Painless: Fix Semicolon Regression (#33212)

Trailers (statements following something like an if statement) that don't use brackets currently require a semicolon even if they're the last statement. This is a regression caused by (#29566) and noted by (#33193). This change fixes the regression and adds a test for the broken case.

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

@@ -22,7 +22,7 @@ parser grammar PainlessParser;
 options { tokenVocab=PainlessLexer; }
 
 source
-    : function* statement* dstatement? EOF
+    : function* statement* EOF
     ;
 
 function
@@ -35,7 +35,7 @@ parameters
 
 statement
     : rstatement
-    | dstatement SEMICOLON
+    | dstatement ( SEMICOLON | EOF )
     ;
 
 // Note we use a predicate on the if/else case here to prevent the

modules/lang-painless/src/main/java/org/elasticsearch/painless/antlr/PainlessLexer.java

@@ -1,17 +1,13 @@
 // ANTLR GENERATED CODE: DO NOT EDIT
 package org.elasticsearch.painless.antlr;
-
-import org.antlr.v4.runtime.CharStream;
 import org.antlr.v4.runtime.Lexer;
-import org.antlr.v4.runtime.RuleContext;
-import org.antlr.v4.runtime.RuntimeMetaData;
-import org.antlr.v4.runtime.Vocabulary;
-import org.antlr.v4.runtime.VocabularyImpl;
-import org.antlr.v4.runtime.atn.ATN;
-import org.antlr.v4.runtime.atn.ATNDeserializer;
-import org.antlr.v4.runtime.atn.LexerATNSimulator;
-import org.antlr.v4.runtime.atn.PredictionContextCache;
+import org.antlr.v4.runtime.CharStream;
+import org.antlr.v4.runtime.Token;
+import org.antlr.v4.runtime.TokenStream;
+import org.antlr.v4.runtime.*;
+import org.antlr.v4.runtime.atn.*;
 import org.antlr.v4.runtime.dfa.DFA;
+import org.antlr.v4.runtime.misc.*;
 
 @SuppressWarnings({"all", "warnings", "unchecked", "unused", "cast"})
 abstract class PainlessLexer extends Lexer {

modules/lang-painless/src/main/java/org/elasticsearch/painless/antlr/Walker.java

@@ -261,10 +261,6 @@ public final class Walker extends PainlessParserBaseVisitor<ANode> {
             statements.add((AStatement)visit(statement));
         }
 
-        if (ctx.dstatement() != null) {
-            statements.add((AStatement)visit(ctx.dstatement()));
-        }
-
         return new SSource(scriptClassInfo, settings, sourceName, debugStream, (MainMethodReserved)reserved.pop(),
                            location(ctx), functions, globals, statements);
     }

modules/lang-painless/src/test/java/org/elasticsearch/painless/BasicAPITests.java

@@ -129,4 +129,8 @@ public class BasicAPITests extends ScriptTestCase {
         assertEquals(5, exec("org.elasticsearch.painless.FeatureTest ft = new org.elasticsearch.painless.FeatureTest();" +
             "ft.z = 5; return ft.z;"));
     }
+
+    public void testNoSemicolon() {
+        assertEquals(true, exec("def x = true; if (x) return x"));
+    }
 }

modules/lang-painless/src/test/java/org/elasticsearch/painless/RegexTests.java

@@ -278,6 +278,6 @@ public class RegexTests extends ScriptTestCase {
         IllegalArgumentException e = expectScriptThrows(IllegalArgumentException.class, () -> {
             exec("/asdf/b", false); // Not picky so we get a non-assertion error
         });
-        assertEquals("invalid sequence of tokens near ['b'].", e.getMessage());
+        assertEquals("unexpected token ['b'] was expecting one of [{<EOF>, ';'}].", e.getMessage());
     }
 }

modules/lang-painless/src/test/java/org/elasticsearch/painless/WhenThingsGoWrongTests.java

@@ -255,7 +255,7 @@ public class WhenThingsGoWrongTests extends ScriptTestCase {
             // We don't want PICKY here so we get the normal error message
             exec("def i = 1} return 1", emptyMap(), emptyMap(), null, false);
         });
-        assertEquals("invalid sequence of tokens near ['}'].", e.getMessage());
+        assertEquals("unexpected token ['}'] was expecting one of [{<EOF>, ';'}].", e.getMessage());
     }
 
     public void testBadBoxingCast() {