In antlr visitor pattern how to navigate from one method to another

问题

I am a newbie to Antlr I wanted to know how to navigate from one parse the enter each method and I wanted the below implementation to be done using Antlr4. I am having the below-written functions.

Below is the github link of project. https://github.com/VIKRAMAS/AntlrNestedFunctionParser/tree/master

1. FUNCTION.add(Integer a,Integer b)
2. FUNCTION.concat(String a,String b)
3. FUNCTION.mul(Integer a,Integer b)

And I am storing the functions metadata like this.

Map<String,String> map=new HashMap<>();
        map.put("FUNCTION.add","Integer:Integer,Integer");
        map.put("FUNCTION.concat","String:String,String");
        map.put("FUNCTION.mul","Integer:Integer,Integer");

Where, Integer:Integer,Integer represents Integer is the return type and input params the function will accespts are Integer,Integer.

if the input is something like this

FUNCTION.concat(Function.substring(String,Integer,Integer),String)
or
FUNCTION.concat(Function.substring("test",1,1),String)

Using the visitor implementation I wanted to check whether the input is validate or not against the functions metadata stored in map.

Below is the lexer and parser that I'm using:

Lexer MyFunctionsLexer.g4:

lexer grammar MyFunctionsLexer;

FUNCTION: 'FUNCTION';

NAME: [A-Za-z0-9]+;

DOT: '.';

COMMA: ',';

L_BRACKET: '(';

R_BRACKET: ')';

Parser MyFunctionsParser.g4:

parser grammar MyFunctionsParser;

options {
    tokenVocab=MyFunctionsLexer;
}

function : FUNCTION '.' NAME '('(function | argument (',' argument)*)')';

argument: (NAME | function);

WS : [ \t\r\n]+ -> skip;

I am using Antlr4.

Below is the implementation I'm using as per the suggested answer.

Visitor Implementation: public class FunctionValidateVisitorImpl extends MyFunctionsParserBaseVisitor {

    Map<String, String> map = new HashMap<String, String>();

    public FunctionValidateVisitorImpl()
    {
        map.put("FUNCTION.add", "Integer:Integer,Integer");
        map.put("FUNCTION.concat", "String:String,String");
        map.put("FUNCTION.mul", "Integer:Integer,Integer");
        map.put("FUNCTION.substring", "String:String,Integer,Integer");
    }

    @Override
    public String visitFunctions(@NotNull MyFunctionsParser.FunctionsContext ctx) {
        System.out.println("entered the visitFunctions::");
        for (int i = 0; i < ctx.getChildCount(); ++i)
        {
            ParseTree c = ctx.getChild(i);
            if (c.getText() == "<EOF>")
                continue;
            String top_level_result = visit(ctx.getChild(i));
            System.out.println(top_level_result);
            if (top_level_result == null)
            {
                System.out.println("Failed semantic analysis: "+ ctx.getChild(i).getText());
            }
        }
        return null;
    }

    @Override
    public String visitFunction( MyFunctionsParser.FunctionContext ctx) {
        // Get function name and expected type information.
        String name = ctx.getChild(2).getText();
        String type=map.get("FUNCTION." + name);
        if (type == null)
        {
            return null; // not declared in function table.
        }
        String result_type = type.split(":")[0];
        String args_types = type.split(":")[1];
        String[] expected_arg_type = args_types.split(",");
        int j = 4;
        ParseTree a = ctx.getChild(j);
        if (a instanceof MyFunctionsParser.FunctionContext)
        {
            String v = visit(a);
            if (v != result_type)
            {
                return null; // Handle type mismatch.
            }
        } else {
            for (int i = j; i < ctx.getChildCount(); i += 2)
            {
                ParseTree parameter = ctx.getChild(i);
                String v = visit(parameter);
                if (v != expected_arg_type[(i - j)/2])
                {
                    return null; // Handle type mismatch.
                }
            }
        }
        return result_type;
    }


    @Override
    public String visitArgument(ArgumentContext ctx){
        ParseTree c = ctx.getChild(0);
        if (c instanceof TerminalNodeImpl)
        {
            // Unclear if what this is supposed to parse:
            // Mutate "1" to "Integer"?
            // Mutate "Integer" to "String"?
            // Or what?
            return c.getText();
        }
        else
            return visit(c);
    }


}

Testcalss:

public class FunctionValidate {


    public static void main(String[] args) {
        String input = "FUNCTION.concat(FUNCTION.substring(String,Integer,Integer),String)";
        ANTLRInputStream str = new ANTLRInputStream(input);
        MyFunctionsLexer lexer = new MyFunctionsLexer(str);
        CommonTokenStream tokens = new CommonTokenStream(lexer);
        MyFunctionsParser parser = new MyFunctionsParser(tokens);
        parser.removeErrorListeners(); // remove ConsoleErrorListener 
        parser.addErrorListener(new VerboseListener()); // add ours
        FunctionsContext tree = parser.functions();
        FunctionValidateVisitorImpl visitor = new FunctionValidateVisitorImpl();
        visitor.visit(tree);
    }


}

Lexer:

lexer grammar MyFunctionsLexer;
FUNCTION: 'FUNCTION';
NAME: [A-Za-z0-9]+;
DOT: '.';
COMMA: ',';
L_BRACKET: '(';
R_BRACKET: ')';
WS : [ \t\r\n]+ -> skip;

Parser:

parser grammar MyFunctionsParser;
options { tokenVocab=MyFunctionsLexer; }
functions : function* EOF;
function : FUNCTION '.' NAME '(' (function | argument (',' argument)*) ')';
argument: (NAME | function);

Verbose Listener:

public class VerboseListener  extends BaseErrorListener  {

    @Override 
    public void syntaxError(Recognizer<?, ?> recognizer, Object offendingSymbol, int line, int charPositionInLine, String msg, RecognitionException e) { 
        List<String> stack = ((Parser)recognizer).getRuleInvocationStack();
        Collections.reverse(stack); 
        throw new FunctionInvalidException("line "+line+":"+charPositionInLine+" at "+ offendingSymbol+": "+msg);

    }
}

Output: It is not entering visitor implementation as it is not printing System.out.println("entered the visitFunctions::"); statement. I am not able to walk through the child nodes by using visit method.

回答1:

You have a version skew between your generated parser and the runtime. Further, you have a version skew in your generated .java files, as though you downloaded and ran two Antlr tool versions (4.4 and 4.7.2), once without the -visitor option, then again with it. The source for MyFunctionsParser.java is in AntlrNestedFunctionParser\FunctionValidator\target\generated-sources\antlr4\com\functionvalidate\validate. At the top of the file, it says

// Generated from MyFunctionsParser.g4 by ANTLR 4.4

The source for MyFunctionsParserVisitor.java is

// Generated from com\functionvalidate\validate\MyFunctionsParser.g4 by ANTLR 4.7.2

The runtime is 4.7.2, which you state in pom.xml in AntlrNestedFunctionParser\FunctionValidator. There's MyFunctionsLexer.tokens defined in at least two locations, which one you are picking up, who knows. I'm not familiar with the Antlr build rules associated with the pom.xml, but what was generated is a mess (which is why I wrote my own build rules and editor for Antlr for C#). Make sure you clean the target directory completely, generate clean fresh up-to-date .java files, and you are using the right Antlr runtime 4.7.2.

来源：https://stackoverflow.com/questions/58684563/in-antlr-visitor-pattern-how-to-navigate-from-one-method-to-another

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java

antlr4