feat: Use binding object to check for Binder#hasChanges

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

@@ -282,6 +282,18 @@ default BindingValidationStatus<TARGET> validate() {
          * @return A boolean value
          */
         boolean isConvertBackToPresentation();
+
+        /**
+         * Checks whether the field that the binding uses has uncommitted
+         * changes.
+         *
+         * @throws IllegalStateException
+         *             if the binding is no longer attached to a Binder.
+         *
+         * @return {@literal true} if the field the binding uses has uncommitted
+         *         changes, otherwise {@literal false}.
+         */
+        boolean hasChanges();
     }
 
     /**
@@ -1589,6 +1601,16 @@ private <T> T execute(Supplier<T> supplier) {
                 }
             }
         }
+
+        @Override
+        public boolean hasChanges() throws IllegalStateException {
+            if (this.binder == null) {
+                throw new IllegalStateException(
+                        "This Binding is no longer attached to a Binder");
+            }
+
+            return this.binder.hasChanges(this);
+        }
     }
 
     /**
@@ -3034,6 +3056,17 @@ public boolean hasChanges() {
         return !changedBindings.isEmpty();
     }
 
+    /**
+     * Checks whether a bound field has uncomitted changes.
+     *
+     * @param binding
+     *            Binding to be checked
+     * @return true if field has been changed.
+     */
+    public boolean hasChanges(Binding<BEAN, ?> binding) {
+        return hasChanges() && changedBindings.contains(binding);
+    }
+
     /**
      * Sets the read only state to the given value for all currently bound
      * fields.

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

@@ -65,6 +65,7 @@
 import static org.junit.Assert.assertNull;
 import static org.junit.Assert.assertSame;
 import static org.junit.Assert.assertTrue;
+import static org.junit.Assert.assertThrows;
 
 public class BinderTest extends BinderTestBase<Binder<Person>, Person> {
 
@@ -199,6 +200,75 @@ public void clearBean_setsHasChangesToFalse() {
 
     }
 
+    @Test
+    public void bindingHasChanges_trueWhenFieldValueChanges() {
+        var binding = binder.forField(nameField).bind(Person::getFirstName,
+                Person::setFirstName);
+
+        binder.readBean(item);
+        assertEquals("No name field value", "Johannes", nameField.getValue());
+        assertFalse("Field marked as changed after reading bean",
+                binder.hasChanges(binding));
+
+        ageField.setValue("99");
+        assertFalse("Age field caused name field change",
+                binder.hasChanges(binding));
+
+        nameField.setValue("James");
+        assertTrue("Binder did not have value changes",
+                binder.hasChanges(binding));
+
+        binder.readBean(null);
+
+        assertFalse("Binder has changes after clearing all fields",
+                binder.hasChanges(binding));
+
+    }
+
+    @Test
+    public void bindingInstanceHasChanges_trueWhenFieldValueChanges() {
+        var binding = binder.forField(nameField).bind(Person::getFirstName,
+                Person::setFirstName);
+
+        binder.readBean(item);
+
+        assertEquals("No name field value", "Johannes", nameField.getValue());
+        assertFalse("Field marked as changed after reading bean",
+                binding.hasChanges());
+
+        ageField.setValue("99");
+        assertFalse("Age field caused name field change", binding.hasChanges());
+
+        nameField.setValue("James");
+        assertTrue("Binder did not have value changes", binding.hasChanges());
+
+        binder.readBean(null);
+
+        assertFalse("Binder has changes after clearing all fields",
+                binding.hasChanges());
+    }
+
+    @Test
+    public void bindingInstanceHasChanges_throwsWhenBinderNotAttached() {
+        var binding = binder.forField(nameField).bind(Person::getFirstName,
+                Person::setFirstName);
+
+        binder.readBean(item);
+
+        assertFalse("Field marked as changed after reading bean",
+                binding.hasChanges());
+
+        nameField.setValue("James");
+        assertTrue("Binder did not have value changes", binding.hasChanges());
+
+        binding.unbind();
+
+        assertThrows("Expect unbound binding to throw exception",
+                IllegalStateException.class, () -> {
+                    binding.hasChanges();
+                });
+    }
+
     @Test
     public void clearReadOnlyBinder_shouldClearFields() {
         binder.forField(nameField).bind(Person::getFirstName,