Antlr 4 whitespace in string been eliminated - antlr

Question

I'm using Antlr 4 to build a compiler for a made up language. I'm having problems with eliminating whitespace properly. It will get rid of whitespace between tokens but it also delete whitespace within the string token which is obviously not what I want. I've tried using modes to clear this issue up with no avail.
Lexer.g4
lexer grammar WaccLexer;
SEMICOLON: ';' ;
WS: [ \n\t\r\u000C]+ -> skip;
EOL: '\n' ;
BEGIN: 'begin' ;
END: 'end' ;
SKIP: 'skip' ;
READ: 'read' ;
FREE: 'free' ;
RETURN: 'return' ;
EXIT: 'exit' ;
IS: 'is' ;
PRINT: 'print' ;
PRINTLN: 'println' ;
IF: 'if' ;
THEN: 'then' ;
ELSE: 'else' ;
FI: 'fi' ;
WHILE: 'while' ;
DO: 'do' ;
DONE: 'done' ;
NEWPAIR: 'newpair' ;
CALL: 'call' ;
FST: 'fst' ;
SND: 'snd' ;
INT: 'int' ;
BOOL: 'bool' ;
CHAR: 'char' ;
STRING: 'string' ;
PAIR: 'pair' ;
EXCLAMATION: '!' ;
LEN: 'len' ;
ORD: 'ord' ;
TOINT: 'toInt' ;
DIGIT: '0'..'9' ;
LOWCHAR: 'a'..'z' ;
R: 'r' ;
F: 'f' ;
N: 'n' ;
T: 't' ;
B: 'b' ;
ZERO: '0' ;
MULTI: '*' ;
DIVIDE: '/' ;
MOD: '%' ;
PLUS: '+' ;
MINUS: '-' ;
GT: '>' ;
GTE: '>=' ;
LT: '<' ;
LTE: '<=' ;
DOUBLEEQUAL: '==' ;
EQUAL: '=' ;
NOTEQUAL: '!=' ;
AND: '&&' ;
OR: '||' ;
UNDERSCORE: '_' ;
UPCHAR: 'A'..'Z' ;
OPENSQUARE: '[' ;
CLOSESQUARE: ']' ;
OPENPARENTHESIS: '(' ;
CLOSEPARENTHESIS: ')' ;
TRUE: 'true' ;
FALSE: 'false' ;
SINGLEQUOT: '\'' ;
DOUBLEQUOT: '\"' ;
BACKSLASH: '\\' ;
COMMA: ',' ;
NULL: 'null' ;
OPENSTRING : DOUBLEQUOT -> pushMode(STRINGMODE) ;
COMMENT: '#' ~[\r\n]* '\r'? '\n' -> skip ;
mode STRINGMODE ;
CLOSESTRING : DOUBLEQUOT -> popMode ;
CHARACTER : ~[\"\'\\] | (BACKSLASH ESCAPEDCHAR) ;
STRLIT : (CHARACTER)* ;
ESCAPEDCHAR : ZERO
| B
| T
| N
| F
| R
| DOUBLEQUOT
| SINGLEQUOT
| BACKSLASH
;
Parser.g4
parser grammar WaccParser;
options {
tokenVocab=WaccLexer;
}
program : BEGIN (func)* stat END EOF;
func : type ident OPENPARENTHESIS (paramlist)? CLOSEPARENTHESIS IS stat END ;
paramlist : param (COMMA param)* ;
param : type ident ;
stat : SKIP
| type ident EQUAL assignrhs
| assignlhs EQUAL assignrhs
| READ assignlhs
| FREE expr
| RETURN expr
| EXIT expr
| PRINT expr
| PRINTLN expr
| IF expr THEN stat ELSE stat FI
| WHILE expr DO stat DONE
| BEGIN stat END
| stat SEMICOLON stat
;
assignlhs : ident
| expr OPENSQUARE expr CLOSESQUARE
| pairelem
;
assignrhs : expr
| arrayliter
| NEWPAIR OPENPARENTHESIS expr COMMA expr CLOSEPARENTHESIS
| pairelem
| CALL ident OPENPARENTHESIS (arglist)? CLOSEPARENTHESIS
;
arglist : expr (COMMA expr)* ;
pairelem : FST expr
| SND expr
;
type : basetype
| type OPENSQUARE CLOSESQUARE
| pairtype
;
basetype : INT
| BOOL
| CHAR
| STRING
;
pairtype : PAIR OPENPARENTHESIS pairelemtype COMMA pairelemtype CLOSEPARENTHESIS ;
pairelemtype : basetype
| type OPENSQUARE CLOSESQUARE
| PAIR
;
expr : intliter
| boolliter
| charliter
| strliter
| pairliter
| ident
| expr OPENSQUARE expr CLOSESQUARE
| unaryoper expr
| expr binaryoper expr
| OPENPARENTHESIS expr CLOSEPARENTHESIS
;
unaryoper : EXCLAMATION
| MINUS
| LEN
| ORD
| TOINT
;
binaryoper : MULTI
| DIVIDE
| MOD
| PLUS
| MINUS nus
| GT
| GTE
| LT
| LTE
| DOUBLEEQUAL
| NOTEQUAL
| AND
| OR
;
ident : (UNDERSCORE | LOWCHAR | UPCHAR) (UNDERSCORE | LOWCHAR | UPCHAR | DIGIT)* ;
intliter : (intsign)? (digit)+ ;
digit : DIGIT ;
intsign : PLUS
| MINUS
;
boolliter : TRUE
| FALSE
;
charliter : CHARACTER;
strliter : OPENSTRING STRLIT CLOSESTRING;
arrayliter : OPENSQUARE (expr (COMMA expr)*)? CLOSESQUARE ;
Please also remember that comment starting with # need to be ignored. Thanks in advance.

Answer 1

The OPENSTRING lexer rule will never be matched in your grammar because the DOUBLEQUOT rule matches exactly the same input sequence and appears before it in the grammar. If you want to define a lexer rule, but you do not actually want that lexer rule to create a token on its own, then you need to define the rule with the fragment modifier.
fragment DOUBLEQUOT : '"';
In addition, you need to correct the warnings that appear when you generate code for your grammar. At least one of them (defined as EPSILON_TOKEN) indicates a major mistake that you made that used to be an error in ANTLR 4.0 but was changed to a warning in ANTLR 4.1 since there is an edge case where it can be used without problems.