ES|QL: better validation of GROK patterns (#112200)

Catch exceptions when building GROK with a wrong pattern, and emit a
client exception with a meaningful error message.

Fixes #112111

Author: luigidellaquila

docs/changelog/112200.yaml

@@ -0,0 +1,6 @@
+pr: 112200
+summary: "ES|QL: better validation of GROK patterns"
+area: ES|QL
+type: bug
+issues:
+ - 112111

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

@@ -57,6 +57,7 @@
 import org.elasticsearch.xpack.esql.plan.logical.meta.MetaFunctions;
 import org.elasticsearch.xpack.esql.plan.logical.show.ShowInfo;
 import org.elasticsearch.xpack.esql.plugin.EsqlPlugin;
+import org.joni.exception.SyntaxException;
 
 import java.util.ArrayList;
 import java.util.Arrays;
@@ -153,7 +154,12 @@ public PlanFactory visitGrokCommand(EsqlBaseParser.GrokCommandContext ctx) {
         return p -> {
             Source source = source(ctx);
             String pattern = visitString(ctx.string()).fold().toString();
-            Grok.Parser grokParser = Grok.pattern(source, pattern);
+            Grok.Parser grokParser;
+            try {
+                grokParser = Grok.pattern(source, pattern);
+            } catch (SyntaxException e) {
+                throw new ParsingException(source, "Invalid grok pattern [{}]: [{}]", pattern, e.getMessage());
+            }
             validateGrokPattern(source, grokParser, pattern);
             Grok result = new Grok(source(ctx), p, expression(ctx.primaryExpression()), grokParser);
             return result;

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

@@ -791,6 +791,11 @@ public void testGrokPattern() {
             "line 1:22: Invalid GROK pattern [%{NUMBER:foo} %{WORD:foo}]:"
                 + " the attribute [foo] is defined multiple times with different types"
         );
+
+        expectError(
+            "row a = \"foo\" | GROK a \"(?P<justification>.+)\"",
+            "line 1:18: Invalid grok pattern [(?P<justification>.+)]: [undefined group option]"
+        );
     }
 
     public void testLikeRLike() {