Function generateParamSchema

src/core/friendly_errors/param_validator.js:225–243

    // Generate a schema for a single parameter. In the case where a parameter can
    // be of multiple types, `generateTypeSchema` is called for each type.
    const generateParamSchema = param => {
      const isOptional = param?.endsWith('?');
      param = param?.replace(/\?$/, '');

      const isRest = param?.startsWith('...') && param?.endsWith('[]');
      param = param?.replace(/^\.\.\.(.+)\[\]$/, '$1');

      let schema = generateTypeSchema(param);
      // Fallback to z.custom() because function types are no longer
      // returns a Zod schema.
      if (schema.def.type === 'function') {
        schema = z.custom(val => val instanceof Function);
      }

      if (isOptional) {
        schema = schema.optional();
      }
      return { schema, rest: isRest };
    };

    // Note that in Zod, `optional()` only checks for undefined, not the absence
    // of value.