Internal error: attempt to prepend statements in disallowed (non-array) context

[ghost]

I know this is a very very old bug, and supposed to be fixed in Istanbul 0.2.9. But it still exist, and isn't fixed. If you are running a combo of Rollup+Buble+Rollup-plugin-istanbul it will happend to you. Even if I replace Buble with Babel it will still happen inside the Karma test runner.

IF I comment out Istanbul, everything works just fine.

Ref: https://github.com/gotwarlost/istanbul/issues/202

[gotwarlost]

That statement is a generic catch-all for unexpected things seen in the AST. The bug was fixed for the specific case that was reproduced there.

Unless you can provide a minimal reproducible test case, I have no idea how to debug this. Is there any way you could provide a simple test case that fails?

[kalitine]

I had the same issue. For example for this it works fine:

// src/111.js
class A {
  helloWorld () {
    console.log('Hello world!')
  }
}

export {A}

// test/111.test.js
import {A} from '../src/111.js'

it('Test', () => {
  new A().helloWorld()
})

But if I add export const STATE = 'open' to 111.js

export const STATE = 'open'

class A {
  helloWorld () {
    console.log('Hello world!')
  }
}

export {A}

It throws this exception. And if I export the STATE constant like this

const STATE = 'open'

class A {
  helloWorld () {
    console.log('Hello world!')
  }
}

export {STATE, A}

it works fine again.

[ghost]

@gotwarlost This issue can be solved if you accept the PR that have been pending for months - https://github.com/gotwarlost/istanbul/pull/507. It's related to this issue.

[ShadSterling]

It would be helpful if the error message said where in the code it sees something unexpected. Then at least I could share the particular bit of code that triggered it.

[ShadSterling]

I looks like I can avoid the error by downgrading to mocha 3.5. Any newer version seems to be incompatible with istanbul 0.4.5.