Function scoreSchema

src/core/friendly_errors/param_validator.js:318–363

    // Helper function that scores how close the input arguments are to a schema.
    // Lower score means closer match.
    const scoreSchema = schema => {
      let score = Infinity;
      if (!(schema instanceof z.ZodTuple)) {
        console.warn('Schema below is not a tuple: ');
        printZodSchema(schema);
        return score;
      }

      const numArgs = args.length;
      const schemaItems = schema.def.items;
      const numSchemaItems = schemaItems.length;
      const numRequiredSchemaItems = schemaItems
        .filter(item => !item.isOptional())
        .length;

      if (numArgs >= numRequiredSchemaItems && numArgs <= numSchemaItems) {
        score = 0;
      }
      // Here, give more weight to mismatch in number of arguments.
      //
      // For example, color() can either take [Number, Number?] or
      // [Number, Number, Number, Number?] as list of parameters.
      // If the user passed in 3 arguments, [10, undefined, undefined], it's
      // more than likely that they intended to pass in 3 arguments, but the
      // last two arguments are invalid.
      //
      // If there's no bias towards matching the number of arguments, the error
      // message will show that we're expecting at most 2 arguments, but more
      // are received.
      else {
        score = Math.abs(
          numArgs < numRequiredSchemaItems ?
            numRequiredSchemaItems - numArgs :
            numArgs - numSchemaItems
        ) * 4;
      }

      for (let i = 0; i < Math.min(schemaItems.length, args.length); i++) {
        const paramSchema = schemaItems[i];
        const arg = args[i];

        if (!paramSchema.safeParse(arg).success) score++;
      }

      return score;
    };

    // Default to the first schema, so that we are guaranteed to return a result.
    let closestSchema = schema.def.options[0];