Single line comments can end in newline or EOF. Fixes #11815 (#11816)

* Single line comments can end in newline or EOF. Fixes #11815

Signed-off-by: camerondurham <u64.cam@gmail.com>

* Re-add license to autogen parser files

Signed-off-by: camerondurham <u64.cam@gmail.com>

* Remove noise from changelog

Signed-off-by: Cameron Durham <u64.cam@gmail.com>

* Accept single-line comments until newline char

Signed-off-by: Cameron Durham <u64.cam@gmail.com>

---------

Signed-off-by: camerondurham <u64.cam@gmail.com>
Signed-off-by: Cameron Durham <u64.cam@gmail.com>

CHANGELOG.md

@@ -218,6 +218,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 - Fix Automatic addition of protocol broken in #11512 ([#11609](https://github.com/opensearch-project/OpenSearch/pull/11609))
 - Fix issue when calling Delete PIT endpoint and no PITs exist ([#11711](https://github.com/opensearch-project/OpenSearch/pull/11711))
 - Fix tracing context propagation for local transport instrumentation ([#11490](https://github.com/opensearch-project/OpenSearch/pull/11490))
+- Fix parsing of single line comments in `lang-painless` ([#11815](https://github.com/opensearch-project/OpenSearch/issues/11815))
 
 ### Security
 

modules/lang-painless/src/main/antlr/PainlessLexer.g4

@@ -25,7 +25,7 @@ protected abstract boolean isSlashRegex();
 }
 
 WS: [ \t\n\r]+ -> skip;
-COMMENT: ( '//' .*? [\n\r] | '/*' .*? '*/' ) -> skip;
+COMMENT: ( '//' ~[\n\r]* | '/*' .*? '*/' ) -> skip;
 
 LBRACK:    '{';
 RBRACK:    '}';