Nightwatch: an awaited waitForElementPresent returns before the wait runs when the plugin is loaded #457

What happens

With @wdio/nightwatch-devtools loaded, an awaited waitForElementPresent returns before the wait has run, so the commands after it run first:

await browser.click('button[type="submit"]')        // navigates to /secure
await browser.waitForElementPresent('#flash', 2000)  // returns at once
const text = await browser.getText('#flash')         // runs before the wait
await browser.click('#logout')                       // navigates back to /login
// only now does the wait poll for #flash, on /login, and time out

The test then fails on a timeout it would not have hit. The same spec against the same pages with the plugin removed passes, with the element present after about 500 ms. Seen in 9 of 9 runs while extending the conformance scenarios (#455).

Why it matters

The plugin changes the outcome of the user's own test, which is the one thing an observer must never do.

Expected

await browser.waitForElementPresent(...) resolves only after the wait has finished, with or without the plugin, so the following commands run against the page the wait saw.

Where to look

The plugin wraps Nightwatch commands to capture them (packages/nightwatch-devtools/src/helpers/browserProxy.ts). The wrapper likely resolves the awaited chainable before Nightwatch's queued wait has executed, so the user's await no longer waits for it.