Address review comments

Author: ioanatia

x-pack/plugin/esql/src/main/antlr/lexer/ChangePoint.g4

@@ -13,6 +13,7 @@ CHANGE_POINT : 'change_point' -> pushMode(CHANGE_POINT_MODE);
 
 mode CHANGE_POINT_MODE;
 CHANGE_POINT_PIPE : PIPE -> type(PIPE), popMode;
+// explicit popMode of RP to allow CHANGE_POINT in FORK branches
 CHANGE_POINT_RP : RP -> type(RP), popMode, popMode;
 CHANGE_POINT_ON : ON -> type(ON);
 CHANGE_POINT_AS : AS -> type(AS);

x-pack/plugin/esql/src/main/antlr/lexer/Enrich.g4

@@ -14,6 +14,7 @@ ENRICH : 'enrich'             -> pushMode(ENRICH_MODE);
 
 mode ENRICH_MODE;
 ENRICH_PIPE : PIPE -> type(PIPE), popMode;
+// explicit popMode of RP to allow ENRICH in FORK branches
 ENRICH_RP : RP -> type(RP), popMode, popMode;
 ENRICH_OPENING_BRACKET : OPENING_BRACKET -> type(OPENING_BRACKET), pushMode(SETTING_MODE);
 
@@ -84,7 +85,6 @@ ENRICH_FIELD_WS
 
 mode SETTING_MODE;
 SETTING_CLOSING_BRACKET : CLOSING_BRACKET -> type(CLOSING_BRACKET), popMode;
-SETTING_RP : RP -> type(RP), popMode, popMode, popMode;
 
 SETTING_COLON : COLON -> type(COLON);
 

x-pack/plugin/esql/src/main/antlr/lexer/Fork.g4

@@ -12,7 +12,9 @@ lexer grammar Fork;
 DEV_FORK :        {this.isDevVersion()}? 'fork'          -> pushMode(FORK_MODE);
 
 mode FORK_MODE;
+// commands needs to break out of their mode and the default mode when they encounter RP
 FORK_LP : LP -> type(LP), pushMode(DEFAULT_MODE);
+// explicit popMode of RP to allow FORK in FORK branches
 FORK_RP : RP -> type(RP), popMode, popMode;
 FORK_PIPE : PIPE -> type(PIPE), popMode;
 

x-pack/plugin/esql/src/main/antlr/lexer/Lookup.g4

@@ -13,6 +13,7 @@ DEV_LOOKUP :      {this.isDevVersion()}? 'lookup_🐔'      -> pushMode(LOOKUP_M
 
 mode LOOKUP_MODE;
 LOOKUP_PIPE : PIPE -> type(PIPE), popMode;
+// explicit popMode of RP to allow lookup_🐔 in FORK branches
 LOOKUP_RP : RP -> type(RP), popMode, popMode;
 LOOKUP_COLON : COLON -> type(COLON);
 LOOKUP_COMMA : COMMA -> type(COMMA);

x-pack/plugin/esql/src/main/antlr/lexer/MvExpand.g4

@@ -14,6 +14,7 @@ MV_EXPAND : 'mv_expand'       -> pushMode(MVEXPAND_MODE);
 
 mode MVEXPAND_MODE;
 MVEXPAND_PIPE : PIPE -> type(PIPE), popMode;
+// explicit popMode of RP to allow MV_EXPAND in FORK branches
 MVEXPAND_RP : RP -> type(RP), popMode, popMode;
 MVEXPAND_DOT: DOT -> type(DOT);
 MVEXPAND_PARAM : PARAM -> type(PARAM);

x-pack/plugin/esql/src/main/antlr/lexer/Project.g4

@@ -15,6 +15,7 @@ DEV_INSIST :      {this.isDevVersion()}? 'insist_🐔'      -> pushMode(PROJECT_
 
 mode PROJECT_MODE;
 PROJECT_PIPE : PIPE -> type(PIPE), popMode;
+// explicit popMode of RP to allow DROP and KEEP in FORK branches
 PROJECT_RP : RP -> type(RP), popMode, popMode;
 PROJECT_DOT: DOT -> type(DOT);
 PROJECT_COMMA : COMMA -> type(COMMA);

x-pack/plugin/esql/src/main/antlr/lexer/Rename.g4

@@ -14,6 +14,7 @@ RENAME : 'rename'             -> pushMode(RENAME_MODE);
 
 mode RENAME_MODE;
 RENAME_PIPE : PIPE -> type(PIPE), popMode;
+// explicit popMode of RP to allow RENAME in FORK branches
 RENAME_RP : RP -> type(RP), popMode, popMode;
 RENAME_ASSIGN : ASSIGN -> type(ASSIGN);
 RENAME_COMMA : COMMA -> type(COMMA);

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

@@ -3336,6 +3336,8 @@ public void testInvalidFork() {
 
         expectError("FROM foo* | FORK ( x+1 ) ( WHERE y>2 )", "line 1:20: mismatched input 'x+1'");
         expectError("FROM foo* | FORK ( LIMIT 10 ) ( y+2 )", "line 1:33: mismatched input 'y+2'");
+        expectError("FROM foo* | FORK (where true) ()", "line 1:32: mismatched input ')'");
+        expectError("FROM foo* | FORK () (where true)", "line 1:19: mismatched input ')'");
     }
 
     public void testFieldNamesAsCommands() throws Exception {