Don't emit deprecation issue for compatible date format patterns (#127418)

Author: mark-vieira

docs/changelog/127418.yaml

@@ -0,0 +1,5 @@
+pr: 127418
+summary: Don't emit deprecation issue for compatible date format patterns
+area: Infra/Core
+type: bug
+issues: []

server/src/main/java/org/elasticsearch/common/time/DateUtils.java

@@ -20,6 +20,7 @@
 import java.time.Instant;
 import java.time.ZoneId;
 import java.time.ZonedDateTime;
+import java.util.Arrays;
 import java.util.Collections;
 import java.util.HashMap;
 import java.util.Map;
@@ -481,6 +482,6 @@ static void checkTextualDateFormats(String format) {
     }
 
     public static boolean containsCompatOnlyDateFormat(String format) {
-        return LEGACY_DATE_FORMAT_MATCHER.test(format);
+        return LEGACY_DATE_FORMAT_MATCHER.test(format) && Arrays.stream(FormatNames.values()).noneMatch(f -> f.getName().equals(format));
     }
 }

x-pack/plugin/deprecation/src/test/java/org/elasticsearch/xpack/deprecation/IndexDeprecationCheckerTests.java

@@ -21,6 +21,7 @@
 import org.elasticsearch.cluster.metadata.MetadataIndexStateService;
 import org.elasticsearch.common.collect.ImmutableOpenMap;
 import org.elasticsearch.common.settings.Settings;
+import org.elasticsearch.common.time.FormatNames;
 import org.elasticsearch.core.TimeValue;
 import org.elasticsearch.index.IndexMode;
 import org.elasticsearch.index.IndexSettings;
@@ -36,6 +37,7 @@
 
 import java.util.ArrayList;
 import java.util.List;
+import java.util.Locale;
 import java.util.Map;
 
 import static java.util.Collections.singletonList;
@@ -234,6 +236,45 @@ public void testOldIndicesWithIncompatibleDateFormatsCheck() {
         assertEquals(singletonList(expected), issues);
     }
 
+    public void testOldIndicesWithCompatibleDateFormatter() {
+        String pattern = randomFrom(FormatNames.values()).getName();
+
+        IndexMetadata indexMetadata = IndexMetadata.builder("test")
+            .settings(settings(OLD_VERSION))
+            .numberOfShards(1)
+            .numberOfReplicas(0)
+            .state(indexMetdataState)
+            .putMapping(String.format(Locale.ROOT, """
+                {
+                  "properties": {
+                    "date": {
+                      "type": "date",
+                      "format": "%s"
+                    }
+                  }
+                }""", pattern))
+            .build();
+        ClusterState clusterState = ClusterState.builder(ClusterState.EMPTY_STATE)
+            .metadata(Metadata.builder().put(indexMetadata, true))
+            .blocks(clusterBlocksForIndices(indexMetadata))
+            .build();
+        DeprecationIssue expected = new DeprecationIssue(
+            DeprecationIssue.Level.CRITICAL,
+            "Old index with a compatibility version < 8.0",
+            "https://www.elastic.co/guide/en/elastic-stack/9.0/upgrading-elastic-stack.html",
+            "This index has version: " + OLD_VERSION.toReleaseVersion(),
+            false,
+            singletonMap("reindex_required", true)
+        );
+        Map<String, List<DeprecationIssue>> issuesByIndex = checker.check(
+            clusterState,
+            new DeprecationInfoAction.Request(TimeValue.THIRTY_SECONDS),
+            emptyPrecomputedData
+        );
+        List<DeprecationIssue> issues = issuesByIndex.get("test");
+        assertEquals(singletonList(expected), issues);
+    }
+
     private IndexMetadata indexMetadata(String indexName, IndexVersion indexVersion) {
         return IndexMetadata.builder(indexName)
             .settings(settings(indexVersion))