[🐛 Bug]: TypeScript types for driver.wait return single item instead of Array

[slhck]

What happened?

I am using:

• @types/selenium-webdriver: 4.1.24
• selenium-webdriver: 4.22.0
• typescript: 5.5.3

The TypeScript definition for webdriver.wait seems to be wrong or inconsistent.

In the below code snippet, I get an error:

Property 'length' does not exist on type 'WebElement'.ts(2339)

Yet, result is an array of WebElements:

> result.at(0)
WebElement {driver_: Driver, id_: Promise, log_: Logger}

Since driver.wait returns a WebElementPromise, it assumes it's only a single item, whereas the until.elementsLocated returns a Condition<WebElement[]>.

How can we reproduce the issue?

import webdriver, { By, until } from "selenium-webdriver";
import chrome from "selenium-webdriver/chrome.js";

const chromeOptions = new chrome.Options().addArguments(
  "--mute-audio",
  "--autoplay-policy=no-user-gesture-required"
);

const driver = new webdriver.Builder()
  .forBrowser("chrome")
  .setChromeOptions(chromeOptions)
  .build();

await driver.get("https://www.youtube.com");

const primaryBtnsPromise = driver.wait(
  until.elementsLocated(By.css("tp-yt-paper-button.style-primary"))
);
const rejectButtonPromise = driver.wait(
  until.elementsLocated(By.css('button[aria-label*="Reject"]'))
);

const result = await Promise.race([primaryBtnsPromise, rejectButtonPromise]);

console.log("result", Array.isArray(result)); // --> true!

if (result.length <= 0) {
  throw new Error(`No buttons found!`);
}

Relevant log output

See above

Operating System

N/A

Selenium version

4.22.0

What are the browser(s) and version(s) where you see this issue?

N/A

What are the browser driver(s) and version(s) where you see this issue?

N/A

Are you using Selenium Grid?

No

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[slhck]

If I knew which change caused that regression I could have a deeper look, but the types and inner workings are bit too complex for me to grasp as an outsider.

[marlapativ]

@slhck One workaround is to force the constraints to use WebElement[]

const primaryBtnsPromise = driver.wait<WebElement[]>(
  until.elementsLocated(By.css("tp-yt-paper-button.style-primary"))
);
const rejectButtonPromise = driver.wait<WebElement[]>(
  until.elementsLocated(By.css('button[aria-label*="Reject"]'))
);

From what I understand, the issue shows up because typescript cannot differentiate between the following for wait function

1. WebElementCondition (Condition<WebElement>)
2. Condition<WebElement[]>

[slhck]

Yes, that might work. The thing is, this seems to be a regression. I have only encountered this error after upgrading from an older version of the types/selenium.

[marlapativ]

@diemol, Can I pick this issue?

Also if I understand correctly, I'd need to do changes in the types DefinitelyTyped repo, Correct?

[harsha509]

Hi @marlapativ,

Yes, changing it there is correct.

I've looked into the types, and it seems new types have been merged recently. However, using generics is still the best approach for now. as returning Promise<WebElement | WebElement[]> from wait requires type guarding in code Array.isArray(result)

For WebElements, you should use driver.wait<WebElement[]> as it automatically infers the correct type for WebElement.

Thanks, Sri

[slhck]

Is there any indication as to which changes introduced this regression? I am a bit lost in the number of files and commits.

But yes, the return value of driver.wait should be generically inferred from the thing it's waiting for, as until.elementsLocated returns an array, always.