How to capture all data from part of the input with ANTLR4 visitor - Stack Overflow

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I'd like to replicate the 'here' document from the bash scripting language so I need to capture all data between a start and end point.

This is my grammar;

options {   tokenVocab = HereLexer; }

doc : part* EOF ;

part: hereDocument | ID;

hereDocument: HERE_START   DATA_BLOCK  HERE_END ;

This is the lexer (provided in previous question How to capture all data from part of the input);

@members {
  String hereStart = null;

  boolean hereEndAhead() {
    for (int i = 1; i <= hereStart.length(); i++) {
      if (hereStart.charAt(i - 1) != _input.LA(i)) {
        return false;
      }
    }
    return true;
  }
}

ID
 : [a-zA-Z_] [a-zA-Z_0-9]*
 ;

HERE_START
 : '<<' ID {hereStart = getText().substring(2);} -> pushMode(HereMode)
 ;

SPACE
 : [ \t\r\n] -> skip
 ;


mode HereMode;

HERE_END
 : {hereEndAhead()}? [a-zA-Z_] [a-zA-Z_0-9]* -> popMode
 ;

DATA_BLOCK
 : ({!hereEndAhead()}? . )+
 ;

The lexer is able to properly tokenize the input but the parser/visitor still fails to properly parse this input;

When I run this code,

                "there\n" +
                "<<here\n" +
                "    sdfsdf\n" +
                "    !@#$%^&*()_\n" +
                "    1234567890-\n" +
                "    a111\n" +
                "here\n" +
                "done";

        HereLexer lexer = new HereLexer(CharStreams.fromString(source));
        CommonTokenStream tokens = new CommonTokenStream(lexer);
        tokens.fill();

        for (Token t : tokens.getTokens()) {
            System.out.printf("%-20s '%s'\n",
                    HereLexer.VOCABULARY.getSymbolicName(t.getType()),
                    t.getText().replace("\n", "\\n"));
        }

        HereDocVisitor<?>   visitor = new HereDocBaseVisitor<>();
        HereDoc parser = new HereDoc(new CommonTokenStream(lexer));
        visitor.visit(parser.hereDocument());

I Get this result;

ID                   'there'
HERE_START           '<<here'
DATA_BLOCK           '\n    sdfsdf\n    !@#$%^&*()_\n    1234567890-\n    a111\n'
HERE_END             'here'
ID                   'done'
EOF                  '<EOF>'
line 9:4 mismatched input '<EOF>' expecting HERE_START

The ANTLR4 tool shows this tree;

I'd like to replicate the 'here' document from the bash scripting language so I need to capture all data between a start and end point.

This is my grammar;

options {   tokenVocab = HereLexer; }

doc : part* EOF ;

part: hereDocument | ID;

hereDocument: HERE_START   DATA_BLOCK  HERE_END ;

This is the lexer (provided in previous question How to capture all data from part of the input);

@members {
  String hereStart = null;

  boolean hereEndAhead() {
    for (int i = 1; i <= hereStart.length(); i++) {
      if (hereStart.charAt(i - 1) != _input.LA(i)) {
        return false;
      }
    }
    return true;
  }
}

ID
 : [a-zA-Z_] [a-zA-Z_0-9]*
 ;

HERE_START
 : '<<' ID {hereStart = getText().substring(2);} -> pushMode(HereMode)
 ;

SPACE
 : [ \t\r\n] -> skip
 ;


mode HereMode;

HERE_END
 : {hereEndAhead()}? [a-zA-Z_] [a-zA-Z_0-9]* -> popMode
 ;

DATA_BLOCK
 : ({!hereEndAhead()}? . )+
 ;

The lexer is able to properly tokenize the input but the parser/visitor still fails to properly parse this input;

When I run this code,

                "there\n" +
                "<<here\n" +
                "    sdfsdf\n" +
                "    !@#$%^&*()_\n" +
                "    1234567890-\n" +
                "    a111\n" +
                "here\n" +
                "done";

        HereLexer lexer = new HereLexer(CharStreams.fromString(source));
        CommonTokenStream tokens = new CommonTokenStream(lexer);
        tokens.fill();

        for (Token t : tokens.getTokens()) {
            System.out.printf("%-20s '%s'\n",
                    HereLexer.VOCABULARY.getSymbolicName(t.getType()),
                    t.getText().replace("\n", "\\n"));
        }

        HereDocVisitor<?>   visitor = new HereDocBaseVisitor<>();
        HereDoc parser = new HereDoc(new CommonTokenStream(lexer));
        visitor.visit(parser.hereDocument());

I Get this result;

ID                   'there'
HERE_START           '<<here'
DATA_BLOCK           '\n    sdfsdf\n    !@#$%^&*()_\n    1234567890-\n    a111\n'
HERE_END             'here'
ID                   'done'
EOF                  '<EOF>'
line 9:4 mismatched input '<EOF>' expecting HERE_START

The ANTLR4 tool shows this tree;

• antlr4

Share Improve this question Follow asked Mar 27 at 9:34 user1818726user1818726 13188 bronze badges 4

• Why are you doing new CommonTokenStream(lexer) twice? Your lexer has to be reset(), which rewinds the input back to the first char, but you don't do that. And you don't override it to reset your hereStart field. You need to learn how to use a debugger. – kaby76 Commented Mar 27 at 12:26
• I probably should have mentioned, I'm using antler 4.13.2 and tokens.reset is deprecated. When I created the parser I wanted to use a new token stream to make sure there were no were effects. Just to make sure I change the code to use tokens.reset and get the same result. – user1818726 Commented Mar 27 at 17:51
• The picture of the parse tree shows you called parser.doc() because the root of the tree is doc. The code you give says you called parser.hereDocument(). hereDocument() is the wrong entry point for the parse because the input starts with an ID "there". You call tokens.reset(), which is wrong, not only because it's deprecated, but it's on a token stream that you ignore because you create a new one: new CommonTokenStream(lexer) a second time. Call lexer.reset() after printing the tokens. Do not create a second token stream. Call the correct parser entry point parser.doc(). – kaby76 Commented Mar 27 at 19:03
• If you insist on creating a second CommonTokenStream, create a new lexer object and new character stream as well. lexer.reset() works fine. If the grammar writer writes a lexer base class, he must implement a reset() method. Otherwise, the state of the base class will not be reset. – kaby76 Commented Mar 27 at 19:12

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1 Answer 1

Sorted by: Reset to default 1

As mentioned in the comments: if you invoke hereDocument(), the input should only be a a here-document and not the entire input you provided in your question.

I don't know what ANTLR tool/plugin you're using, but many of these tools do not run embedded code, which might be the cause of the error you're getting.

When I run this Java code:

String source = "here\n" +
        "there\n" +
        "<<here\n" +
        "    sdfsdf\n" +
        "    !@#$%^&*()_\n" +
        "    1234567890-\n" +
        "    a111\n" +
        "here\n" +
        "done";

HereLexer lexer = new HereLexer(CharStreams.fromString(source));
HereDoc parser = new HereDoc(new CommonTokenStream(lexer));

System.out.println(parser.doc().toStringTree(parser));

the following output is printed (without errors):

(doc 
  (part here) 
  (part there) 
  (part 
    (hereDocument <<here \n    sdfsdf\n    !@#$%^&*()_\n    1234567890-\n    a111\n here)) 
  (part done) 
  <EOF>)

(I added the indentation afterwards)

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