Callback/EOI never returns

[cawoodm]

I have a similar problem to #94 where invoke() does not return. The problem is intermittant. In my application I have 4 instances of a Vue component which each instantiate their own Shell and call Get-Service. As you can see below, 3 of the 4 processes return whilst the 4th (PID 15456) does not. Repeat and only 2 return. About one in 10 times all 4 return.

Here's the code: https://github.com/cawoodm/powershell-servicemanager

Could it be that the EOI detection is shaky? How does it work exactly?

[cawoodm]

I think I see the problem - you create a random string called EOI which looks like this EOI_llKGpOg8x and then you write it out using powershell after all other commands [Console]::Out.Write("${EOI}").

The problem is that this line is not always streamed on it's own but sometimes together with the user's commands so _write get's something like this:

[{"Name":"Fax","Status":1,"DisplayName":"Fax","StartType":3,"CanStop":false},{"Name":"SysMain","Status":4,"DisplayName":"SysMain","StartType":2,"CanStop":true},{"Name":"WSearch","Status":4,"DisplayName":"Windows Search","StartType":2,"CanStop":true}]
EOI_llKGpOg8x

But it expects this separately like this:

[{"Name":"Fax","Status":1,"DisplayName":"Fax","StartType":3,"CanStop":false},{"Name":"SysMain","Status":4,"DisplayName":"SysMain","StartType":2,"CanStop":true},{"Name":"WSearch","Status":4,"DisplayName":"Windows Search","StartType":2,"CanStop":true}]

EOI_llKGpOg8x

Whether the output is streamed together or not is up to child_process and out side our control.

So this line in utils.js fails:

if(chunk.compare(this.EOI) === 0) {
   cb();
   return this.emit('EOI');
}

It's doing a direct, absolute compare where it should be looking for the EOI string on a single line.

[cawoodm]

OK, I think we have a fix:

_write(chunk, encoding, cb) {
// HERE
    if(chunk.indexOf(this.EOI) >= 0) {
      this.chunksArray.push(chunk);
      cb();
      return this.emit('EOI');
    }
    this.chunksArray.push(chunk);
    return cb();
  }
  isEmpty() {
    return this.chunksArray.length === 0;
  }
  getContents() {
    return Buffer.concat(this.chunksArray);
  }
  getContentsAsString(encoding = 'utf8') {
// AND HERE
    return Buffer.concat(this.chunksArray).toString(encoding).replace(/\0/g, '').replace(this.EOI,'');
  }

[codaamok]

@cawoodm I'm not sure if that is a fix, e.g. something trivial like printing $host (in PowerShell) results in same issue with the never returning. Also, with your changes in cawoodm@863ef27 a lot of the output is truncated (still using $host as an example).

[cawoodm]

It works for my application, feel free to improve on it.

[rannn505]

Fix invoke() promise never resolves bug