M2.1.2 : Impossible to create an `after` interceptor when files are being downloaded by controllers

[kanduvisla]

Preconditions

Magento - develop branch
Take the \Magento\Sales\Controller\Adminhtml\Shipment\PrintAction controller for example. This has an execute()-method which triggers a downloading to the browser.

Now if you want to do something after this event with a plugin, you're out of luck. Since this controller uses \Magento\Framework\App\Response\Http\FileFactory::create() to print the PDF.

And if you look closer in this code, you'll notice the following:

if ($content !== null) {
    $this->_response->sendHeaders();
    if ($isFile) {
        $stream = $dir->openFile($file, 'r');
        while (!$stream->eof()) {
            echo $stream->read(1024);
        }
    } else {
        $dir->writeFile($fileName, $content);
        $stream = $dir->openFile($fileName, 'r');
        while (!$stream->eof()) {
            echo $stream->read(1024);
        }
    }
    $stream->close();
    flush();
    if (!empty($content['rm'])) {
        $dir->delete($file);
    }
    $this->callExit();
}

This piece if code (especially the $this->callExit()) makes it impossible to use a plugin with after (or around partially), since it hard sends an exit code. That's right: $this->callExit() is equivalent for exit(0).

I suggest that this get handles differently because exiting the code in the middle of the Magento lifecycle doesn't seems right to me. Especially if it breaks functionality like this.

Steps to reproduce

Create a plugin that executes code after \Magento\Sales\Controller\Adminhtml\Shipment\AbstractShipment\PrintAction::execute(). For example:

<type name="Magento\Sales\Controller\Adminhtml\Shipment\PrintAction">
    <plugin name="after_print_shipment"
            type="VendorModule\Plugin\Magento\Sales\Controller\Adminhtml\Shipment\PrintAction"/>
</type>

code:

function afterExecute(\Magento\Sales\Controller\Adminhtml\Shipment\PrintAction $subject, $result) {
    echo 'x';
    die;
}

Expected result

See the 'x' in the browser

Actual result

It just starts downloading; Magento ignores the plugin.

[KrystynaKabannyk]

Hello @kanduvisla, thank you for your submission. We recently made some changes to the way we process GitHub submissions to more quickly identify and respond to core code issues. Your issue is seems Feature Request or Improvement, and they should now be submitted to the new Magento 2 Feature Requests and Improvements forum (see details here).

[kanduvisla]

I don't see this as a feature request, but rather as a bug. The current way of handling downloads by controllers by directly invoking an exit()-method breaks the lifecycle of Magento. In my opinion it's the same as having a block template echo-ing it's HTML and than immediately performing a die() or exit().

[miguelbalparda]

There is a proposed fix for this #11029. Can you try it and report back?