LiquidJS with only control flow

liquid-setup.ts

const { Liquid } = require('liquidjs');

const engine = new Liquid();

// 1. Define the tags you want to KEEP (Control Flow only)
// Note: You only need to list the opening tags. 'endif', 'endfor', etc. are handled automatically.
const allowedTags = [
  'if', 'else', 'elsif', 'unless', 
  'for', 'break', 'continue', 'limit', 'offset',
  'case', 'when', 
  'comment', 'raw' // 'raw' is useful to escape Liquid syntax, 'comment' is harmless
];

Object.keys(engine.tags).forEach(tagName => {
  if (!allowedTags.includes(tagName)) {
    // Overwrite with a tag that throws an error
    engine.registerTag(tagName, {
        parse: function(token) {
            // This could be configured like this in a validation step
            throw new Error(`Tag "{% ${token.name} %}" is not allowed.`);

            // This could be the behavior in render service
            return '';
        }
    });
  }
});

const template = `
  {% assign x = 10 %} {% if true %}
    This works!
  {% endif %}
  
  {% include 'secret.liquid' %} `;

// Render
engine.parseAndRender(template).then(console.log);