com.palantir.baseline-error-prone

The com.palantir.baseline-error-prone plugin brings in the net.ltgt.errorprone-javacplugin plugin. The minimal setup is as follows:

apply plugin: 'com.palantir.baseline-error-prone'

Error-prone rules can be suppressed on a per-line or per-block basis just like Checkstyle rules:

@SuppressWarnings("Slf4jConstantLogMessage")

Rules can be suppressed at the project level, or have their severity modified, by adding the following to the project's build.gradle:

tasks.withType(JavaCompile).configureEach(new Action<Task>() {
    public void execute(Task task) {
        task.options.errorprone.disable 'Slf4jLogsafeArgs'
    }
})

To turn all of error-prone's warnings into errors:

allprojects {
    tasks.withType(JavaCompile) {
        options.compilerArgs += ['-Werror']
    }
}

More information on error-prone severity handling can be found at errorprone.info/docs/flags.

Baseline error-prone checks

Baseline configures the following checks in addition to the error-prone's out-of-the-box checks:

• DangerousParallelStreamUsage: Discourage the use of Java parallel streams.
• Slf4jConstantLogMessage: Allow only compile-time constant slf4j log message strings.
• Slf4jLevelCheck: Slf4j level checks (if (log.isInfoEnabled()) {) must match the most severe level in the containing block.
• Slf4jLogsafeArgs: Allow only com.palantir.logsafe.Arg types as parameter inputs to slf4j log messages. More information on Safe Logging can be found at github.com/palantir/safe-logging.
• PreferCollectionTransform: Prefer Guava's Lists.transform or Collections2.transform instead of Iterables.transform when first argument's declared type is a List or Collection type for performance reasons.
• PreferListsPartition: Prefer Guava's Lists.partition(List, int) instead of Iterables.partition(Iterable, int) when first argument's declared type is a list for performance reasons.
• PreferSafeLoggableExceptions: Users should throw SafeRuntimeException instead of RuntimeException so that messages will not be needlessly redacted when logs are collected:

  -throw new RuntimeException("explanation", e); // this message will be redacted when logs are collected
  +throw new SafeRuntimeException("explanation", e); // this message will be preserved (allowing easier debugging)

• PreferSafeLoggingPreconditions: Users should use the safe-logging versions of Precondition checks for standardization when there is equivalent functionality

  -com.google.common.base.Preconditions.checkNotNull(variable, "message");
  +com.palantir.logsafe.Preconditions.checkNotNull(variable, "message"); // equivalent functionality is available in the safe-logging variant

• PreferUncheckedIoExcepetion: Prefer UncheckedIOException or SafeUncheckedIoException when wrapping IOException.
• ShutdownHook: Applications should not use Runtime#addShutdownHook.
• GradleCacheableTaskAction: Gradle plugins should not call Task.doFirst or Task.doLast with a lambda, as that is not cacheable. See gradle/gradle#5510 for more details.
• PreferBuiltInConcurrentKeySet: Discourage relying on Guava's com.google.common.collect.Sets.newConcurrentHashSet(), when Java's java.util.concurrent.ConcurrentHashMap.newKeySet() serves the same purpose.
• JUnit5RuleUsage: Prevent accidental usage of org.junit.Rule/org.junit.ClassRule within Junit5 tests
• DangerousCompletableFutureUsage: Disallow CompletableFuture asynchronous operations without an Executor.
• NonComparableStreamSort: Stream.sorted() should only be called on streams of Comparable types.
• DangerousStringInternUsage: Disallow String.intern() invocations in favor of more predictable, scalable alternatives.
• OptionalOrElseThrowThrows: Optional.orElseThrow argument must return an exception, not throw one.
• OptionalOrElseGetValue: Prefer Optional.orElse(value) over Optional.orElseGet(() -> value) for trivial expressions.
• OptionalOrElseMethodInvocation: Prefer Optional.orElseGet(() -> methodInvocation()) over Optional.orElse(methodInvocation()).
• LambdaMethodReference: Lambda should use a method reference.
• SafeLoggingExceptionMessageFormat: SafeLoggable exceptions do not interpolate parameters.
• StrictUnusedVariable: Functions shouldn't have unused parameters.
• StringBuilderConstantParameters: StringBuilder with a constant number of parameters should be replaced by simple concatenation.
• JUnit5SuiteMisuse: When migrating from JUnit4 -> JUnit5, classes annotated with @RunWith(Suite.class) are dangerous because if they reference any JUnit5 test classes, these tests will silently not run!
• ThrowError: Prefer throwing a RuntimeException rather than Error.
• DnsLookup: Calling new InetSocketAddress(host, port) results in a DNS lookup which prevents the address from following DNS changes.
• ReverseDnsLookup: Calling address.getHostName may result in an unexpected DNS lookup.
• ReadReturnValueIgnored: The result of a read call must be checked to know if EOF has been reached or the expected number of bytes have been consumed.
• FinalClass: A class should be declared final if all of its constructors are private.
• RedundantModifier: Avoid using redundant modifiers.
• StrictCollectionIncompatibleType: Likely programming error due to using the wrong type in a method that accepts Object.
• InvocationHandlerDelegation: InvocationHandlers which delegate to another object must catch and unwrap InvocationTargetException.
• Slf4jThrowable: Slf4j loggers require throwables to be the last parameter otherwise a stack trace is not produced.
• JooqResultStreamLeak: Autocloseable streams and cursors from jOOQ results should be obtained in a try-with-resources statement.
• StreamOfEmpty: Stream.of() should be replaced with Stream.empty() to avoid unnecessary varargs allocation.
• RedundantMethodReference: Redundant method reference to the same type.
• ExceptionSpecificity: Prefer more specific catch types than Exception and Throwable.
• ThrowSpecificity: Prefer to declare more specific throws types than Exception and Throwable.
• UnsafeGaugeRegistration: Use TaggedMetricRegistry.registerWithReplacement over TaggedMetricRegistry.gauge.
• CollectionStreamForEach: Collection.forEach is more efficient than Collection.stream().forEach.
• LoggerEnclosingClass: Loggers created using getLogger(Class<?>) must reference their enclosing class.
• UnnecessaryLambdaArgumentParentheses: Lambdas with a single parameter do not require argument parentheses.
• RawTypes: Avoid raw types; add appropriate type parameters if possible.
• VisibleForTestingPackagePrivate: @VisibleForTesting members should be package-private.
• OptionalFlatMapOfNullable: Optional.map functions may return null to safely produce an empty result.
• ExtendsErrorOrThrowable: Avoid extending Error (or subclasses of it) or Throwable directly.
• ImmutablesStyle: Disallow the use of inline immutables style annotations to avoid forcing compile dependencies on consumers.
• ImmutablesReferenceEquality: Comparison of Immutables value using reference equality instead of value equality.
• TooManyArguments: Prefer Interface that take few arguments rather than many.
• ObjectsHashCodeUnnecessaryVarargs: java.util.Objects.hash(non-varargs) should be replaced with java.util.Objects.hashCode(value) to avoid unnecessary varargs array allocations.
• PreferStaticLoggers: Prefer static loggers over instance loggers.
• LogsafeArgName: Prevent certain named arguments as being logged as safe. Specify unsafe argument names using LogsafeArgName:UnsafeArgNames errorProne flag.
• ImplicitPublicBuilderConstructor: Prevent builders from unintentionally leaking public constructors.
• ImmutablesBuilderMissingInitialization: Prevent building Immutables.org builders when not all fields have been populated.
• UnnecessarilyQualified: Types should not be qualified if they are also imported.
• DeprecatedGuavaObjects: com.google.common.base.Objects has been obviated by java.util.Objects.
• JavaTimeSystemDefaultTimeZone: Avoid using the system default time zone.
• ZoneIdConstant: Prefer ZoneId constants.
• IncubatingMethod: Prevents calling Conjure incubating APIs unless you explicitly opt-out of the check on a per-use or per-project basis.
• CompileTimeConstantViolatesLiskovSubstitution: Requires consistent application of the @CompileTimeConstant annotation to resolve inconsistent validation based on the reference type on which the met is invoked.
• ConsistentLoggerName: Ensure Loggers are named consistently.
• PreferImmutableStreamExCollections: It's common to use toMap/toSet/toList() as the terminal operation on a stream, but would be extremely surprising to rely on the mutability of these collections. Prefer toImmutableMap, toImmutableSet and toImmutableList. (If the performance overhead of a stream is already acceptable, then the UnmodifiableFoo wrapper is likely tolerable).
• DangerousIdentityKey: Key type does not override equals() and hashCode, so comparisons will be done on reference equality only.
• DangerousRecordArrayField: Array fields in records perform reference equality when comparing records.
• ConsistentOverrides: Ensure values are bound to the correct variables when overriding methods
• FilterOutputStreamSlowMultibyteWrite: Subclasses of FilterOutputStream should provide a more efficient implementation of write(byte[], int, int) to avoid slow writes.
• BugCheckerAutoService: Concrete BugChecker implementations should be annotated @AutoService(BugChecker.class) for auto registration with error-prone.
• DangerousCollapseKeysUsage: Disallow usage of EntryStream#collapseKeys().
• JooqBatchWithoutBindArgs: jOOQ batch methods that execute without bind args can cause performance problems.
• InvocationTargetExceptionGetTargetException: InvocationTargetException.getTargetException() predates the general-purpose exception chaining facility. The Throwable.getCause() method is now the preferred means of obtaining this information. (source)
• PreferInputStreamTransferTo: Prefer JDK InputStream.transferTo(OutputStream) over utility methods such as com.google.common.io.ByteStreams.copy(InputStream, OutputStream), org.apache.commons.io.IOUtils.copy(InputStream, OutputStream), org.apache.commons.io.IOUtils.copyLong(InputStream, OutputStream).
• ConjureEndpointDeprecatedForRemoval: Conjure endpoints marked with Deprecated and forRemoval = true should not be used as they are scheduled to be removed.
• ResourceIdentifierGetEqualsUsage: Use ResourceIdentifier#has{Instance,Locator,Service,Type} to avoid allocation when checking RID component equality.
• DeprecatedApiUsage and DeprecatedForRemovalApiUsage: Usage of APIs marked as @Deprecated or @Deprecated(forRemoval = true) is discouraged. These checks replace the build-in compiler checks, that are enabled with the -Xlint:deprecation and -Xlint:removal (default on) flags, to allow for auto-suppression upon library upgrades that newly deprecate APIs.

Programmatic Application

There exist a number of programmatic code modifications available via error-prone. You can run these on your code to apply some refactorings automatically:

./gradlew compileJava compileTestJava -PerrorProneApply

You may apply specific error-prone refactors including those which are not enabled by default by providing a comma delimited list of check names to the -PerrorProneApply option.

./gradlew compileJava compileTestJava -PerrorProneApply=ThrowSpecificity