         }));

vaadin-combo-box-flow-parent/vaadin-combo-box-flow-integration-tests/src/test/java/com/vaadin/flow/component/combobox/test/validation/ComboBoxBasicValidationIT.java

@@ -8,6 +8,7 @@
 
 import static com.vaadin.flow.component.combobox.test.validation.ComboBoxBasicValidationPage.ENABLE_CUSTOM_VALUE_BUTTON;
 import static com.vaadin.flow.component.combobox.test.validation.ComboBoxBasicValidationPage.REQUIRED_BUTTON;
+import static com.vaadin.flow.component.combobox.test.validation.ComboBoxBasicValidationPage.REQUIRED_ERROR_MESSAGE;
 
 @TestPath("vaadin-combo-box/validation/basic")
 public class ComboBoxBasicValidationIT
@@ -17,6 +18,7 @@ public class ComboBoxBasicValidationIT
     public void fieldIsInitiallyValid() {
         assertClientValid();
         assertServerValid();
+        assertErrorMessage(null);
     }
 
     @Test
@@ -25,6 +27,7 @@ public void triggerBlur_assertValidity() {
         assertValidationCount(0);
         assertServerValid();
         assertClientValid();
+        assertErrorMessage(null);
     }
 
     @Test
@@ -35,6 +38,7 @@ public void required_triggerBlur_assertValidity() {
         assertValidationCount(0);
         assertServerValid();
         assertClientValid();
+        assertErrorMessage(null);
     }
 
     @Test
@@ -45,11 +49,13 @@ public void required_changeValue_assertValidity() {
         assertValidationCount(1);
         assertServerValid();
         assertClientValid();
+        assertErrorMessage("");
 
         testField.clear();
         assertValidationCount(1);
         assertServerInvalid();
         assertClientInvalid();
+        assertErrorMessage(REQUIRED_ERROR_MESSAGE);
     }
 
     @Test
@@ -60,6 +66,7 @@ public void required_enterCustomValue_assertValidity() {
         assertValidationCount(0);
         assertServerValid();
         assertClientValid();
+        assertErrorMessage(null);
     }
 
     @Test
@@ -71,6 +78,7 @@ public void required_customValuesAllowed_enterCustomValue_assertValidity() {
         assertValidationCount(1);
         assertServerValid();
         assertClientValid();
+        assertErrorMessage("");
     }
 
     @Test

vaadin-combo-box-flow-parent/vaadin-combo-box-flow-integration-tests/src/test/java/com/vaadin/flow/component/combobox/test/validation/MultiSelectComboBoxBasicValidationIT.java

@@ -8,6 +8,7 @@
 
 import static com.vaadin.flow.component.combobox.test.validation.MultiSelectComboBoxBasicValidationPage.ENABLE_CUSTOM_VALUE_BUTTON;
 import static com.vaadin.flow.component.combobox.test.validation.MultiSelectComboBoxBasicValidationPage.REQUIRED_BUTTON;
+import static com.vaadin.flow.component.combobox.test.validation.MultiSelectComboBoxBasicValidationPage.REQUIRED_ERROR_MESSAGE;
 
 @TestPath("vaadin-multi-select-combo-box/validation/basic")
 public class MultiSelectComboBoxBasicValidationIT
@@ -17,6 +18,7 @@ public class MultiSelectComboBoxBasicValidationIT
     public void fieldIsInitiallyValid() {
         assertClientValid();
         assertServerValid();
+        assertErrorMessage(null);
     }
 
     @Test
@@ -25,6 +27,7 @@ public void triggerBlur_assertValidity() {
         assertValidationCount(0);
         assertServerValid();
         assertClientValid();
+        assertErrorMessage(null);
     }
 
     @Test
@@ -35,6 +38,7 @@ public void required_triggerBlur_assertValidity() {
         assertValidationCount(0);
         assertServerValid();
         assertClientValid();
+        assertErrorMessage(null);
     }
 
     @Test
@@ -45,11 +49,13 @@ public void required_changeValue_assertValidity() {
         assertValidationCount(1);
         assertServerValid();
         assertClientValid();
+        assertErrorMessage("");
 
         testField.deselectAll();
         assertValidationCount(1);
         assertServerInvalid();
         assertClientInvalid();
+        assertErrorMessage(REQUIRED_ERROR_MESSAGE);
     }
 
     @Test
@@ -60,6 +66,7 @@ public void required_enterCustomValue_assertValidity() {
         assertValidationCount(0);
         assertServerValid();
         assertClientValid();
+        assertErrorMessage(null);
     }
 
     @Test
@@ -71,11 +78,13 @@ public void required_customValuesAllowed_enterCustomValue_assertValidity() {
         assertValidationCount(1);
         assertServerValid();
         assertClientValid();
+        assertErrorMessage("");
 
         testField.deselectAll();
         assertValidationCount(1);
         assertServerInvalid();
         assertClientInvalid();
+        assertErrorMessage(REQUIRED_ERROR_MESSAGE);
     }
 
     @Test

vaadin-combo-box-flow-parent/vaadin-combo-box-flow/src/main/java/com/vaadin/flow/component/combobox/ComboBox.java

@@ -18,6 +18,8 @@
 import java.io.Serializable;
 import java.util.Collection;
 import java.util.Objects;
+import java.util.Optional;
+import java.util.function.Function;
 import java.util.stream.Stream;
 
 import com.vaadin.flow.component.HasSize;
@@ -353,4 +355,66 @@ public void setOverlayWidth(float width, Unit unit) {
         Objects.requireNonNull(unit, "Unit can not be null");
         setOverlayWidth(HasSize.getCssSize(width, unit));
     }
+
+    /**
+     * Gets the internationalization object previously set for this component.
+     * <p>
+     * NOTE: Updating the instance that is returned from this method will not
+     * update the component if not set again using
+     * {@link #setI18n(ComboBoxI18n)}
+     *
+     * @return the i18n object or {@code null} if no i18n object has been set
+     */
+    public ComboBoxI18n getI18n() {
+        return (ComboBoxI18n) super.getI18n();
+    }
+
+    /**
+     * Sets the internationalization object for this component.
+     *
+     * @param i18n
+     *            the i18n object, not {@code null}
+     */
+    public void setI18n(ComboBoxI18n i18n) {
+        super.setI18n(i18n);
+    }
+
+    /**
+     * The internationalization properties for {@link ComboBox}.
+     */
+    public static class ComboBoxI18n implements ComboBoxBaseI18n {
+
+        private String requiredErrorMessage;
+
+        /**
+         * Gets the error message displayed when the field is required but
+         * empty.
+         *
+         * @return the error message or {@code null} if not set
+         * @see ComboBox#isRequiredIndicatorVisible()
+         * @see ComboBox#setRequiredIndicatorVisible(boolean)
+         */
+        public String getRequiredErrorMessage() {
+            return requiredErrorMessage;
+        }
+
+        /**
+         * Sets the error message to display when the field is required but
+         * empty.
+         * <p>
+         * Note, custom error messages set with
+         * {@link ComboBox#setErrorMessage(String)} take priority over i18n
+         * error messages.
+         *
+         * @param errorMessage
+         *            the error message or {@code null} to clear it
+         * @return this instance for method chaining
+         * @see ComboBox#isRequiredIndicatorVisible()
+         * @see ComboBox#setRequiredIndicatorVisible(boolean)
+         */
+        public ComboBoxI18n setRequiredErrorMessage(String errorMessage) {
+            requiredErrorMessage = errorMessage;
+            return this;
+        }
+    }
 }

vaadin-combo-box-flow-parent/vaadin-combo-box-flow/src/main/java/com/vaadin/flow/component/combobox/ComboBoxBase.java

@@ -44,6 +44,7 @@
 import com.vaadin.flow.component.shared.InputField;
 import com.vaadin.flow.component.shared.ValidationUtil;
 import com.vaadin.flow.data.binder.HasValidator;
+import com.vaadin.flow.data.binder.ValidationResult;
 import com.vaadin.flow.data.provider.BackEndDataProvider;
 import com.vaadin.flow.data.provider.CallbackDataProvider;
 import com.vaadin.flow.data.provider.CompositeDataGenerator;
@@ -69,6 +70,7 @@
 import java.util.Locale;
 import java.util.Objects;
 import java.util.Optional;
+import java.util.function.Function;
 
 /**
  * Provides base functionality for combo box related components, such as
@@ -123,8 +125,13 @@ public void remove() {
     private final ComboBoxDataController<TItem> dataController;
     private int customValueListenersCount;
 
+    private ComboBoxBaseI18n i18n;
+
     private boolean manualValidationEnabled = false;
 
+    private String customErrorMessage;
+    private String constraintErrorMessage;
+
     /**
      * Constructs a new ComboBoxBase instance
      *
@@ -184,6 +191,45 @@ public Locale get() {
         addValueChangeListener(e -> validate());
     }
 
+    /**
+     * Sets an error message to display for all constraint violations.
+     * <p>
+     * This error message takes priority over i18n error messages when both are
+     * set.
+     *
+     * @param errorMessage
+     *            the error message to set, or {@code null} to clear
+     *
+     */
+    @Override
+    public void setErrorMessage(String errorMessage) {
+        customErrorMessage = errorMessage;
+        updateErrorMessage();
+    }
+
+    /**
+     * Gets the error message displayed for all constraint violations.
+     *
+     * @return the error message
+     */
+    @Override
+    public String getErrorMessage() {
+        return customErrorMessage;
+    }
+
+    private void setConstraintErrorMessage(String errorMessage) {
+        constraintErrorMessage = errorMessage;
+        updateErrorMessage();
+    }
+
+    private void updateErrorMessage() {
+        String errorMessage = constraintErrorMessage;
+        if (customErrorMessage != null && !customErrorMessage.isEmpty()) {
+            errorMessage = customErrorMessage;
+        }
+        getElement().setProperty("errorMessage", errorMessage);
+    }
+
     /**
      * Whether the component should automatically receive focus when the page
      * loads.
@@ -1190,13 +1236,29 @@ public void setManualValidation(boolean enabled) {
         this.manualValidationEnabled = enabled;
     }
 
+    /**
+     * Validates the current value against the constraints and sets the
+     * {@code invalid} property and the {@code errorMessage} property based on
+     * the result. If a custom error message is provided with
+     * {@link #setErrorMessage(String)}, it is used. Otherwise, the error
+     * message defined in the i18n object is used.
+     * <p>
+     * The method does nothing if the manual validation mode is enabled.
+     */
     protected void validate() {
-        if (!this.manualValidationEnabled) {
-            boolean isInvalid = ValidationUtil.validateRequiredConstraint("",
-                    isRequiredIndicatorVisible(), getValue(), getEmptyValue())
-                    .isError();
+        if (this.manualValidationEnabled) {
+            return;
+        }
 
-            setInvalid(isInvalid);
+        ValidationResult result = ValidationUtil.validateRequiredConstraint(
+                getI18nErrorMessage(ComboBoxBaseI18n::getRequiredErrorMessage),
+                isRequiredIndicatorVisible(), getValue(), getEmptyValue());
+        if (result.isError()) {
+            setInvalid(true);
+            setConstraintErrorMessage(result.getErrorMessage());
+        } else {
+            setInvalid(false);
+            setConstraintErrorMessage("");
         }
     }
 
@@ -1223,4 +1285,33 @@ public String getDetail() {
             return detail;
         }
     }
+
+    /**
+     * Gets the internationalization object previously set for this component.
+     * <p>
+     * NOTE: Updating the instance that is returned from this method will not
+     * update the component if not set again using
+     * {@link #setI18n(ComboBoxBaseI18n)}
+     *
+     * @return the i18n object or {@code null} if no i18n object has been set
+     */
+    protected ComboBoxBaseI18n getI18n() {
+        return i18n;
+    }
+
+    /**
+     * Sets the internationalization object for this component.
+     *
+     * @param i18n
+     *            the i18n object, not {@code null}
+     */
+    protected void setI18n(ComboBoxBaseI18n i18n) {
+        this.i18n = Objects.requireNonNull(i18n,
+                "The i18n properties object should not be null");
+    }
+
+    private String getI18nErrorMessage(
+            Function<ComboBoxBaseI18n, String> getter) {
+        return Optional.ofNullable(i18n).map(getter).orElse("");
+    }
 }