[7.x] Enable BooleanNegation checkstyle rule always

buildSrc/src/integTest/groovy/org/elasticsearch/gradle/TestClustersPluginFuncTest.groovy

@@ -125,7 +125,7 @@ class TestClustersPluginFuncTest extends AbstractGradleFuncTest {
     }
 
     boolean assertNoCustomDistro(String clusterName) {
-        assert !customDistroFolder(clusterName).exists()
+        assert customDistroFolder(clusterName).exists() == false
         true
     }
 

buildSrc/src/main/resources/checkstyle.xml

@@ -124,17 +124,17 @@
     </module>
 
     <!-- Forbid using '!' for logical negations in favour of checking against 'false' explicitly. -->
-    <!-- This is disabled for now because there are many violations, hence the rule is reporting at the "warning" severity. -->
-    <!--
+    <!-- This is only reported in the IDE for now because there are many violations -->
     <module name="DescendantToken">
-      <property name="id" value="BooleanNegation" />
-      <property name="tokens" value="EXPR"/>
-      <property name="limitedTokens" value="LNOT"/>
-      <property name="maximumNumber" value="0"/>
-      <property name="maximumDepth" value="1"/>
-      <message key="descendant.token.max" value="Do not negate boolean expressions with '!', but check explicitly with '== false' as it is more explicit"/>
+        <property name="id" value="BooleanNegation" />
+        <property name="tokens" value="EXPR"/>
+        <property name="limitedTokens" value="LNOT"/>
+        <property name="maximumNumber" value="0"/>
+        <property name="maximumDepth" value="2"/>
+        <message
+            key="descendant.token.max"
+            value="Do not negate boolean expressions with '!', but check explicitly with '== false' as it is more explicit"/>
     </module>
-    -->
 
   </module>
 </module>

buildSrc/src/main/resources/checkstyle_ide_fragment.xml

@@ -8,18 +8,6 @@
 <!-- Checkstyle config by the `:configureIdeCheckstyle` task.           -->
 
 <module name="IdeFragment">
-    <!-- Forbid using '!' for logical negations in favour of checking against 'false' explicitly. -->
-    <!-- This is only reported in the IDE for now because there are many violations -->
-    <module name="DescendantToken">
-        <property name="id" value="BooleanNegation" />
-        <property name="tokens" value="EXPR"/>
-        <property name="limitedTokens" value="LNOT"/>
-        <property name="maximumNumber" value="0"/>
-        <property name="maximumDepth" value="2"/>
-        <message
-            key="descendant.token.max"
-            value="Do not negate boolean expressions with '!', but check explicitly with '== false' as it is more explicit"/>
-    </module>
 
     <!-- See CONTRIBUTING.md for our guidelines on Javadoc -->
 

client/benchmark/src/main/java/org/elasticsearch/client/benchmark/transport/TransportClientBenchmark.java

@@ -82,7 +82,7 @@ public boolean bulkIndex(List<String> bulkData) {
             } catch (ExecutionException e) {
                 throw new ElasticsearchException(e);
             }
-            return !bulkResponse.hasFailures();
+            return bulkResponse.hasFailures() == false;
         }
     }
 

client/rest-high-level/src/test/java/org/elasticsearch/client/indices/GetMappingsResponseTests.java

@@ -55,7 +55,7 @@ private static void assertEqualInstances(GetMappingsResponse expected, GetMappin
     }
 
     private Predicate<String> randomFieldsExcludeFilter() {
-        return field -> !field.equals(MAPPINGS.getPreferredName());
+        return field -> field.equals(MAPPINGS.getPreferredName()) == false;
     }
 
     public static MappingMetadata randomMappingMetadata() {

client/rest-high-level/src/test/java/org/elasticsearch/client/ml/EvaluateDataFrameRequestTests.java

@@ -60,7 +60,7 @@ protected boolean supportsUnknownFields() {
     @Override
     protected Predicate<String> getRandomFieldsExcludeFilter() {
         // allow unknown fields in root only
-        return field -> !field.isEmpty();
+        return field -> field.isEmpty() == false;
     }
 
     @Override

modules/analysis-common/src/main/java/org/elasticsearch/analysis/common/StandardHtmlStripAnalyzer.java

@@ -38,7 +38,7 @@ public StandardHtmlStripAnalyzer() {
     protected TokenStreamComponents createComponents(final String fieldName) {
         final Tokenizer src = new StandardTokenizer();
         TokenStream tok = new LowerCaseFilter(src);
-        if (!stopwords.isEmpty()) {
+        if (stopwords.isEmpty() == false) {
             tok = new StopFilter(tok, stopwords);
         }
         return new TokenStreamComponents(src, tok);

modules/lang-painless/src/doc/java/org/elasticsearch/painless/JavadocExtractor.java

@@ -179,7 +179,7 @@ public static MethodSignature fromDeclaration(MethodDeclaration declaration) {
         @Override
         public boolean equals(Object o) {
             if (this == o) return true;
-            if (!(o instanceof MethodSignature)) return false;
+            if ((o instanceof MethodSignature) == false) return false;
             MethodSignature that = (MethodSignature) o;
             return Objects.equals(name, that.name) &&
                 Objects.equals(parameterTypes, that.parameterTypes);

plugins/analysis-phonetic/src/main/java/org/elasticsearch/index/analysis/phonetic/Nysiis.java

@@ -141,7 +141,7 @@ private static char[] transcodeRemaining(final char prev, final char curr, final
         }
 
         // 5. H -> If previous or next is a non vowel, previous.
-        if (curr == 'H' && (!isVowel(prev) || !isVowel(next))) {
+        if (curr == 'H' && (isVowel(prev) == false || isVowel(next) == false)) {
             return new char[]{prev};
         }
 
@@ -192,7 +192,7 @@ public Nysiis(final boolean strict) {
      */
     @Override
     public Object encode(Object obj) throws EncoderException {
-        if (!(obj instanceof String)) {
+        if ((obj instanceof String) == false) {
             throw new EncoderException("Parameter supplied to Nysiis encode is not of type java.lang.String");
         }
         return this.nysiis((String) obj);

qa/smoke-test-http/src/test/java/org/elasticsearch/http/ContextAndHeaderTransportIT.java

@@ -257,7 +257,7 @@ private void assertGetRequestsContainHeaders(String index) {
         assertThat(getRequests, hasSize(greaterThan(0)));
 
         for (RequestAndHeaders request : getRequests) {
-            if (!((GetRequest)request.request).index().equals(index)) {
+            if (((GetRequest)request.request).index().equals(index) == false) {
                 continue;
             }
             assertRequestContainsHeader(request.request, request.headers);

server/src/internalClusterTest/java/org/elasticsearch/search/aggregations/pipeline/MovAvgIT.java

@@ -1249,13 +1249,13 @@ public void testPredictWithNonEmptyBuckets() throws Exception {
     }
 
     private void assertValidIterators(Iterator expectedBucketIter, Iterator expectedCountsIter, Iterator expectedValuesIter) {
-        if (!expectedBucketIter.hasNext()) {
+        if (expectedBucketIter.hasNext() == false) {
             fail("`expectedBucketIter` iterator ended before `actual` iterator, size mismatch");
         }
-        if (!expectedCountsIter.hasNext()) {
+        if (expectedCountsIter.hasNext() == false) {
             fail("`expectedCountsIter` iterator ended before `actual` iterator, size mismatch");
         }
-        if (!expectedValuesIter.hasNext()) {
+        if (expectedValuesIter.hasNext() == false) {
             fail("`expectedValuesIter` iterator ended before `actual` iterator, size mismatch");
         }
     }

server/src/main/java/org/elasticsearch/action/admin/cluster/snapshots/create/CreateSnapshotRequest.java

@@ -430,7 +430,7 @@ public CreateSnapshotRequest source(Map<String, Object> source) {
             } else if (name.equals("partial")) {
                 partial(nodeBooleanValue(entry.getValue(), "partial"));
             } else if (name.equals("settings")) {
-                if (!(entry.getValue() instanceof Map)) {
+                if ((entry.getValue() instanceof Map) == false) {
                     throw new IllegalArgumentException("malformed settings section, should indices an inner object");
                 }
                 settings((Map<String, Object>) entry.getValue());

server/src/main/java/org/elasticsearch/action/admin/cluster/snapshots/restore/RestoreSnapshotRequest.java

@@ -487,7 +487,7 @@ public RestoreSnapshotRequest source(Map<String, Object> source) {
             } else if (name.equals("partial")) {
                 partial(nodeBooleanValue(entry.getValue(), "partial"));
             } else if (name.equals("settings")) {
-                if (!(entry.getValue() instanceof Map)) {
+                if ((entry.getValue() instanceof Map) == false) {
                     throw new IllegalArgumentException("malformed settings section");
                 }
                 DEPRECATION_LOGGER.deprecate(DeprecationCategory.API, "RestoreSnapshotRequest#settings",

server/src/main/java/org/elasticsearch/action/admin/indices/create/CreateIndexRequest.java

@@ -265,7 +265,7 @@ public CreateIndexRequest mapping(String type, Map<String, ?> source) {
             throw new IllegalStateException("mappings for type \"" + type + "\" were already defined");
         }
         // wrap it in a type map if its not
-        if (source.size() != 1 || !source.containsKey(type)) {
+        if (source.size() != 1 || source.containsKey(type) == false) {
             source = MapBuilder.<String, Object>newMapBuilder().put(type, source).map();
         }
         try {

server/src/main/java/org/elasticsearch/action/admin/indices/exists/types/TransportTypesExistsAction.java

@@ -49,7 +49,7 @@ protected void masterOperation(final TypesExistsRequest request, final ClusterSt
         }
 
         for (String concreteIndex : concreteIndices) {
-            if (!state.metadata().hasConcreteIndex(concreteIndex)) {
+            if (state.metadata().hasConcreteIndex(concreteIndex) == false) {
                 listener.onResponse(new TypesExistsResponse(false));
                 return;
             }

server/src/main/java/org/elasticsearch/action/admin/indices/get/GetIndexResponse.java

@@ -412,7 +412,7 @@ public static GetIndexResponse fromXContent(XContentParser parser) throws IOExce
         ensureExpectedToken(Token.START_OBJECT, parser.currentToken(), parser);
         parser.nextToken();
 
-        while (!parser.isClosed()) {
+        while (parser.isClosed() == false) {
             if (parser.currentToken() == Token.START_OBJECT) {
                 // we assume this is an index entry
                 String indexName = parser.currentName();

server/src/main/java/org/elasticsearch/action/admin/indices/mapping/get/TransportGetFieldMappingsIndexAction.java

@@ -103,7 +103,7 @@ protected GetFieldMappingsResponse shardOperation(final GetFieldMappingsIndexReq
         for (String type : typeIntersection) {
             DocumentMapper documentMapper = indexService.mapperService().documentMapper(type);
             Map<String, FieldMappingMetadata> fieldMapping = findFieldMappingsByType(fieldPredicate, documentMapper, request);
-            if (!fieldMapping.isEmpty()) {
+            if (fieldMapping.isEmpty() == false) {
                 typeMappings.put(type, fieldMapping);
             }
         }

server/src/main/java/org/elasticsearch/action/admin/indices/template/put/PutIndexTemplateRequest.java

@@ -278,7 +278,7 @@ public PutIndexTemplateRequest mapping(String type, BytesReference source, XCont
      */
     public PutIndexTemplateRequest mapping(String type, Map<String, Object> source) {
         // wrap it in a type map if its not
-        if (source.size() != 1 || !source.containsKey(type)) {
+        if (source.size() != 1 || source.containsKey(type) == false) {
             source = MapBuilder.<String, Object>newMapBuilder().put(type, source).map();
         }
         try {

server/src/main/java/org/elasticsearch/action/support/AutoCreateIndex.java

@@ -46,7 +46,7 @@ public AutoCreateIndex(Settings settings,
                            IndexNameExpressionResolver resolver,
                            SystemIndices systemIndices) {
         this.resolver = resolver;
-        dynamicMappingDisabled = !MapperService.INDEX_MAPPER_DYNAMIC_SETTING.get(settings);
+        dynamicMappingDisabled = MapperService.INDEX_MAPPER_DYNAMIC_SETTING.get(settings) == false;
         this.systemIndices = systemIndices;
         this.autoCreate = AUTO_CREATE_INDEX_SETTING.get(settings);
         clusterSettings.addSettingsUpdateConsumer(AUTO_CREATE_INDEX_SETTING, this::setAutoCreate);

server/src/main/java/org/elasticsearch/client/transport/TransportClientNodesService.java

@@ -172,7 +172,7 @@ public TransportClientNodesService addTransportAddresses(TransportAddress... tra
                         break;
                     }
                 }
-                if (!found) {
+                if (found == false) {
                     filtered.add(transportAddress);
                 }
             }
@@ -199,7 +199,7 @@ public TransportClientNodesService removeTransportAddress(TransportAddress trans
             }
             List<DiscoveryNode> listNodesBuilder = new ArrayList<>();
             for (DiscoveryNode otherNode : listedNodes) {
-                if (!otherNode.getAddress().equals(transportAddress)) {
+                if (otherNode.getAddress().equals(transportAddress) == false) {
                     listNodesBuilder.add(otherNode);
                 } else {
                     logger.debug("removing address [{}] from listed nodes", otherNode);
@@ -208,7 +208,7 @@ public TransportClientNodesService removeTransportAddress(TransportAddress trans
             listedNodes = Collections.unmodifiableList(listNodesBuilder);
             List<DiscoveryNode> nodesBuilder = new ArrayList<>();
             for (DiscoveryNode otherNode : nodes) {
-                if (!otherNode.getAddress().equals(transportAddress)) {
+                if (otherNode.getAddress().equals(transportAddress) == false) {
                     nodesBuilder.add(otherNode);
                 } else {
                     logger.debug("disconnecting from node with address [{}]", otherNode);
@@ -359,7 +359,7 @@ public void sample() {
         List<DiscoveryNode> establishNodeConnections(Set<DiscoveryNode> nodes) {
             for (Iterator<DiscoveryNode> it = nodes.iterator(); it.hasNext(); ) {
                 DiscoveryNode node = it.next();
-                if (!transportService.nodeConnected(node)) {
+                if (transportService.nodeConnected(node) == false) {
                     try {
                         logger.trace("connecting to node [{}]", node);
                         transportService.connectToNode(node);
@@ -379,7 +379,7 @@ class ScheduledNodeSampler implements Runnable {
         public void run() {
             try {
                 nodesSampler.sample();
-                if (!closed) {
+                if (closed == false) {
                     nodesSamplerCancellable = threadPool.schedule(this, nodesSamplerInterval, ThreadPool.Names.GENERIC);
                 }
             } catch (Exception e) {
@@ -407,7 +407,7 @@ public LivenessResponse read(StreamInput in) throws IOException {
                         TransportRequestOptions.of(pingTimeout, TransportRequestOptions.Type.STATE),
                         handler);
                     final LivenessResponse livenessResponse = handler.txGet();
-                    if (!ignoreClusterName && !clusterName.equals(livenessResponse.getClusterName())) {
+                    if (ignoreClusterName == false && clusterName.equals(livenessResponse.getClusterName()) == false) {
                         logger.warn("node {} not part of the cluster {}, ignoring...", listedNode, clusterName);
                         newFilteredNodes.add(listedNode);
                     } else {
@@ -536,7 +536,7 @@ public void handleException(TransportException e) {
             HashSet<DiscoveryNode> newNodes = new HashSet<>();
             HashSet<DiscoveryNode> newFilteredNodes = new HashSet<>();
             for (Map.Entry<DiscoveryNode, ClusterStateResponse> entry : clusterStateResponses.entrySet()) {
-                if (!ignoreClusterName && !clusterName.equals(entry.getValue().getClusterName())) {
+                if (ignoreClusterName == false && clusterName.equals(entry.getValue().getClusterName()) == false) {
                     logger.warn("node {} not part of the cluster {}, ignoring...",
                             entry.getValue().getState().nodes().getLocalNode(), clusterName);
                     newFilteredNodes.add(entry.getKey());

server/src/main/java/org/elasticsearch/cluster/metadata/IndexTemplateMetadata.java

@@ -413,7 +413,7 @@ private static void toInnerXContent(IndexTemplateMetadata indexTemplateMetadata,
                 if (includeTypeName == false) {
                     Map<String, Object> documentMapping = null;
                     for (ObjectObjectCursor<String, CompressedXContent> cursor : indexTemplateMetadata.mappings()) {
-                        if (!cursor.key.equals(MapperService.DEFAULT_MAPPING)) {
+                        if (cursor.key.equals(MapperService.DEFAULT_MAPPING) == false) {
                             assert documentMapping == null;
                             Map<String, Object> mapping = XContentHelper.convertToMap(cursor.value.uncompressed(), true).v2();
                             documentMapping = reduceMapping(cursor.key, mapping);

server/src/main/java/org/elasticsearch/cluster/metadata/Metadata.java

@@ -394,7 +394,7 @@ public boolean hasAliases(final String[] aliases, String[] concreteIndices) {
                     filteredValues.add(value);
                 }
             }
-            if (!filteredValues.isEmpty()) {
+            if (filteredValues.isEmpty() == false) {
                 return true;
             }
         }
@@ -435,7 +435,7 @@ public ImmutableOpenMap<String, ImmutableOpenMap<String, MappingMetadata>> findM
                         filteredMappings.put(cursor.key, filterFields(cursor.value, fieldPredicate));
                     }
                 }
-                if (!filteredMappings.isEmpty()) {
+                if (filteredMappings.isEmpty() == false) {
                     indexMapBuilder.put(index, filteredMappings.build());
                 }
             }
@@ -616,7 +616,7 @@ public String resolveWriteIndexRouting(@Nullable String routing, String aliasOrI
                     + aliasMd.getIndexRouting() + "] that resolved to several routing values, rejecting operation");
             }
             if (routing != null) {
-                if (!routing.equals(aliasMd.indexRouting())) {
+                if (routing.equals(aliasMd.indexRouting()) == false) {
                     throw new IllegalArgumentException("Alias [" + aliasOrIndex + "] has index routing associated with it ["
                         + aliasMd.indexRouting() + "], and was provided with routing value [" + routing + "], rejecting operation");
                 }

server/src/main/java/org/elasticsearch/cluster/metadata/MetadataMappingService.java

@@ -171,7 +171,7 @@ private boolean refreshIndexMapping(IndexService indexService, IndexMetadata.Bui
                                                        mapperService.documentMapper(MapperService.DEFAULT_MAPPING))) {
                 if (mapper != null) {
                     final String type = mapper.type();
-                    if (!mapper.mappingSource().equals(builder.mapping(type).source())) {
+                    if (mapper.mappingSource().equals(builder.mapping(type).source()) == false) {
                         updatedTypes.add(type);
                     }
                 }

server/src/main/java/org/elasticsearch/common/path/PathTrie.java

@@ -245,7 +245,7 @@ public T retrieve(String[] path, int index, Map<String, String> params, TrieMatc
             }
 
             T nodeValue = node.retrieve(path, index + 1, params, trieMatchingMode);
-            if (nodeValue == null && !usedWildcard && trieMatchingMode != TrieMatchingMode.EXPLICIT_NODES_ONLY) {
+            if (nodeValue == null && usedWildcard == false && trieMatchingMode != TrieMatchingMode.EXPLICIT_NODES_ONLY) {
                 node = children.get(wildcard);
                 if (node != null) {
                     put(params, node, token);

server/src/main/java/org/elasticsearch/common/util/set/Sets.java

@@ -88,7 +88,7 @@ public static <T> Set<T> difference(Set<T> left, Set<T> right) {
     public static <T> SortedSet<T> sortedDifference(Set<T> left, Set<T> right) {
         Objects.requireNonNull(left);
         Objects.requireNonNull(right);
-        return left.stream().filter(k -> !right.contains(k)).collect(new SortedSetCollector<>());
+        return left.stream().filter(k -> right.contains(k) == false).collect(new SortedSetCollector<>());
     }
 
     private static class SortedSetCollector<T> implements Collector<T, SortedSet<T>, SortedSet<T>> {

server/src/main/java/org/elasticsearch/discovery/zen/ElectMasterService.java

@@ -194,17 +194,17 @@ private List<DiscoveryNode> sortedMasterNodes(Iterable<DiscoveryNode> nodes) {
             return null;
         }
         // clean non master nodes
-        possibleNodes.removeIf(node -> !node.isMasterNode());
+        possibleNodes.removeIf(node -> node.isMasterNode() == false);
         CollectionUtil.introSort(possibleNodes, ElectMasterService::compareNodes);
         return possibleNodes;
     }
 
     /** master nodes go before other nodes, with a secondary sort by id **/
      private static int compareNodes(DiscoveryNode o1, DiscoveryNode o2) {
-        if (o1.isMasterNode() && !o2.isMasterNode()) {
+        if (o1.isMasterNode() && o2.isMasterNode() == false) {
             return -1;
         }
-        if (!o1.isMasterNode() && o2.isMasterNode()) {
+        if (o1.isMasterNode() == false && o2.isMasterNode()) {
             return 1;
         }
         return o1.getId().compareTo(o2.getId());