@mapwhit/style-expressions/lib/expression/definitions/var.js

Process expressions in map style.

export default class Var {
  constructor(name, boundExpression) {
    this.type = boundExpression.type;
    this.name = name;
    this.boundExpression = boundExpression;
  }

  static parse(args, context) {
    if (args.length !== 2 || typeof args[1] !== 'string')
      return context.error(`'var' expression requires exactly one string literal argument.`);

    const name = args[1];
    if (!context.scope.has(name)) {
      return context.error(
        `Unknown variable "${name}". Make sure "${name}" has been bound in an enclosing "let" expression before using it.`,
        1
      );
    }

    return new Var(name, context.scope.get(name));
  }

  evaluate(ctx) {
    return this.boundExpression.evaluate(ctx);
  }

  eachChild() {}

  possibleOutputs() {
    return [undefined];
  }
}