ESQL: Keep DROP attributes when resolving field names

docs/changelog/127009.yaml

@@ -0,0 +1,6 @@
+pr: 127009
+summary: "ESQL: Keep `DROP` attributes when resolving field names"
+area: ES|QL
+type: bug
+issues:
+  - 126418

x-pack/plugin/esql/qa/server/src/main/java/org/elasticsearch/xpack/esql/qa/rest/generative/GenerativeRestTest.java

@@ -54,7 +54,6 @@ public abstract class GenerativeRestTest extends ESRestTestCase {
         "token recognition error at: '``", // https://github.com/elastic/elasticsearch/issues/125870
         "Unknown column \\[.*\\]", // https://github.com/elastic/elasticsearch/issues/126026
         "optimized incorrectly due to missing references", // https://github.com/elastic/elasticsearch/issues/116781
-        "No matches found for pattern", // https://github.com/elastic/elasticsearch/issues/126418
         "The incoming YAML document exceeds the limit:" // still to investigate, but it seems to be specific to the test framework
     );
 

x-pack/plugin/esql/qa/testFixtures/src/main/resources/drop.csv-spec

@@ -172,3 +172,19 @@ Milky Way
 Milky Way
 Milky Way
 ;
+
+dropAgainWithWildcardAfterEval
+required_capability: drop_again_with_wildcard_after_eval
+from languages
+| eval language_code = 12, x = 13
+| drop language_code
+| drop language*
+| keep x
+| limit 3
+;
+
+x:integer
+13
+13
+13
+;

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/action/EsqlCapabilities.java

@@ -1019,6 +1019,12 @@ public enum Cap {
          */
         FIX_JOIN_MASKING_EVAL,
 
+        /**
+         * Support for keeping `DROP` attributes when resolving field names.
+         * see <a href="https://github.com/elastic/elasticsearch/issues/126418"> ES|QL: no matches for pattern #126418 </a>
+         */
+        DROP_AGAIN_WITH_WILDCARD_AFTER_EVAL,
+
         /**
          * Support last_over_time aggregation that gets evaluated per time-series
          */

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/session/EsqlSession.java

@@ -626,7 +626,7 @@ static PreAnalysisResult fieldNames(LogicalPlan parsed, Set<String> enrichPolicy
                 p.forEachExpression(UnresolvedNamePattern.class, up -> {
                     var ua = new UnresolvedAttribute(up.source(), up.name());
                     referencesBuilder.add(ua);
-                    if (p instanceof Keep) {
+                    if (p instanceof Keep || p instanceof Drop) {
                         keepCommandRefsBuilder.add(ua);
                     }
                 });

x-pack/plugin/esql/src/test/java/org/elasticsearch/xpack/esql/session/IndexResolverFieldNamesTests.java

@@ -1710,6 +1710,16 @@ public void testEnrichAndJoinMaskingEvalWh() {
             | keep emp_no, language_name""", Set.of("emp_no", "language_name", "languages", "language_name.*", "languages.*", "emp_no.*"));
     }
 
+    public void testDropAgainWithWildcardAfterEval() {
+        assertFieldNames("""
+            from employees
+            | eval full_name = 12
+            | drop full_name
+            | drop *name
+            | keep emp_no
+            """, Set.of("emp_no", "emp_no.*", "*name", "*name.*"));
+    }
+
     private Set<String> fieldNames(String query, Set<String> enrichPolicyMatchFields) {
         var preAnalysisResult = new EsqlSession.PreAnalysisResult(null);
         return EsqlSession.fieldNames(parser.createStatement(query), enrichPolicyMatchFields, preAnalysisResult).fieldNames();