Binder.validate() no longer fails with "bean level validators have been configured but no bean is currently set" when in buffered mode

flow-data/src/main/java/com/vaadin/flow/data/binder/Binder.java

@@ -2586,16 +2586,11 @@ public BinderValidationStatus<BEAN> validate() {
      *
      */
     protected BinderValidationStatus<BEAN> validate(boolean fireEvent) {
-        if (getBean() == null && !validators.isEmpty()) {
-            throw new IllegalStateException("Cannot validate binder: "
-                    + "bean level validators have been configured "
-                    + "but no bean is currently set");
-        }
         List<BindingValidationStatus<?>> bindingStatuses = validateBindings();
 
         BinderValidationStatus<BEAN> validationStatus;
-        if (validators.isEmpty() || bindingStatuses.stream()
-                .anyMatch(BindingValidationStatus::isError)) {
+        if (validators.isEmpty() || getBean() == null || bindingStatuses
+                .stream().anyMatch(BindingValidationStatus::isError)) {
             validationStatus = new BinderValidationStatus<>(this,
                     bindingStatuses, Collections.emptyList());
         } else {

flow-data/src/main/java/com/vaadin/flow/data/binder/Validator.java

@@ -78,6 +78,18 @@ static <T> Validator<T> alwaysPass() {
         return (value, context) -> ValidationResult.ok();
     }
 
+    /**
+     * Returns a validator that fails on any value.
+     *
+     * @param <T>
+     *            the value type
+     * @return an always-failing validator
+     */
+    static <T> Validator<T> alwaysFail(String errorMessage) {
+        Objects.requireNonNull(errorMessage);
+        return (value, context) -> ValidationResult.error(errorMessage);
+    }
+
     /**
      * Builds a validator out of a conditional function and an error message. If
      * the function returns true, the validator returns {@code Result.ok()}; if

flow-data/src/test/java/com/vaadin/flow/data/binder/BinderConverterValidatorTest.java

@@ -469,22 +469,27 @@ public void save_fieldValidationErrors() throws ValidationException {
         }
     }
 
-    @Test(expected = ValidationException.class)
-    public void save_beanValidationErrors() throws ValidationException {
+    @Test
+    public void save_beanValidationErrors() {
         Binder<Person> binder = new Binder<>();
         binder.forField(nameField).withValidator(new NotEmptyValidator<>("a"))
                 .bind(Person::getFirstName, Person::setFirstName);
 
-        binder.withValidator(Validator.from(person -> false, "b"));
+        binder.withValidator(Validator.alwaysFail("b"));
 
         Person person = new Person();
         nameField.setValue("foo");
         try {
             binder.writeBean(person);
-        } finally {
-            // Bean should have been updated for item validation but reverted
-            assertNull(person.getFirstName());
+            Assert.fail("Validation should have failed but it passed instead");
+        } catch (ValidationException ex) {
+            // writeBean() should run bean validations
+            Assert.assertEquals(1, ex.getBeanValidationErrors().size());
+            // field validations pass
+            Assert.assertEquals(0, ex.getFieldValidationErrors().size());
         }
+        // Bean should have been updated for item validation but reverted
+        assertNull(person.getFirstName());
     }
 
     @Test

flow-data/src/test/java/com/vaadin/flow/data/binder/BinderTest.java

@@ -1147,14 +1147,14 @@ public void isValidTest_unbound_binder() {
         Assert.assertTrue(binder.isValid());
     }
 
-    @Test(expected = IllegalStateException.class)
-    public void isValidTest_unbound_binder_throws_with_bean_level_validation() {
+    @Test
+    public void isValidTest_unbound_binder_passes_with_bean_level_validation() {
         binder.forField(nameField).bind(Person::getFirstName,
                 Person::setFirstName);
         binder.withValidator(Validator.from(
                 person -> !person.getFirstName().equals("fail bean validation"),
                 ""));
-        binder.isValid();
+        Assert.assertTrue(binder.isValid());
     }
 
     @Test
@@ -1433,20 +1433,22 @@ public void beanvalidation_initially_broken_bean() {
         Assert.assertFalse(binder.validate().isOk());
     }
 
-    @Test(expected = IllegalStateException.class)
-    public void beanvalidation_isValid_throws_with_readBean() {
+    @Test
+    public void beanvalidation_isValid_passes_with_readBean() {
         TestTextField lastNameField = new TestTextField();
         setBeanValidationFirstNameNotEqualsLastName(nameField, lastNameField);
+        binder.withValidator(Validator.alwaysFail("fail"));
 
         binder.readBean(item);
 
         Assert.assertTrue(binder.isValid());
     }
 
-    @Test(expected = IllegalStateException.class)
-    public void beanvalidation_validate_throws_with_readBean() {
+    @Test
+    public void beanvalidation_validate_passes_with_readBean() {
         TestTextField lastNameField = new TestTextField();
         setBeanValidationFirstNameNotEqualsLastName(nameField, lastNameField);
+        binder.withValidator(Validator.alwaysFail("fail"));
 
         binder.readBean(item);