Add isValid to Binder (#8274)

* Add isValid to Binder

isValid enables you to check the current validation
status of a given Binder, without firing events or invoking
handlers.

This patch also clarifies the javadocs of StatusChangeEvents'
hasValidationErrors.

* Throw in Binder.isValid if no bean is set and bean validators exist

* Add test cases to BinderTest

2 files changed, 79 insertions, 2 deletions

diff --git a/server/src/test/java/com/vaadin/data/BinderBookOfVaadinTest.java b/server/src/test/java/com/vaadin/data/BinderBookOfVaadinTest.java
index 59ca890740..f36a357617 100644
--- a/server/src/test/java/com/vaadin/data/BinderBookOfVaadinTest.java
+++ b/server/src/test/java/com/vaadin/data/BinderBookOfVaadinTest.java
@@ -724,7 +724,7 @@ public class BinderBookOfVaadinTest {
         AtomicBoolean eventIsFired = new AtomicBoolean(false);
 
         binder.addStatusChangeListener(event -> {
-            boolean isValid = !event.hasValidationErrors();
+            boolean isValid = event.getBinder().isValid();
             boolean hasChanges = event.getBinder().hasChanges();
             eventIsFired.set(true);
 
@@ -782,7 +782,7 @@ public class BinderBookOfVaadinTest {
         AtomicBoolean eventIsFired = new AtomicBoolean(false);
 
         binder.addStatusChangeListener(event -> {
-            boolean isValid = !event.hasValidationErrors();
+            boolean isValid = event.getBinder().isValid();
             boolean hasChanges = event.getBinder().hasChanges();
             eventIsFired.set(true);
 
@@ -824,6 +824,31 @@ public class BinderBookOfVaadinTest {
         verifyEventIsFired(eventIsFired);
     }
 
+    @Test
+    public void statusChangeListener_multipleRequiredFields() {
+        Button saveButton = new Button();
+
+        binder.addStatusChangeListener(event -> {
+            boolean isValid = event.getBinder().isValid();
+            boolean hasChanges = event.getBinder().hasChanges();
+
+            saveButton.setEnabled(hasChanges && isValid);
+        });
+
+        binder.forField(field).asRequired("").bind(BookPerson::getLastName,
+                BookPerson::setLastName);
+        binder.forField(emailField).asRequired("").bind(BookPerson::getEmail,
+                BookPerson::setEmail);
+
+        Assert.assertFalse(saveButton.isEnabled());
+        field.setValue("not empty");
+        Assert.assertFalse(saveButton.isEnabled());
+        emailField.setValue("not empty");
+        Assert.assertTrue(saveButton.isEnabled());
+        field.clear();
+        Assert.assertFalse(saveButton.isEnabled());
+    }
+
     private void verifyEventIsFired(AtomicBoolean flag) {
         Assert.assertTrue(flag.get());
         flag.set(false);
diff --git a/server/src/test/java/com/vaadin/data/BinderTest.java b/server/src/test/java/com/vaadin/data/BinderTest.java
index e07aee9632..8dc4c76c3b 100644
--- a/server/src/test/java/com/vaadin/data/BinderTest.java
+++ b/server/src/test/java/com/vaadin/data/BinderTest.java
@@ -494,4 +494,56 @@ public class BinderTest extends BinderTestBase<Binder<Person>, Person> {
         Assert.assertFalse(ageField.isReadOnly());
     }
 
+    @Test
+    public void isValidTest_bound_binder() {
+        binder.forField(nameField)
+                .withValidator(
+                        Validator.from(
+                                name -> !name.equals("fail field validation"),
+                                ""))
+                .bind(Person::getFirstName, Person::setFirstName);
+
+        binder.withValidator(
+                Validator.from(person -> !person.getFirstName()
+                        .equals("fail bean validation"), ""));
+
+        binder.setBean(item);
+
+        Assert.assertTrue(binder.isValid());
+
+        nameField.setValue("fail field validation");
+        Assert.assertFalse(binder.isValid());
+
+        nameField.setValue("");
+        Assert.assertTrue(binder.isValid());
+
+        nameField.setValue("fail bean validation");
+        Assert.assertFalse(binder.isValid());
+    }
+
+    @Test
+    public void isValidTest_unbound_binder() {
+        binder.forField(nameField)
+                .withValidator(Validator.from(
+                        name -> !name.equals("fail field validation"), ""))
+                .bind(Person::getFirstName, Person::setFirstName);
+
+        Assert.assertTrue(binder.isValid());
+
+        nameField.setValue("fail field validation");
+        Assert.assertFalse(binder.isValid());
+
+        nameField.setValue("");
+        Assert.assertTrue(binder.isValid());
+    }
+
+    @Test(expected = IllegalStateException.class)
+    public void isValidTest_unbound_binder_throws_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();
+    }
 }
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