Configure Errorprone in build

Also fixes ERROR severity bug patterns.

Author: shakuzen

build.gradle

@@ -8,6 +8,7 @@ buildscript {
     }
 
     dependencies {
+        classpath libs.plugin.errorprone
         classpath libs.plugin.license
         classpath libs.plugin.nebulaRelease
         classpath libs.plugin.nebulaPublishing
@@ -61,6 +62,7 @@ allprojects {
 }
 
 subprojects {
+    apply plugin: 'net.ltgt.errorprone'
     apply plugin: 'signing'
     apply plugin: 'io.spring.javaformat'
     apply plugin: 'com.diffplug.spotless'
@@ -103,6 +105,7 @@ subprojects {
             // JSR-305 only used for non-required meta-annotations
             optionalApi libs.jsr305
             checkstyle libs.spring.javaformatCheckstyle
+            errorprone(libs.errorprone)
         }
 
         tasks {

gradle/libs.versions.toml

@@ -102,6 +102,7 @@ dropwizardMetricsCore5 = { module = "io.dropwizard.metrics5:metrics-core", versi
 dynatraceUtils = { module = "com.dynatrace.metric.util:dynatrace-metric-utils-java", version.ref = "dynatrace-utils" }
 ehcache2 = { module = "net.sf.ehcache:ehcache", version.ref = "ehcache2" }
 ehcache3 = { module = "org.ehcache:ehcache", version.ref = "ehcache3" }
+errorprone = { module = "com.google.errorprone:error_prone_core", version = "2.37.0" }
 felixFramework = "org.apache.felix:org.apache.felix.framework:7.0.5"
 felixScr = "org.apache.felix:org.apache.felix.scr:2.2.12"
 gmetric4j = { module = "info.ganglia.gmetric4j:gmetric4j", version.ref = "gmetric4j" }
@@ -213,6 +214,7 @@ wiremock = { module = "com.github.tomakehurst:wiremock-jre8-standalone", version
 wiremockJunit5 = { module = "ru.lanwen.wiremock:wiremock-junit5", version.ref = "wiremock-junit5" }
 
 # plugin dependencies
+plugin-errorprone = { module = "net.ltgt.errorprone:net.ltgt.errorprone.gradle.plugin", version = "4.1.0" }
 plugin-license = { module = "gradle.plugin.com.hierynomus.gradle.plugins:license-gradle-plugin", version = "0.16.1" }
 plugin-nebulaRelease = { module = "com.netflix.nebula:nebula-release-plugin", version = "18.0.8" }
 plugin-nebulaPublishing = { module = "com.netflix.nebula:nebula-publishing-plugin", version = "20.3.0" }

implementations/micrometer-registry-elastic/src/main/java/io/micrometer/elastic/ElasticConfig.java

@@ -76,6 +76,7 @@ default String index() {
      * separated by the {@link #indexDateSeparator()}. Default is: "yyyy-MM"
      * @return date format for index
      */
+    @SuppressWarnings("ReturnValueIgnored")
     default String indexDateFormat() {
         return getString(this, "indexDateFormat").invalidateWhen(format -> {
             if (format == null) {
@@ -178,6 +179,7 @@ default String documentType() {
         return getString(this, "documentType").orElse("doc");
     }
 
+    @SuppressWarnings("ReturnValueIgnored")
     @Override
     default Validated<?> validate() {
         return checkAll(this, c -> StepRegistryConfig.validate(c), checkRequired("host", ElasticConfig::host),

micrometer-core/build.gradle

@@ -283,6 +283,11 @@ java11Test {
 }
 
 compileJava11TestJava {
+    options.errorprone.enabled = false
     sourceCompatibility = JavaVersion.VERSION_11
     targetCompatibility = JavaVersion.VERSION_11
 }
+
+compileJava11Java {
+    options.errorprone.enabled = false
+}

micrometer-core/src/main/java/io/micrometer/core/aop/TimedAspect.java

@@ -274,6 +274,7 @@ private void record(ProceedingJoinPoint pjp, Timed timed, String metricName, Tim
 
     private Timer.Builder recordBuilder(ProceedingJoinPoint pjp, Timed timed, String metricName,
             String exceptionClass) {
+        @SuppressWarnings("NullTernary")
         Timer.Builder builder = Timer.builder(metricName)
             .description(timed.description().isEmpty() ? null : timed.description())
             .tags(timed.extraTags())

micrometer-core/src/main/java/io/micrometer/core/instrument/Timer.java

@@ -89,6 +89,7 @@ static ResourceSample resource(MeterRegistry registry, String name) {
      * empty.
      * @return This builder.
      */
+    @SuppressWarnings("NullTernary")
     static Builder builder(Timed timed, String defaultName) {
         if (timed.longTask() && timed.value().isEmpty()) {
             // the user MUST name long task timers, we don't lump them in with regular

micrometer-core/src/main/java/io/micrometer/core/instrument/binder/grpc/AbstractMetricCollectingInterceptor.java

@@ -205,7 +205,7 @@ protected Function<Code, Timer> asTimerFunction(final Supplier<Timer.Builder> ti
         final Function<Code, Timer> cacheResolver = code -> cache.computeIfAbsent(code, creator);
         // Eager initialize
         for (final Code code : this.eagerInitializedCodes) {
-            cacheResolver.apply(code);
+            Timer ignored = cacheResolver.apply(code);
         }
         return cacheResolver;
     }

micrometer-core/src/main/java/io/micrometer/core/instrument/binder/jvm/JvmGcMetrics.java

@@ -339,33 +339,33 @@ enum GcGenerationAge {
 
         OLD, YOUNG, UNKNOWN;
 
-        private static final Map<String, GcGenerationAge> knownCollectors = new HashMap<String, GcGenerationAge>() {
-            {
-                put("ConcurrentMarkSweep", OLD);
-                put("Copy", YOUNG);
-                put("G1 Old Generation", OLD);
-                put("G1 Young Generation", YOUNG);
-                put("MarkSweepCompact", OLD);
-                put("PS MarkSweep", OLD);
-                put("PS Scavenge", YOUNG);
-                put("ParNew", YOUNG);
-                put("global", OLD);
-                put("scavenge", YOUNG);
-                put("partial gc", YOUNG);
-                put("global garbage collect", OLD);
-                put("Epsilon", OLD);
-                // GPGC (Azul's C4, see:
-                // https://docs.azul.com/prime/release-notes#prime_stream_22_12_0_0)
-                put("GPGC New", YOUNG); // old naming
-                put("GPGC Old", OLD); // old naming
-                put("GPGC New Cycles", YOUNG); // new naming
-                put("GPGC Old Cycles", OLD); // new naming
-                put("GPGC New Pauses", YOUNG); // new naming
-                put("GPGC Old Pauses", OLD); // new naming
-                put("ZGC Major Cycles", OLD); // do not include 'ZGC Major Pauses'; see
-                                              // gh-2872
-            }
-        };
+        private static final Map<String, GcGenerationAge> knownCollectors = new HashMap<>();
+
+        static {
+            knownCollectors.put("ConcurrentMarkSweep", OLD);
+            knownCollectors.put("Copy", YOUNG);
+            knownCollectors.put("G1 Old Generation", OLD);
+            knownCollectors.put("G1 Young Generation", YOUNG);
+            knownCollectors.put("MarkSweepCompact", OLD);
+            knownCollectors.put("PS MarkSweep", OLD);
+            knownCollectors.put("PS Scavenge", YOUNG);
+            knownCollectors.put("ParNew", YOUNG);
+            knownCollectors.put("global", OLD);
+            knownCollectors.put("scavenge", YOUNG);
+            knownCollectors.put("partial gc", YOUNG);
+            knownCollectors.put("global garbage collect", OLD);
+            knownCollectors.put("Epsilon", OLD);
+            // GPGC (Azul's C4, see:
+            // https://docs.azul.com/prime/release-notes#prime_stream_22_12_0_0)
+            knownCollectors.put("GPGC New", YOUNG); // old naming
+            knownCollectors.put("GPGC Old", OLD); // old naming
+            knownCollectors.put("GPGC New Cycles", YOUNG); // new naming
+            knownCollectors.put("GPGC Old Cycles", OLD); // new naming
+            knownCollectors.put("GPGC New Pauses", YOUNG); // new naming
+            knownCollectors.put("GPGC Old Pauses", OLD); // new naming
+            // do not include 'ZGC Major Pauses'; see gh-2872
+            knownCollectors.put("ZGC Major Cycles", OLD);
+        }
 
         static GcGenerationAge fromGcName(String gcName) {
             return knownCollectors.getOrDefault(gcName, UNKNOWN);

micrometer-core/src/main/java/io/micrometer/core/instrument/binder/system/FileDescriptorMetrics.java

@@ -123,7 +123,7 @@ private Method detectMethod(String name) {
         }
         try {
             // ensure the Bean we have is actually an instance of the interface
-            osBeanClass.cast(osBean);
+            Object ignored = osBeanClass.cast(osBean);
             return osBeanClass.getDeclaredMethod(name);
         }
         catch (ClassCastException | NoSuchMethodException | SecurityException e) {

micrometer-core/src/main/java/io/micrometer/core/instrument/binder/system/ProcessorMetrics.java

@@ -150,7 +150,7 @@ private Method detectMethod(String name) {
         }
         try {
             // ensure the Bean we have is actually an instance of the interface
-            operatingSystemBeanClass.cast(operatingSystemBean);
+            Object ignored = operatingSystemBeanClass.cast(operatingSystemBean);
             return operatingSystemBeanClass.getMethod(name);
         }
         catch (ClassCastException | NoSuchMethodException | SecurityException e) {

micrometer-core/src/main/java/io/micrometer/core/instrument/distribution/FixedBoundaryVictoriaMetricsHistogram.java

@@ -251,7 +251,7 @@ private void outputSummary(PrintStream printStream, double bucketScaling) {
         printStream.format("%14s %10s\n\n", "Bucket", "TotalCount");
 
         for (CountAtBucket bucket : nonZeroBuckets()) {
-            printStream.format(Locale.US, "%14.1f %10d\n", bucket.bucket() / bucketScaling, bucket.count());
+            printStream.format(Locale.US, "%14.1f %10f\n", bucket.bucket() / bucketScaling, bucket.count());
         }
 
         printStream.write('\n');

micrometer-core/src/test/java/io/micrometer/core/instrument/binder/jetty/InstrumentedQueuedThreadPoolTest.java

@@ -25,7 +25,7 @@
 import org.junit.jupiter.api.Test;
 
 import java.util.Arrays;
-import java.util.function.BiFunction;
+import java.util.function.BiConsumer;
 import java.util.stream.Collectors;
 
 import static org.assertj.core.api.Assertions.assertThat;
@@ -89,8 +89,8 @@ private void assertThatMetricsDoNotExist(MeterRegistry meterRegistry) {
     }
 
     private void assertThatMetrics(MeterRegistry meterRegistry,
-            BiFunction<Iterable<String>, ListAssert<String>, ListAssert<String>> assertFunction) {
-        assertFunction.apply(
+            BiConsumer<Iterable<String>, ListAssert<String>> assertConsumer) {
+        assertConsumer.accept(
                 Arrays.asList("jetty.threads.jobs", "jetty.threads.busy", "jetty.threads.idle",
                         "jetty.threads.config.max", "jetty.threads.config.min", "jetty.threads.current"),
                 assertThat(

micrometer-core/src/test/java/io/micrometer/core/instrument/binder/jvm/JvmMemoryMetricsTest.java

@@ -48,19 +48,19 @@ private void assertJvmMemoryMetrics(MeterRegistry registry, String area) {
         assertThat(memUsed.getId().getBaseUnit()).isEqualTo(BaseUnits.BYTES);
 
         Gauge memCommitted = registry.get("jvm.memory.committed").tags("area", area).gauge();
-        assertThat(memCommitted.value()).isNotNull();
+        assertThat(memCommitted.value()).isNotNaN();
         assertThat(memCommitted.getId().getBaseUnit()).isEqualTo(BaseUnits.BYTES);
 
         Gauge memMax = registry.get("jvm.memory.max").tags("area", area).gauge();
-        assertThat(memMax.value()).isNotNull();
+        assertThat(memMax.value()).isNotNaN();
         assertThat(memMax.getId().getBaseUnit()).isEqualTo(BaseUnits.BYTES);
     }
 
     private void assertJvmBufferMetrics(MeterRegistry registry, String bufferId) {
         assertThat(registry.get("jvm.buffer.count").tags("id", bufferId).gauge().value()).isGreaterThanOrEqualTo(0);
 
         Gauge memoryUsedDirect = registry.get("jvm.buffer.memory.used").tags("id", bufferId).gauge();
-        assertThat(memoryUsedDirect.value()).isNotNull();
+        assertThat(memoryUsedDirect.value()).isNotNaN();
         assertThat(memoryUsedDirect.getId().getBaseUnit()).isEqualTo(BaseUnits.BYTES);
 
         Gauge bufferTotal = registry.get("jvm.buffer.total.capacity").tags("id", bufferId).gauge();

micrometer-core/src/test/java/io/micrometer/core/instrument/distribution/TimeWindowMaxTest.java

@@ -71,8 +71,9 @@ void testLongPeriodOfInactivity() {
 
     @Test
     void throwsExceptionWhenRotateFrequency0() {
-        assertThatThrownBy(() -> new TimeWindowMax(clock, 0, 3)).isInstanceOf(IllegalArgumentException.class)
-            .withFailMessage("Rotate frequency must be a positive number");
+        assertThatThrownBy(() -> new TimeWindowMax(clock, 0, 3))
+            .withFailMessage("Rotate frequency must be a positive number")
+            .isInstanceOf(IllegalArgumentException.class);
     }
 
 }

micrometer-core/src/test/java/io/micrometer/core/instrument/step/StepMeterRegistryTest.java

@@ -657,7 +657,7 @@ protected void publish() {
                 prePublishAction.run();
             }
             publishCount.incrementAndGet();
-            getMeters().stream()
+            List<Meter> ignored = getMeters().stream()
                 .map(meter -> meter.match(g -> null, this::publishCounter, this::publishTimer, this::publishSummary,
                         null, tg -> null, this::publishFunctionCounter, this::publishFunctionTimer, m -> null))
                 .collect(Collectors.toList());

micrometer-observation-test/src/main/java/io/micrometer/observation/tck/TestObservationRegistry.java

@@ -122,7 +122,7 @@ public boolean equals(Object o) {
             if (this == o) {
                 return true;
             }
-            if (o == null || getClass() != o.getClass()) {
+            if (!(o instanceof TestObservationContext)) {
                 return false;
             }
             TestObservationContext that = (TestObservationContext) o;

micrometer-observation-test/src/main/java/io/micrometer/observation/tck/TestObservationRegistryAssert.java

@@ -332,7 +332,7 @@ public TestObservationRegistryAssert hasNumberOfObservationsWithNameEqualToIgnor
      */
     public TestObservationRegistryAssert hasAnObservationWithAKeyValue(String key, String value) {
         isNotNull();
-        this.actual.getContexts()
+        KeyValue ignored = this.actual.getContexts()
             .stream()
             .flatMap(f -> f.getContext().getAllKeyValues().stream())
             .filter(keyValue -> keyValue.getKey().equals(key) && keyValue.getValue().equals(value))
@@ -381,7 +381,7 @@ public TestObservationRegistryAssert hasAnObservationWithAKeyValue(KeyValue keyV
      */
     public TestObservationRegistryAssert hasAnObservationWithAKeyName(String key) {
         isNotNull();
-        this.actual.getContexts()
+        KeyValue ignored = this.actual.getContexts()
             .stream()
             .flatMap(f -> f.getContext().getAllKeyValues().stream())
             .filter(keyValue -> keyValue.getKey().equals(key))

micrometer-test/src/test/java/io/micrometer/core/instrument/binder/cache/CaffeineCacheMetricsCompatibilityTest.java

@@ -41,6 +41,7 @@ public CacheMeterBinder<LoadingCache<String, String>> binder() {
         return new CaffeineCacheMetrics<>(cache, "mycache", emptyList());
     }
 
+    @SuppressWarnings("CheckReturnValue")
     @Override
     public void put(String key, String value) {
         synchronized (this) {

samples/micrometer-samples-core/src/main/java/io/micrometer/core/samples/utils/SampleRegistries.java

@@ -122,7 +122,7 @@ public String get(String k) {
                 os.close();
             });
 
-            new Thread(server::start).run();
+            new Thread(server::start).start();
         }
         catch (IOException e) {
             throw new RuntimeException(e);