Deno: a script that works fine in v1.4.6 doesn't work in v1.5.0

[magurotuna]

Describe the bug

I have a script that uses date-fns. This script worked fine in Deno v1.4.6, but after I upgraded to v1.5.0, it doesn't work.

how to reproduce

Create a file main.ts with the following content:

import { formatISO } from "https://deno.land/x/[email protected]/index.js";

const d = new Date();
console.log(formatISO(d));

Then run it by deno run main.ts. The output I've got is:

In v1.5.0

Check file:///tmp/deno-bug/main.ts
error: TS2555 [ERROR]: Expected at least 2 arguments, but got 1.
console.log(formatISO(d));
            ~~~~~~~~~~~~
    at file:///tmp/deno-bug/main.ts:4:13

    An argument for 'dirtyOptions' was not provided.
    export default function formatISO(dirtyDate, dirtyOptions) {
                                                 ~~~~~~~~~~~~
        at https://deno.land/x/[email protected]/formatISO/index.js:43:46

In v1.4.6:

Check file:///tmp/deno-bug/main.ts
2020-10-31T11:43:48+09:00

[lucacasonato]

cc @kitsonk

For some reason we are type checking JS.

[jsejcksn]

@magurotuna As a workaround until this is fixed, you can use a compiler hint (first line):

// @deno-types="https://unpkg.com/[email protected]/typings.d.ts"
import { formatISO } from "https://deno.land/x/[email protected]/index.js";

const d = new Date();
console.log(formatISO(d));

This will also improve your developer experience if you are using something like VS Code + the deno extension.

Aside: Not sure why the typings are excluded from that repo in deno.land/x. They are in the GitHub repo and being published to npm.

[kitsonk]

For some reason we are type checking JS.

We aren't type checking JS. The JavaScript though is influencing the types in TypeScript. I believe that the current behaviour is actually the desired behaviour. The example code provides JSDoc:

/**
 * @name formatISO
 * @category Common Helpers
 * @summary Format the date according to the ISO 8601 standard (http://support.sas.com/documentation/cdl/en/lrdict/64316/HTML/default/viewer.htm#a003169814.htm).
 *
 * @description
 * Return the formatted date string in ISO 8601 format. Options may be passed to control the parts and notations of the date.
 *
 * @param {Date|Number} date - the original date
 * @param {Object} [options] - an object with options.
 * @param {'extended'|'basic'} [options.format='extended'] - if 'basic', hide delimiters between date and time values.
 * @param {'complete'|'date'|'time'} [options.representation='complete'] - format date, time with time zone, or both.
 * @returns {String} the formatted date string
 * @throws {TypeError} 1 argument required
 * @throws {RangeError} `date` must not be Invalid Date
 * @throws {RangeError} `options.format` must be 'extended' or 'basic'
 * @throws {RangeError} `options.represenation` must be 'date', 'time' or 'complete'
 *
 * @example
 * // Represent 18 September 2019 in ISO 8601 format (UTC):
 * const result = formatISO(new Date(2019, 8, 18, 19, 0, 52))
 * //=> '2019-09-18T19:00:52Z'
 *
 * @example
 * // Represent 18 September 2019 in ISO 8601, short format (UTC):
 * const result = formatISO(new Date(2019, 8, 18, 19, 0, 52), { format: 'basic' })
 * //=> '20190918T190052'
 *
 * @example
 * // Represent 18 September 2019 in ISO 8601 format, date only:
 * const result = formatISO(new Date(2019, 8, 18, 19, 0, 52), { representation: 'date' })
 * //=> '2019-09-18'
 *
 * @example
 * // Represent 18 September 2019 in ISO 8601 format, time only (UTC):
 * const result = formatISO(new Date(2019, 8, 18, 19, 0, 52), { representation: 'time' })
 * //=> '19:00:52Z'
 */
export default function formatISO(dirtyDate, dirtyOptions) {
  if (arguments.length < 1) {
    throw new TypeError(
      `1 argument required, but only ${arguments.length} present`
    )
  }

Because it uses a syntax that isn't actually compliant with JSDoc, TypeScript doesn't understand the second argument is actually optional.

If you configure something similar under tsc like the following:

main.ts

import formatIso from "./api";

formatIso("test");

api.js

/**
 * 
 * @param {Date|Number} date - the original date
 * @param {Object} [options] - an object with options.
 */
export default function formatIso(dirtyDate, dirtyOptions) {
  console.log(dirtyDate, dirtyOptions);
}

And configure allowJs and strict in a tsconfig.json, you will get the following emitted:

main.ts:3:1 - error TS2554: Expected 2 arguments, but got 1.

3 formatIso("test");
  ~~~~~~~~~~~~~~~~~

  api.js:6:46
    6 export default function formatIso(dirtyDate, dirtyOptions) {
                                                   ~~~~~~~~~~~~
    An argument for 'dirtyOptions' was not provided.


Found 1 error.

So it was broken before and we didn't realise it. @jsejcksn "workaround" is the proper fix, but actually datefns in deno.land/x/ should actually point to a CDN that provides X-TypeScript-Types like SkyPack.

[magurotuna]

@jsejcksn
thanks for the workaround! That way I have made it work in v1.5.0. 👍

[kitsonk]

Since it is working as designed, I will close this.