Promise rejected with: 'cov_2itgu9hdrb is not defined

[farhan2106]

I got the following bugs.

Promise rejected with: 'cov_2itgu9hdrb is not defined'

I am using Nightmare.js for browser automation. After investigation, the above error is thrown when I use Nightmare.evaluate api. When I remove any references to Nightmare.evaluate it is able to do coverage properly.

Am not sure it is an error with nyc or nightmare.

Forensic Information

v6.9.1 3.10.8 /Users/farhanghazali └── (empty)

[bcoe]

@farhan2106 could you share a minimal reproduction of this bug with nightmare.js? I think you've probably found a legitimate edge-case with the instrumenter, which is returning a line counting variable rather than a promise.

[farhan2106]

@bcoe I have created a sample project to replicate the error.

github project

Again, if we comment out the Nightmare.evaluate api, it will be able to generate the report properly.

The sample code is from Nightmare js github itself.

[JaKXz]

@farhan2106 I have some capacity this weekend, I will try to get back to you on this soon! Thanks for your patience.

[farhan2106]

@JaKXz Thanks for the help :)

[JaKXz]

@farhan2106 so I'm able to reproduce the issue, which is good.

I tried disabling nyc's instrumentation and going with babel-plugin-istanbul but they both produce the same error. Now I have to dive into the stack trace - but you can follow my progress here: JaKXz/temporary-nyc-error@master...fix/cov-error

[duytran]

@JaKXz I have same issue with @farhan2106, Is issue fixed? thank you.

[JaKXz]

Thanks for the ping @duytran, I'm unfortunately not available to look deeper. FWIW my fork is still alive: https://github.com/JaKXz/temporary-nyc-error/tree/fix/cov-error and you should be able to reproduce the error there. If you're able, feel free to dig into the issue and for many bonus points try to add a failing test :) though that is a lot of bonus points, because the issue might be in the istanbuljs repo

[duytran]

@JaKXz thank for reply :)! I will try look around. Thank you.

[bcoe]

@duytran @farhan2106 doing some issue cleanup; sorry that I haven't gotten to this bug yet -- will try to get a test around it as soon as possible.

[duytran]

Thank @bcoe!

[keithkml]

Nightmarejs converts functions passed to evaluate into strings, then evals them within the Electron/Chrome context. This means when the function is actually executed, Istanbul's coverage info variables are not present in scope.

The solution is to use Istanbul's coverage comment syntax:

browser
  .goto('http://...')
  .evaluate(
    /* istanbul ignore next */ 
    () => document.getElement('my-div').innerText
  )
  ...

[JaKXz]

@keithkml great find. Thank you for your explanation. It would definitely be worth documenting this in a gotchas section or something. Making this comment to myself to get on it, or, for anyone who wants an easy contribution :)

[epyx25]

Without the fix I was getting

[Error: Evaluation failed: ReferenceError: cov_1khzuukk7w is not defined
at evaluate (:1:30)]

The line /* istanbul ignore next */ solves the problem

  const evaluateRes = await page.evaluate(
     /* istanbul ignore next */
     (selector) => {return selector}, this.selector
   )

I am trying to make a base scraper class, where the inherited scraper classes have different evaluate method.
@keithkml or someone could you explain who could I make this work too?

class ScraperBase{
  evaluate(selector) {
   return selector
  }

  run() {
    const browser = await puppeteer.launch()
    const page = await browser.newPage();
    // ...
   const evaluateRes = await page.evaluate(
      /* istanbul ignore next */
      this.evaluate, this.selector
    )  
  }
}

Now I am getting

[Error: Evaluation failed: ReferenceError: cov_1khzuukk7w is not defined

again

[coreyfarrell]

@epyx25 in the example you posted you need:

class ScraperBase{
  /* istanbul ignore next */
  evaluate(selector) {
   return selector
  }

// ...
}

It's important that you prevent instrumentation of the body of the function that will be sent to the browser, so the /* istanbul ignore next */ goes before the function declaration.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.