Turn on @var check and fixup other error-prone warnings

build.gradle

@@ -437,27 +437,26 @@ subprojects { subproj ->
 				'-Xep:ThrowsUncheckedException:OFF',
 
 				// we do not follow Google Java Style Guide
-				'-Xep:UngroupedOverloads:OFF',
-
-				'-Xep:Var:OFF'
+				'-Xep:UngroupedOverloads:OFF'
 			]
 		}
 		compileTestJava {
 			options.compilerArgs += [
 				'-XepAllDisabledChecksAsWarnings',
 
-				// many nested test classes are non-static for testing reasons
+				// these checks are often violated on purpose for testing reasons
 				'-Xep:ClassCanBeStatic:OFF',
-
+				'-Xep:ConstantField:OFF',
+				'-Xep:ConstructorInvokesOverridable:OFF',
 				'-Xep:ConstructorLeaksThis:OFF',
-
-				// produces many warnings, none critical
-				// TODO: investigate if this check is worth having on for tests
 				'-Xep:MethodCanBeStatic:OFF',
-
+				'-Xep:PrivateConstructorForUtilityClass:OFF',
 				'-Xep:StaticOrDefaultInterfaceMethod:OFF',
 				'-Xep:ThrowsUncheckedException:OFF',
 				'-Xep:UngroupedOverloads:OFF',
+
+				// produces lots of warnings, none critical but potentially useful
+				// TODO: investigate if its worth turning this check on for tests
 				'-Xep:Var:OFF'
 			]
 		}

junit-jupiter-api/src/main/java/org/junit/jupiter/api/AssertIterableEquals.java

@@ -23,6 +23,8 @@
 import java.util.concurrent.atomic.AtomicInteger;
 import java.util.function.Supplier;
 
+import com.google.errorprone.annotations.Var;
+
 /**
  * {@code AssertIterable} is a collection of utility methods that support asserting
  * Iterable equality in tests.
@@ -60,6 +62,7 @@ private static void assertIterableEquals(Iterable<?> expected, Iterable<?> actua
 		Iterator<?> expectedIterator = expected.iterator();
 		Iterator<?> actualIterator = actual.iterator();
 
+		@Var
 		int processed = 0;
 		while (expectedIterator.hasNext() && actualIterator.hasNext()) {
 			processed++;

junit-jupiter-api/src/main/java/org/junit/jupiter/api/AssertLinesMatch.java

@@ -20,6 +20,8 @@
 import java.util.List;
 import java.util.regex.PatternSyntaxException;
 
+import com.google.errorprone.annotations.Var;
+
 /**
  * {@code AssertLinesMatch} is a collection of utility methods that support asserting
  * lines of {@link String} equality or {@link java.util.regex.Pattern}-match in tests.
@@ -55,6 +57,7 @@ static void assertLinesMatch(List<String> expectedLines, List<String> actualLine
 
 		// simple case: both list are equally sized, compare them line-by-line
 		if (expectedSize == actualSize) {
+			@Var
 			boolean allOk = true;
 			for (int i = 0; i < expectedSize; i++) {
 				if (matches(expectedLines.get(i), actualLines.get(i))) {
@@ -76,6 +79,7 @@ private static void assertLinesMatchWithFastForward(List<String> expectedLines,
 		Deque<String> actualDeque = new ArrayDeque<>(actualLines);
 
 		main: while (!expectedDeque.isEmpty()) {
+			@Var
 			String expectedLine = expectedDeque.pop();
 			String actualLine = actualDeque.peek();
 
@@ -153,7 +157,7 @@ private static void fail(List<String> expectedLines, List<String> actualLines, S
 		assertEquals(expected, actual, format(format, args));
 	}
 
-	static boolean isFastForwardLine(String line) {
+	static boolean isFastForwardLine(@Var String line) {
 		line = line.trim();
 		return line.length() >= 4 && line.startsWith(">>") && line.endsWith(">>");
 	}

junit-jupiter-api/src/main/java/org/junit/jupiter/api/AssertTimeout.java

@@ -23,6 +23,8 @@
 import java.util.concurrent.TimeoutException;
 import java.util.function.Supplier;
 
+import com.google.errorprone.annotations.Var;
+
 import org.junit.jupiter.api.function.Executable;
 import org.junit.jupiter.api.function.ThrowingSupplier;
 import org.junit.platform.commons.util.ExceptionUtils;
@@ -68,6 +70,7 @@ static <T> T assertTimeout(Duration timeout, ThrowingSupplier<T> supplier, Strin
 	static <T> T assertTimeout(Duration timeout, ThrowingSupplier<T> supplier, Supplier<String> messageSupplier) {
 		long timeoutInMillis = timeout.toMillis();
 		long start = System.currentTimeMillis();
+		@Var
 		T result = null;
 		try {
 			result = supplier.get();

junit-jupiter-engine/src/main/java/org/junit/jupiter/engine/descriptor/AbstractExtensionContext.java

@@ -17,6 +17,8 @@
 import java.util.Optional;
 import java.util.Set;
 
+import com.google.errorprone.annotations.Var;
+
 import org.junit.jupiter.api.extension.ExtensionContext;
 import org.junit.jupiter.engine.execution.ExtensionValuesStore;
 import org.junit.jupiter.engine.execution.NamespaceAwareStore;
@@ -45,6 +47,7 @@ abstract class AbstractExtensionContext<T extends TestDescriptor> implements Ext
 	}
 
 	private static ExtensionValuesStore createStore(ExtensionContext parent) {
+		@Var
 		ExtensionValuesStore parentStore = null;
 		if (parent != null) {
 			parentStore = ((AbstractExtensionContext<?>) parent).valuesStore;
@@ -74,6 +77,7 @@ public Optional<ExtensionContext> getParent() {
 
 	@Override
 	public ExtensionContext getRoot() {
+		@Var
 		ExtensionContext root = this;
 		while (parent != null && parent != root) {
 			root = parent;

junit-jupiter-engine/src/main/java/org/junit/jupiter/engine/descriptor/ClassTestDescriptor.java

@@ -24,6 +24,8 @@
 import java.util.Set;
 import java.util.function.Function;
 
+import com.google.errorprone.annotations.Var;
+
 import org.junit.jupiter.api.TestInstance;
 import org.junit.jupiter.api.TestInstance.Lifecycle;
 import org.junit.jupiter.api.extension.AfterAllCallback;
@@ -286,6 +288,7 @@ private static AfterEachMethodAdapter synthesizeAfterEachMethodAdapter(Method me
 	private static void invokeMethodInExtensionContext(Method method, ExtensionContext context,
 			ExtensionRegistry registry) {
 
+		@Var
 		Object testInstance = context.getRequiredTestInstance();
 		testInstance = ReflectionUtils.getOutermostInstance(testInstance, method.getDeclaringClass()).orElseThrow(
 			() -> new JUnitException("Failed to find instance for method: " + method.toGenericString()));

junit-jupiter-engine/src/main/java/org/junit/jupiter/engine/descriptor/TestFactoryTestDescriptor.java

@@ -16,6 +16,8 @@
 import java.util.Iterator;
 import java.util.stream.Stream;
 
+import com.google.errorprone.annotations.Var;
+
 import org.junit.jupiter.api.DynamicContainer;
 import org.junit.jupiter.api.DynamicNode;
 import org.junit.jupiter.api.DynamicTest;
@@ -72,6 +74,7 @@ protected void invokeTestMethod(JupiterEngineExecutionContext context, DynamicTe
 			TestSource source = getSource().orElseThrow(
 				() -> new JUnitException("Illegal state: TestSource must be present"));
 			try (Stream<DynamicNode> dynamicNodeStream = toDynamicNodeStream(testFactoryMethodResult)) {
+				@Var
 				int index = 1;
 				Iterator<DynamicNode> iterator = dynamicNodeStream.iterator();
 				while (iterator.hasNext()) {

junit-jupiter-engine/src/main/java/org/junit/jupiter/engine/execution/ConditionEvaluator.java

@@ -20,6 +20,8 @@
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
 
+import com.google.errorprone.annotations.Var;
+
 import org.junit.jupiter.api.extension.ConditionEvaluationResult;
 import org.junit.jupiter.api.extension.ExecutionCondition;
 import org.junit.jupiter.api.extension.ExtensionContext;
@@ -115,7 +117,7 @@ private static String getDeactivatePatternString(ConfigurationParameters configu
 	 * See {@link Constants#DEACTIVATE_CONDITIONS_PATTERN_PROPERTY_NAME} for
 	 * details on the pattern matching syntax.
 	 */
-	private static String convertToRegEx(String pattern) {
+	private static String convertToRegEx(@Var String pattern) {
 		pattern = Matcher.quoteReplacement(pattern);
 
 		// Match "." against "." and "$" since users may declare a "." instead of a

junit-jupiter-engine/src/main/java/org/junit/jupiter/engine/execution/ExecutableInvoker.java

@@ -23,6 +23,8 @@
 import java.util.Optional;
 import java.util.logging.Logger;
 
+import com.google.errorprone.annotations.Var;
+
 import org.junit.jupiter.api.extension.ExtensionContext;
 import org.junit.jupiter.api.extension.ParameterContext;
 import org.junit.jupiter.api.extension.ParameterResolutionException;
@@ -157,6 +159,7 @@ private static Object[] resolveParameters(Executable executable, Optional<Object
 
 		Parameter[] parameters = executable.getParameters();
 		Object[] values = new Object[parameters.length];
+		@Var
 		int start = 0;
 
 		// Ensure that the outer instance is resolved as the first parameter if

junit-jupiter-engine/src/main/java/org/junit/jupiter/engine/execution/ExtensionValuesStore.java

@@ -19,6 +19,8 @@
 import java.util.Objects;
 import java.util.function.Function;
 
+import com.google.errorprone.annotations.Var;
+
 import org.junit.jupiter.api.extension.ExtensionContext;
 import org.junit.jupiter.api.extension.ExtensionContext.Namespace;
 import org.junit.jupiter.api.extension.ExtensionContextException;
@@ -68,6 +70,7 @@ <T> T get(Namespace namespace, Object key, Class<T> requiredType) {
 
 	<K, V> Object getOrComputeIfAbsent(Namespace namespace, K key, Function<K, V> defaultCreator) {
 		synchronized (this.monitor) {
+			@Var
 			StoredValue storedValue = getStoredValue(namespace, key);
 			if (storedValue == null) {
 				if (this.parentStore != null) {

junit-jupiter-engine/src/test/java/org/junit/jupiter/api/AssertionTestUtils.java

@@ -18,12 +18,6 @@
 
 class AssertionTestUtils {
 
-	///CLOVER:OFF
-	private AssertionTestUtils() {
-		/* no-op */
-	}
-	///CLOVER:ON
-
 	static void expectAssertionFailedError() {
 		throw new AssertionError("Should have thrown an " + AssertionFailedError.class.getName());
 	}

junit-jupiter-engine/src/test/java/org/junit/jupiter/api/IterableFactory.java

@@ -17,12 +17,6 @@
 
 final class IterableFactory {
 
-	///CLOVER:OFF
-	private IterableFactory() {
-		/* no-op */
-	}
-	///CLOVER:ON
-
 	static List<Object> listOf(Object... objects) {
 		return Arrays.asList(objects);
 	}

junit-jupiter-migrationsupport/src/test/java/org/junit/jupiter/migrationsupport/rules/FailAfterAllHelper.java

@@ -12,12 +12,6 @@
 
 class FailAfterAllHelper {
 
-	///CLOVER:OFF
-	private FailAfterAllHelper() {
-		/* no-op */
-	}
-	///CLOVER:ON
-
 	static void fail() {
 		// hack: use this blacklisted exception to fail the build, all others would be swallowed...
 		throw new OutOfMemoryError("a postcondition was violated");

junit-jupiter-params/src/main/java/org/junit/jupiter/params/ParameterizedTestNameFormatter.java

@@ -15,6 +15,8 @@
 import java.text.MessageFormat;
 import java.util.stream.IntStream;
 
+import com.google.errorprone.annotations.Var;
+
 import org.junit.platform.commons.JUnitException;
 import org.junit.platform.commons.util.StringUtils;
 
@@ -36,6 +38,7 @@ String format(int invocationIndex, Object... arguments) {
 	}
 
 	private String prepareMessageFormatPattern(int invocationIndex, Object[] arguments) {
+		@Var
 		String result = namePattern.replace("{index}", String.valueOf(invocationIndex));
 		if (result.contains("{arguments}")) {
 			// @formatter:off

junit-platform-commons/src/main/java/org/junit/platform/commons/util/AnnotationUtils.java

@@ -33,6 +33,8 @@
 import java.util.Set;
 import java.util.concurrent.ConcurrentHashMap;
 
+import com.google.errorprone.annotations.Var;
+
 import org.junit.platform.commons.JUnitException;
 import org.junit.platform.commons.meta.API;
 import org.junit.platform.commons.util.ReflectionUtils.HierarchyTraversalMode;
@@ -83,6 +85,7 @@ public static <T> Optional<T> getDefaultValue(Annotation annotation, String attr
 		Preconditions.notNull(attributeType, "attributeType must not be null");
 
 		Class<? extends Annotation> annotationType = annotation.annotationType();
+		@Var
 		Method attribute = null;
 		try {
 			attribute = annotationType.getDeclaredMethod(attributeName);
@@ -165,6 +168,7 @@ private static <A extends Annotation> Optional<A> findAnnotation(AnnotatedElemen
 
 		// Cached?
 		AnnotationCacheKey key = new AnnotationCacheKey(element, annotationType);
+		@Var
 		A annotation = (A) annotationCache.get(key);
 		if (annotation != null) {
 			return Optional.of(annotation);

junit-platform-commons/src/main/java/org/junit/platform/commons/util/ClassLoaderUtils.java

@@ -16,6 +16,8 @@
 import java.security.CodeSource;
 import java.util.Optional;
 
+import com.google.errorprone.annotations.Var;
+
 import org.junit.platform.commons.meta.API;
 
 /**
@@ -61,6 +63,7 @@ public static ClassLoader getDefaultClassLoader() {
 	public static Optional<URL> getLocation(Object object) {
 		Preconditions.notNull(object, "object must not be null");
 		// determine class loader
+		@Var
 		ClassLoader loader = object.getClass().getClassLoader();
 		if (loader == null) {
 			loader = ClassLoader.getSystemClassLoader();
@@ -70,8 +73,7 @@ public static Optional<URL> getLocation(Object object) {
 		}
 		// try finding resource by name
 		if (loader != null) {
-			String name = object.getClass().getName();
-			name = name.replace(".", "/") + ".class";
+			String name = object.getClass().getName().replace(".", "/") + ".class";
 			try {
 				return Optional.ofNullable(loader.getResource(name));
 			}

junit-platform-commons/src/main/java/org/junit/platform/commons/util/ClasspathScanner.java

@@ -36,6 +36,8 @@
 import java.util.logging.Logger;
 import java.util.stream.Stream;
 
+import com.google.errorprone.annotations.Var;
+
 import org.junit.platform.commons.meta.API;
 
 /**
@@ -70,7 +72,7 @@ class ClasspathScanner {
 		this.loadClass = loadClass;
 	}
 
-	List<Class<?>> scanForClassesInPackage(String basePackageName, Predicate<Class<?>> classFilter,
+	List<Class<?>> scanForClassesInPackage(@Var String basePackageName, Predicate<Class<?>> classFilter,
 			Predicate<String> classNameFilter) {
 
 		PackageUtils.assertPackageNameIsValid(basePackageName);
@@ -137,6 +139,7 @@ private List<Class<?>> findClassesForPath(Path baseDir, String basePackageName,
 
 	private void processClassFileSafely(Path baseDir, String basePackageName, Predicate<Class<?>> classFilter,
 			Predicate<String> classNameFilter, Path classFile, Consumer<Class<?>> classConsumer) {
+		@Var
 		Optional<Class<?>> clazz = Optional.empty();
 		try {
 			String fullyQualifiedClassName = determineFullyQualifiedClassName(baseDir, basePackageName, classFile);
@@ -173,6 +176,7 @@ private static String determineSimpleClassName(Path classFile) {
 	private static String determineSubpackageName(Path baseDir, Path classFile) {
 		Path relativePath = baseDir.relativize(classFile.getParent());
 		String pathSeparator = baseDir.getFileSystem().getSeparator();
+		@Var
 		String subpackageName = relativePath.toString().replace(pathSeparator, PACKAGE_SEPARATOR_STRING);
 		if (subpackageName.endsWith(pathSeparator)) {
 			// Workaround for JDK bug: https://bugs.openjdk.java.net/browse/JDK-8153248

junit-platform-commons/src/main/java/org/junit/platform/commons/util/ReflectionUtils.java

@@ -46,6 +46,8 @@
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
 
+import com.google.errorprone.annotations.Var;
+
 import org.junit.platform.commons.JUnitException;
 import org.junit.platform.commons.meta.API;
 
@@ -383,7 +385,7 @@ public static Optional<Class<?>> loadClass(String name) {
 	 * @param classLoader the {@code ClassLoader} to use; never {@code null}
 	 * @see #loadClass(String)
 	 */
-	public static Optional<Class<?>> loadClass(String name, ClassLoader classLoader) {
+	public static Optional<Class<?>> loadClass(@Var String name, ClassLoader classLoader) {
 		Preconditions.notBlank(name, "Class name must not be null or blank");
 		Preconditions.notNull(classLoader, "ClassLoader must not be null");
 		name = name.trim();
@@ -393,6 +395,7 @@ public static Optional<Class<?>> loadClass(String name, ClassLoader classLoader)
 		}
 
 		try {
+			@Var
 			Matcher matcher;
 
 			// Primitive arrays such as "[I", "[[[[D", etc.
@@ -795,6 +798,7 @@ private static List<Method> findAllMethodsInHierarchy(Class<?> clazz, HierarchyT
 	private static int defaultMethodSorter(Method method1, Method method2) {
 		String name1 = method1.getName();
 		String name2 = method2.getName();
+		@Var
 		int comparison = Integer.compare(name1.hashCode(), name2.hashCode());
 		if (comparison == 0) {
 			comparison = name1.compareTo(name2);