Add isEmpty and ifPresent methods in ArgumentValue

Closes gh-1172

Signed-off-by: James Bodkin <james.bodkin@amphora.net>
[brian.clozel@broadcom.com: add tests and reduce scope]
Signed-off-by: Brian Clozel <brian.clozel@broadcom.com>

spring-graphql/src/main/java/org/springframework/graphql/data/ArgumentValue.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2022 the original author or authors.
+ * Copyright 2002-2025 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -18,8 +18,10 @@ package org.springframework.graphql.data;
 
 
 import java.util.Optional;
+import java.util.function.Consumer;
 
 import org.springframework.lang.Nullable;
+import org.springframework.util.Assert;
 import org.springframework.util.ObjectUtils;
 
 /**
@@ -69,6 +71,15 @@ public final class ArgumentValue<T> {
 		return (this.value != null);
 	}
 
+	/**
+	 * Return {@code true} if the input value was present in the input but the value was {@code null},
+	 * and {@code false} otherwise.
+	 * @since 1.4.0
+	 */
+	public boolean isEmpty() {
+		return !this.omitted && this.value == null;
+	}
+
 	/**
 	 * Return {@code true} if the input value was omitted altogether from the
 	 * input, and {@code false} if it was provided, but possibly set to the
@@ -93,6 +104,17 @@ public final class ArgumentValue<T> {
 		return Optional.ofNullable(this.value);
 	}
 
+	/**
+	 * If a value is present, performs the given action with the value, otherwise does nothing.
+	 * @param action the action to be performed, if a value is present
+	 */
+	public void ifPresent(Consumer<? super T> action) {
+		Assert.notNull(action, "Action is required");
+		if (this.value != null) {
+			action.accept(this.value);
+		}
+	}
+
 	@Override
 	public boolean equals(Object other) {
 		// This covers OMITTED constant

spring-graphql/src/test/java/org/springframework/graphql/data/ArgumentValueTests.java

@@ -0,0 +1,84 @@
+/*
+ * Copyright 2020-2025 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.graphql.data;
+
+import java.util.concurrent.atomic.AtomicBoolean;
+
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Tests for {@link ArgumentValue}.
+ * @author Brian Clozel
+ */
+class ArgumentValueTests {
+
+	@Test
+	void existingValueShouldBePresent() {
+		ArgumentValue<String> message = ArgumentValue.ofNullable("hello");
+		assertThat(message.isOmitted()).isFalse();
+		assertThat(message.isPresent()).isTrue();
+		assertThat(message.isEmpty()).isFalse();
+	}
+
+	@Test
+	void nullValueShouldBePresent() {
+		ArgumentValue<String> message = ArgumentValue.ofNullable(null);
+		assertThat(message.isOmitted()).isFalse();
+		assertThat(message.isPresent()).isFalse();
+		assertThat(message.isEmpty()).isTrue();
+	}
+
+	@Test
+	void noValueShouldBeOmitted() {
+		ArgumentValue<String> message = ArgumentValue.omitted();
+		assertThat(message.isOmitted()).isTrue();
+		assertThat(message.isPresent()).isFalse();
+		assertThat(message.isEmpty()).isFalse();
+	}
+
+	@Test
+	void asOptionalShouldMapOmitted() {
+		assertThat(ArgumentValue.omitted().asOptional()).isEmpty();
+		assertThat(ArgumentValue.ofNullable(null).asOptional()).isEmpty();
+		assertThat(ArgumentValue.ofNullable("hello").asOptional()).isPresent();
+	}
+
+	@Test
+	void ifPresentShouldExecuteWhenValue() {
+		AtomicBoolean called = new AtomicBoolean();
+		ArgumentValue.ofNullable("hello").ifPresent(value -> called.set(true));
+		assertThat(called.get()).isTrue();
+	}
+
+	@Test
+	void ifPresentShouldSkipWhenNull() {
+		AtomicBoolean called = new AtomicBoolean();
+		ArgumentValue.ofNullable(null).ifPresent(value -> called.set(true));
+		assertThat(called.get()).isFalse();
+	}
+
+	@Test
+
+	void ifPresentShouldSkipWhenOmitted() {
+		AtomicBoolean called = new AtomicBoolean();
+		ArgumentValue.omitted().ifPresent(value -> called.set(true));
+		assertThat(called.get()).isFalse();
+	}
+
+}