Configure Nullabillity checks with NullAway

This commit configures the Errorprone and Nullaway plugins in the build
to automatically check for null safety issues in the codebase.

Closes gh-1204

build.gradle

@@ -10,6 +10,7 @@ ext {
 subprojects {
 	apply plugin: 'org.springframework.graphql.conventions'
 	apply plugin: 'org.springframework.graphql.architecture'
+	apply plugin: 'org.springframework.graphql.nullability'
 	group = 'org.springframework.graphql'
 
 	ext.javadocLinks = [

buildSrc/build.gradle

@@ -23,6 +23,7 @@ dependencies {
 
 	implementation("org.jetbrains.kotlin:kotlin-gradle-plugin:${kotlinVersion}")
 	implementation("io.spring.javaformat:spring-javaformat-gradle-plugin:${javaFormatVersion}")
+	implementation("net.ltgt.errorprone:net.ltgt.errorprone.gradle.plugin:${errorProneVersion}")
 	implementation "com.tngtech.archunit:archunit:1.4.0"
 }
 
@@ -40,6 +41,10 @@ gradlePlugin {
 			id = "org.springframework.graphql.architecture"
 			implementationClass = "org.springframework.graphql.build.architecture.ArchitecturePlugin"
 		}
+		nullability {
+			id = "org.springframework.graphql.nullability"
+			implementationClass = "org.springframework.graphql.build.nullability.NullabilityPlugin"
+		}
 	}
 }
 

buildSrc/gradle.properties

@@ -1 +1,2 @@
-javaFormatVersion=0.0.43
+javaFormatVersion=0.0.43
+errorProneVersion=4.2.0

buildSrc/src/main/java/org/springframework/graphql/build/architecture/ArchitectureCheck.java

@@ -45,10 +45,12 @@ import org.gradle.api.tasks.SkipWhenEmpty;
 import org.gradle.api.tasks.TaskAction;
 
 import static org.springframework.graphql.build.architecture.ArchitectureRules.allPackagesShouldBeFreeOfTangles;
+import static org.springframework.graphql.build.architecture.ArchitectureRules.classShouldNotUseSpringNullAnnotations;
 import static org.springframework.graphql.build.architecture.ArchitectureRules.classesShouldNotImportForbiddenTypes;
 import static org.springframework.graphql.build.architecture.ArchitectureRules.javaClassesShouldNotImportKotlinAnnotations;
 import static org.springframework.graphql.build.architecture.ArchitectureRules.noClassesShouldCallStringToLowerCaseWithoutLocale;
 import static org.springframework.graphql.build.architecture.ArchitectureRules.noClassesShouldCallStringToUpperCaseWithoutLocale;
+import static org.springframework.graphql.build.architecture.ArchitectureRules.packageInfoShouldBeNullMarked;
 
 /**
  * {@link Task} that checks for architecture problems.
@@ -68,7 +70,9 @@ public abstract class ArchitectureCheck extends DefaultTask {
 				javaClassesShouldNotImportKotlinAnnotations(),
 				allPackagesShouldBeFreeOfTangles(),
 				noClassesShouldCallStringToLowerCaseWithoutLocale(),
-				noClassesShouldCallStringToUpperCaseWithoutLocale());
+				noClassesShouldCallStringToUpperCaseWithoutLocale(),
+				packageInfoShouldBeNullMarked(),
+				classShouldNotUseSpringNullAnnotations());
 		getRuleDescriptions().set(getRules().map((rules) -> rules.stream().map(ArchRule::getDescription).toList()));
 	}
 

buildSrc/src/main/java/org/springframework/graphql/build/architecture/ArchitectureRules.java

@@ -55,9 +55,9 @@ abstract class ArchitectureRules {
 	static ArchRule classShouldNotUseSpringNullAnnotations() {
 		return ArchRuleDefinition.noClasses()
 				.should().dependOnClassesThat()
-				.haveFullyQualifiedName("org.springframework.lang.NonNull")
+				.haveFullyQualifiedName("org.jspecify.annotations.NonNull")
 				.orShould().dependOnClassesThat()
-				.haveFullyQualifiedName("org.springframework.lang.Nullable");
+				.haveFullyQualifiedName("org.jspecify.annotations.Nullable");
 	}
 
 

buildSrc/src/main/java/org/springframework/graphql/build/nullability/NullabilityPlugin.java

@@ -0,0 +1,78 @@
+/*
+ * 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.build.nullability;
+
+import java.util.function.Consumer;
+import java.util.regex.Pattern;
+
+import net.ltgt.gradle.errorprone.ErrorProneOptions;
+import net.ltgt.gradle.errorprone.ErrorPronePlugin;
+import org.gradle.api.Plugin;
+import org.gradle.api.Project;
+import org.gradle.api.artifacts.DependencySet;
+import org.gradle.api.plugins.ExtensionAware;
+import org.gradle.api.plugins.JavaPlugin;
+import org.gradle.api.tasks.compile.CompileOptions;
+import org.gradle.api.tasks.compile.JavaCompile;
+
+/**
+ * {@link Plugin} for enforcing Nullability checks on the source code.
+ *
+ * @author Brian Clozel
+ */
+public class NullabilityPlugin implements Plugin<Project> {
+
+	private static final Pattern COMPILE_MAIN_SOURCES_TASK_NAME = Pattern.compile("compile(\\d+)?Java");
+
+	@Override
+	public void apply(Project project) {
+		project.getPlugins().apply(ErrorPronePlugin.class);
+		DependencySet errorproneConfig = project.getConfigurations().getByName("errorprone").getDependencies();
+		errorproneConfig.add(project.getDependencies().create("com.uber.nullaway:nullaway:0.12.6"));
+		errorproneConfig.add(project.getDependencies().create("com.google.errorprone:error_prone_core:2.37.0"));
+
+		project.getTasks()
+				.withType(JavaCompile.class)
+				.configureEach((javaCompile) -> {
+					if (compilesMainSources(javaCompile)) {
+						doWithErrorProneOptions(javaCompile, (errorProneOptions) -> {
+							errorProneOptions.getDisableAllChecks().set(true);
+							errorProneOptions.option("NullAway:OnlyNullMarked", "true");
+							errorProneOptions.option("NullAway:CustomContractAnnotations", "org.springframework.lang.Contract");
+							errorProneOptions.option("NullAway:JSpecifyMode", "true");
+							errorProneOptions.error("NullAway");
+						});
+					}
+					else {
+						doWithErrorProneOptions(javaCompile, (errorProneOptions) -> {
+							errorProneOptions.getEnabled().set(false);
+						});
+					}
+				});
+	}
+
+	private boolean compilesMainSources(JavaCompile compileTask) {
+		return COMPILE_MAIN_SOURCES_TASK_NAME.matcher(compileTask.getName()).matches();
+	}
+
+	private void doWithErrorProneOptions(JavaCompile compileTask, Consumer<ErrorProneOptions> optionsConsumer) {
+		CompileOptions options = compileTask.getOptions();
+		ErrorProneOptions errorProneOptions = ((ExtensionAware) options).getExtensions().getByType(ErrorProneOptions.class);
+		optionsConsumer.accept(errorProneOptions);
+	}
+
+}