Is it possible to programmatically set the state of a Jison parser in your JS code?

Question

I'm writing a script in JS that utilizes Jison (https://zaa.ch/jison/) as the parser generator; I couldn't find anything in its docs that looks like the following:

// index.js - the script using the jison parser 

let myParser = require('/path/to/parser').parser; 

// some logic here to determine what the state should be 

myParser.setState('someState');
myParser.parser('someInput'); 
myParser.popState(); 

// etc.

I have some logic that cleans up responses from a server and determines some information about that output prior to sending it to my parser. Is it possible to set my parser's state outside of the .jison file itself?

Thanks!

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Edit: adding more info below:

I noticed in the code generated by Jison, the parser function/object being exported has a lexer field. The lexer has methods pushState() and popState(). I tried calling that, but I get the following error:

Example:

let myParser = require('/path/to/parser').parser; 

myParser.lexer.pushState('someState');
myParser.parse('someInput');
myParser.lexer.popState();

Output:

node index.js
C:\path\to\my\script\TheParser.js:608
        this.conditionStack.push(condition);
                            ^

TypeError: Cannot read property 'push' of undefined

Answer 1

You can't use begin/pushState before the lexer has been initialised, which happens when its setInput method is called. I guess you could call that method yourself, although the parser will call it again regardless.