Add @CanIgnoreReturnValue annotations

caffeine/build.gradle

@@ -122,6 +122,7 @@ tasks.named('compileJava').configure {
   dependsOn generateLocalCaches, generateNodes
   finalizedBy compileCodeGenJava
   options.errorprone.disable('CheckReturnValue')
+  options.errorprone.error('CanIgnoreReturnValueSuggester')
 }
 tasks.named('compileTestJava').configure {
   dependsOn jar, compileCodeGenJava

caffeine/src/main/java/com/github/benmanes/caffeine/cache/Caffeine.java

@@ -46,6 +46,7 @@
 import com.github.benmanes.caffeine.cache.stats.CacheStats;
 import com.github.benmanes.caffeine.cache.stats.ConcurrentStatsCounter;
 import com.github.benmanes.caffeine.cache.stats.StatsCounter;
+import com.google.errorprone.annotations.CanIgnoreReturnValue;
 import com.google.errorprone.annotations.FormatMethod;
 
 /**
@@ -291,6 +292,7 @@ public static Caffeine<Object, Object> from(String spec) {
    * @throws IllegalArgumentException if {@code initialCapacity} is negative
    * @throws IllegalStateException if an initial capacity was already set
    */
+  @CanIgnoreReturnValue
   public Caffeine<K, V> initialCapacity(@NonNegative int initialCapacity) {
     requireState(this.initialCapacity == UNSET_INT,
         "initial capacity was already set to %s", this.initialCapacity);
@@ -324,6 +326,7 @@ int getInitialCapacity() {
    * @return this {@code Caffeine} instance (for chaining)
    * @throws NullPointerException if the specified executor is null
    */
+  @CanIgnoreReturnValue
   public Caffeine<K, V> executor(Executor executor) {
     requireState(this.executor == null, "executor was already set to %s", this.executor);
     this.executor = requireNonNull(executor);
@@ -355,6 +358,7 @@ Executor getExecutor() {
    * @return this {@code Caffeine} instance (for chaining)
    * @throws NullPointerException if the specified scheduler is null
    */
+  @CanIgnoreReturnValue
   public Caffeine<K, V> scheduler(Scheduler scheduler) {
     requireState(this.scheduler == null, "scheduler was already set to %s", this.scheduler);
     this.scheduler = requireNonNull(scheduler);
@@ -389,6 +393,7 @@ Scheduler getScheduler() {
    * @throws IllegalArgumentException if {@code size} is negative
    * @throws IllegalStateException if a maximum size or weight was already set
    */
+  @CanIgnoreReturnValue
   public Caffeine<K, V> maximumSize(@NonNegative long maximumSize) {
     requireState(this.maximumSize == UNSET_INT,
         "maximum size was already set to %s", this.maximumSize);
@@ -425,6 +430,7 @@ public Caffeine<K, V> maximumSize(@NonNegative long maximumSize) {
    * @throws IllegalArgumentException if {@code maximumWeight} is negative
    * @throws IllegalStateException if a maximum weight or size was already set
    */
+  @CanIgnoreReturnValue
   public Caffeine<K, V> maximumWeight(@NonNegative long maximumWeight) {
     requireState(this.maximumWeight == UNSET_INT,
         "maximum weight was already set to %s", this.maximumWeight);
@@ -517,6 +523,7 @@ <K1 extends K, V1 extends V> Weigher<K1, V1> getWeigher(boolean isAsync) {
    * @return this {@code Caffeine} instance (for chaining)
    * @throws IllegalStateException if the key strength was already set
    */
+  @CanIgnoreReturnValue
   public Caffeine<K, V> weakKeys() {
     requireState(keyStrength == null, "Key strength was already set to %s", keyStrength);
     keyStrength = Strength.WEAK;
@@ -546,6 +553,7 @@ boolean isStrongKeys() {
    * @return this {@code Caffeine} instance (for chaining)
    * @throws IllegalStateException if the value strength was already set
    */
+  @CanIgnoreReturnValue
   public Caffeine<K, V> weakValues() {
     requireState(valueStrength == null, "Value strength was already set to %s", valueStrength);
     valueStrength = Strength.WEAK;
@@ -582,6 +590,7 @@ boolean isWeakValues() {
    * @return this {@code Caffeine} instance (for chaining)
    * @throws IllegalStateException if the value strength was already set
    */
+  @CanIgnoreReturnValue
   public Caffeine<K, V> softValues() {
     requireState(valueStrength == null, "Value strength was already set to %s", valueStrength);
     valueStrength = Strength.SOFT;
@@ -604,6 +613,7 @@ public Caffeine<K, V> softValues() {
    * @throws IllegalStateException if the time to live or variable expiration was already set
    * @throws ArithmeticException for durations greater than +/- approximately 292 years
    */
+  @CanIgnoreReturnValue
   public Caffeine<K, V> expireAfterWrite(Duration duration) {
     return expireAfterWrite(saturatedToNanos(duration), TimeUnit.NANOSECONDS);
   }
@@ -627,6 +637,7 @@ public Caffeine<K, V> expireAfterWrite(Duration duration) {
    * @throws IllegalArgumentException if {@code duration} is negative
    * @throws IllegalStateException if the time to live or variable expiration was already set
    */
+  @CanIgnoreReturnValue
   public Caffeine<K, V> expireAfterWrite(@NonNegative long duration, TimeUnit unit) {
     requireState(expireAfterWriteNanos == UNSET_INT,
         "expireAfterWrite was already set to %s ns", expireAfterWriteNanos);
@@ -663,6 +674,7 @@ boolean expiresAfterWrite() {
    * @throws IllegalStateException if the time to idle or variable expiration was already set
    * @throws ArithmeticException for durations greater than +/- approximately 292 years
    */
+  @CanIgnoreReturnValue
   public Caffeine<K, V> expireAfterAccess(Duration duration) {
     return expireAfterAccess(saturatedToNanos(duration), TimeUnit.NANOSECONDS);
   }
@@ -689,6 +701,7 @@ public Caffeine<K, V> expireAfterAccess(Duration duration) {
    * @throws IllegalArgumentException if {@code duration} is negative
    * @throws IllegalStateException if the time to idle or variable expiration was already set
    */
+  @CanIgnoreReturnValue
   public Caffeine<K, V> expireAfterAccess(@NonNegative long duration, TimeUnit unit) {
     requireState(expireAfterAccessNanos == UNSET_INT,
         "expireAfterAccess was already set to %s ns", expireAfterAccessNanos);
@@ -779,6 +792,7 @@ boolean expiresVariable() {
    * @throws IllegalStateException if the refresh interval was already set
    * @throws ArithmeticException for durations greater than +/- approximately 292 years
    */
+  @CanIgnoreReturnValue
   public Caffeine<K, V> refreshAfterWrite(Duration duration) {
     return refreshAfterWrite(saturatedToNanos(duration), TimeUnit.NANOSECONDS);
   }
@@ -806,6 +820,7 @@ public Caffeine<K, V> refreshAfterWrite(Duration duration) {
    * @throws IllegalArgumentException if {@code duration} is zero or negative
    * @throws IllegalStateException if the refresh interval was already set
    */
+  @CanIgnoreReturnValue
   public Caffeine<K, V> refreshAfterWrite(@NonNegative long duration, TimeUnit unit) {
     requireNonNull(unit);
     requireState(refreshAfterWriteNanos == UNSET_INT,
@@ -835,6 +850,7 @@ boolean refreshAfterWrite() {
    * @throws IllegalStateException if a ticker was already set
    * @throws NullPointerException if the specified ticker is null
    */
+  @CanIgnoreReturnValue
   public Caffeine<K, V> ticker(Ticker ticker) {
     requireState(this.ticker == null, "Ticker was already set to %s", this.ticker);
     this.ticker = requireNonNull(ticker);
@@ -961,6 +977,7 @@ public <K1 extends K, V1 extends V> Caffeine<K1, V1> removalListener(
    *
    * @return this {@code Caffeine} instance (for chaining)
    */
+  @CanIgnoreReturnValue
   public Caffeine<K, V> recordStats() {
     requireState(this.statsCounterSupplier == null, "Statistics recording was already set");
     statsCounterSupplier = ENABLED_STATS_COUNTER_SUPPLIER;
@@ -977,6 +994,7 @@ public Caffeine<K, V> recordStats() {
    * @param statsCounterSupplier a supplier instance that returns a new {@link StatsCounter}
    * @return this {@code Caffeine} instance (for chaining)
    */
+  @CanIgnoreReturnValue
   public Caffeine<K, V> recordStats(Supplier<? extends StatsCounter> statsCounterSupplier) {
     requireState(this.statsCounterSupplier == null, "Statistics recording was already set");
     requireNonNull(statsCounterSupplier);

examples/write-behind-rxjava/src/main/java/com/github/benmanes/caffeine/examples/writebehind/rxjava/WriteBehindCacheWriter.java

@@ -27,6 +27,8 @@
 
 import io.reactivex.subjects.PublishSubject;
 
+import com.google.errorprone.annotations.CanIgnoreReturnValue;
+
 /**
  * This class allows a cache to have "write-behind" semantics. The passed in writeAction will only
  * be called every 'bufferTime' time with a Map containing the keys and the values that have been
@@ -67,18 +69,21 @@ public static final class Builder<K, V> {
      * The duration that the calls to the cache should be buffered before calling the
      * <code>writeAction</code>.
      */
+    @CanIgnoreReturnValue
     public Builder<K, V> bufferTime(long duration, TimeUnit unit) {
       this.bufferTimeNanos = TimeUnit.NANOSECONDS.convert(duration, unit);
       return this;
     }
 
     /** The callback to perform the writing to the database or repository. */
+    @CanIgnoreReturnValue
     public Builder<K, V> writeAction(Consumer<Map<K, V>> writeAction) {
       this.writeAction = requireNonNull(writeAction);
       return this;
     }
 
     /** The action that decides which value to take in case a key was updated multiple times. */
+    @CanIgnoreReturnValue
     public Builder<K, V> coalesce(BinaryOperator<V> coalescer) {
       this.coalescer = requireNonNull(coalescer);
       return this;

guava/src/main/java/com/github/benmanes/caffeine/guava/CaffeinatedGuavaCache.java

@@ -40,6 +40,7 @@
 import com.google.common.collect.ImmutableMap;
 import com.google.common.util.concurrent.ExecutionError;
 import com.google.common.util.concurrent.UncheckedExecutionException;
+import com.google.errorprone.annotations.CanIgnoreReturnValue;
 
 /**
  * A Caffeine-backed cache through a Guava facade.
@@ -240,6 +241,7 @@ static final class CacheLoaderException extends RuntimeException {
     CacheLoaderException(Exception e) {
       super(e);
     }
+    @CanIgnoreReturnValue
     @SuppressWarnings({"lgtm [java/non-sync-override]", "UnsynchronizedOverridesSynchronized"})
     @Override public Throwable fillInStackTrace() {
       return this;

simulator/src/main/java/com/github/benmanes/caffeine/cache/simulator/policy/PolicyStats.java

@@ -36,6 +36,7 @@
 import com.google.auto.value.AutoValue.CopyAnnotations;
 import com.google.common.base.Stopwatch;
 import com.google.common.collect.ImmutableSet;
+import com.google.errorprone.annotations.CanIgnoreReturnValue;
 
 /**
  * Statistics gathered by a policy execution. A policy can extend this class as a convenient way to
@@ -318,6 +319,7 @@ public abstract static class Builder {
       public abstract ImmutableSet.Builder<Characteristic> characteristicsBuilder();
       public abstract Metric build();
 
+      @CanIgnoreReturnValue
       public final Builder addCharacteristic(Characteristic characteristic) {
         characteristicsBuilder().add(characteristic);
         return this;