Add validation step to quoted join query construction

muted-tests.yml

@@ -354,9 +354,6 @@ tests:
 - class: org.elasticsearch.index.shard.StoreRecoveryTests
   method: testAddIndices
   issue: https://github.com/elastic/elasticsearch/issues/124104
-- class: org.elasticsearch.xpack.esql.parser.StatementParserTests
-  method: testInvalidJoinPatterns
-  issue: https://github.com/elastic/elasticsearch/issues/125536
 - class: org.elasticsearch.xpack.inference.registry.ModelRegistryMetadataTests
   method: testUpgrade
   issue: https://github.com/elastic/elasticsearch/issues/125554

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/parser/LogicalPlanBuilder.java

@@ -11,6 +11,7 @@
 import org.antlr.v4.runtime.Token;
 import org.antlr.v4.runtime.tree.ParseTree;
 import org.elasticsearch.Build;
+import org.elasticsearch.cluster.metadata.IndexNameExpressionResolver;
 import org.elasticsearch.common.Strings;
 import org.elasticsearch.core.Tuple;
 import org.elasticsearch.dissect.DissectException;
@@ -568,6 +569,13 @@ public PlanFactory visitJoinCommand(EsqlBaseParser.JoinCommandContext ctx) {
                 rightPattern
             );
         }
+        if (rightPattern.contains(IndexNameExpressionResolver.SelectorResolver.SELECTOR_SEPARATOR)) {
+            throw new ParsingException(
+                source(target),
+                "invalid index pattern [{}], index pattern selectors are not supported in LOOKUP JOIN",
+                rightPattern
+            );
+        }
 
         UnresolvedRelation right = new UnresolvedRelation(
             source(target),

x-pack/plugin/esql/src/test/java/org/elasticsearch/xpack/esql/parser/StatementParserTests.java

@@ -80,6 +80,7 @@
 import static org.elasticsearch.xpack.esql.EsqlTestUtils.paramAsPattern;
 import static org.elasticsearch.xpack.esql.EsqlTestUtils.referenceAttribute;
 import static org.elasticsearch.xpack.esql.IdentifierGenerator.Features.CROSS_CLUSTER;
+import static org.elasticsearch.xpack.esql.IdentifierGenerator.Features.DATE_MATH;
 import static org.elasticsearch.xpack.esql.IdentifierGenerator.Features.INDEX_SELECTOR;
 import static org.elasticsearch.xpack.esql.IdentifierGenerator.Features.WILDCARD_PATTERN;
 import static org.elasticsearch.xpack.esql.IdentifierGenerator.randomIndexPattern;
@@ -3142,18 +3143,21 @@ public void testInvalidJoinPatterns() {
         if (EsqlCapabilities.Cap.INDEX_COMPONENT_SELECTORS.isEnabled()) {
             {
                 // Selectors are not supported on the left of the join query if used with cluster ids.
-                var fromPatterns = randomIndexPatterns(CROSS_CLUSTER);
+                // Unquoted case: The language specification does not allow mixing `:` and `::` characters in an index expression
+                var fromPatterns = randomIndexPatterns(CROSS_CLUSTER, without(DATE_MATH));
                 // We do different validation based on the quotation of the pattern
                 // Autogenerated patterns will not mix cluster ids with selectors. Unquote it to ensure stable tests
                 fromPatterns = unquoteIndexPattern(fromPatterns) + "::data";
                 var joinPattern = randomIndexPattern(without(CROSS_CLUSTER), without(WILDCARD_PATTERN), without(INDEX_SELECTOR));
                 expectError(
                     "FROM " + fromPatterns + " | LOOKUP JOIN " + joinPattern + " ON " + randomIdentifier(),
-                    "mismatched input '::' expecting {<EOF>, '|', ',', 'metadata'}"
+                    "mismatched input '::' expecting {"
                 );
             }
             {
                 // Selectors are not supported on the left of the join query if used with cluster ids.
+                // Quoted case: The language specification allows mixing `:` and `::` characters in a quoted expression, but this usage
+                // must cause a validation exception in the non-generated code.
                 var fromPatterns = randomIndexPatterns(CROSS_CLUSTER, without(INDEX_SELECTOR));
                 // We do different validation based on the quotation of the pattern
                 // Autogenerated patterns will not mix cluster ids with selectors. Unquote, modify, and requote it to ensure stable tests
@@ -3166,12 +3170,31 @@ public void testInvalidJoinPatterns() {
             }
             {
                 // Selectors are not yet supported in join patterns on the right.
-                var joinPattern = randomIndexPattern(without(CROSS_CLUSTER), without(WILDCARD_PATTERN), INDEX_SELECTOR);
+                // Unquoted case: The language specification does not allow mixing `:` and `::` characters in an index expression
+                var joinPattern = randomIndexPattern(without(CROSS_CLUSTER), without(WILDCARD_PATTERN), without(DATE_MATH), INDEX_SELECTOR);
+                // We do different validation based on the quotation of the pattern, so forcefully unquote the expression instead of leaving
+                // it to chance.
+                joinPattern = unquoteIndexPattern(joinPattern);
                 expectError(
-                    "FROM " + randomIndexPatterns() + " | LOOKUP JOIN " + joinPattern + " ON " + randomIdentifier(),
+                    "FROM " + randomIndexPatterns(without(CROSS_CLUSTER)) + " | LOOKUP JOIN " + joinPattern + " ON " + randomIdentifier(),
                     "extraneous input ':' expecting {QUOTED_STRING, UNQUOTED_SOURCE}"
                 );
             }
+            {
+                // Selectors are not yet supported in join patterns on the right.
+                // Quoted case: The language specification allows `::` characters in a quoted expression, but this usage
+                // must cause a validation exception in the non-generated code.
+                var joinPattern = randomIndexPattern(without(CROSS_CLUSTER), without(WILDCARD_PATTERN), without(DATE_MATH), INDEX_SELECTOR);
+                // We do different validation based on the quotation of the pattern, so forcefully quote the expression instead of leaving
+                // it to chance.
+                joinPattern = "\"" + unquoteIndexPattern(joinPattern) + "\"";
+                expectError(
+                    "FROM " + randomIndexPatterns(without(CROSS_CLUSTER)) + " | LOOKUP JOIN " + joinPattern + " ON " + randomIdentifier(),
+                    "invalid index pattern ["
+                        + unquoteIndexPattern(joinPattern)
+                        + "], index pattern selectors are not supported in LOOKUP JOIN"
+                );
+            }
         }
     }