How to handle variables and string literals as custom tag parameters

Hi, I have a custom tag where I want to be able to have an optional parameter and I want to be able to pass in either a string or variable name. For eg: {% hello_world "foo" %} (name is string “foo”, optional code is empty) or {% assign bar = "bar" %} {% hello_world bar "code1" %} (name is variable bar, optional code is string)

I am able to accomplish the second one using this code:

liquid.registerTag('hello_world', {
  parse: function (tagToken, remainTokens) {
    const tokenizer = new Tokenizer(tagToken.args, this.liquid.options.operatorsTrie);
    this.name = tokenizer.readIdentifier().content;
    this.code = tokenizer.readIdentifier().content;
    if (!this.name) throw new Error('reject tag requires a name parameter');
  },
  render: async function (scope, hash) {
    let name = await this.liquid.evalValue(this.name, scope);
    let code = await this.liquid.evalValue(this.code, scope);
    return `HELLO name=${name},code=${code}`;
  }
});

How would I modify the above custom tag to be able to accept the name or code parameters as either variable names or fixed strings while also making the code parameter optional?

[amit777]

Here is an example of a basic tag structure with 2 helper functions. Does this look like the correct way to you?

const { Liquid, Tokenizer, evalQuotedToken, TokenKind } = require('liquidjs');
const liquid = new Liquid({jsTruthy: true});

function _getLiquidToken (tokenizer) {
  const wordToken = tokenizer.readIdentifier();
  if (wordToken.content) return wordToken;
  const quotedToken = tokenizer.readQuoted()
  if (quotedToken) return quotedToken;
}

async function _getLiquidTokenValue(token, ctx, scope) {
  let ret;
  if(token?.kind == TokenKind.Quoted) { //1024
    logger.debug(`token is quoted`);
    ret = evalQuotedToken(token);
  }
  else if(token?.kind == TokenKind.Word) { //256
    ret = await ctx.evalValue(token?.content, scope);
  }
  return ret;
}

liquid.registerTag('hello_world', {
  parse: function (tagToken, remainTokens) {
    const tokenizer = new Tokenizer(tagToken.args, this.liquid.options.operatorsTrie);
    this.foo = _getLiquidToken(tokenizer);
    if(!this.foo) throw new Error('reject requires a foo parameter');
    this.bar = _getLiquidToken(tokenizer);
  },
  render: async function (scope, hash) {
    
    let foo = await _getLiquidTokenValue(this.foo, this.liquid, scope);
    let bar = await _getLiquidTokenValue(this.bar, this.liquid, scope);
    return `foo=${foo},bar=${bar}`;
  }
});

[harttle]

Hey @amit777 , I created a tutorial here: https://liquidjs.com/tutorials/parse-parameters.html

Glad to know the above snippet works for your case. Apart from Quoted and Word, Liquid value can also be Number(23) or PropertyAccess(foo.bar), you can make use of tokenizer.readValue() and evalToken() for this.

Hope it helps!