Progress bar overwrites previous lines if format is multiline.

[rquadling]

If you have a progress bar whose format is across multiple lines, previously outputted content gets overwritten.

Using Symfony/Console v2.8.7.

<?php
use Symfony\Component\Console\Helper\ProgressBar;
use Symfony\Component\Console\Output\ConsoleOutput;

require_once __DIR__ . '/vendor/autoload.php';

$output = new ConsoleOutput();
$output->writeln('Line 1');
$output->writeln('Line 2');
$output->writeln('Line 3');

$bar = new ProgressBar($output);
$bar->setFormat(
    implode(
        "\n",
        [
            'Processing Loop',
            '       Progress : [%bar%]',
            '     Lines Read : %linesRead:10s%',
        ]
    )
);

foreach(range(1, 10) as $linesRead => $line){
    $bar->setMessage(number_format(1+ $linesRead), 'linesRead');
    $bar->advance();
}

$bar->finish();

outputs

Line 1
Processing Loop
       Progress : [============================]
     Lines Read :         10

In looking at the code, \Symfony\Component\Console\Helper\ProgressBar::overwrite() wants to clear lines based upon the number of lines in the progress bar format. That is fine, except on the first run.

A hack could be to not "overwrite" on the first call.

    /**
     * Overwrites a previous message to the output.
     *
     * @param string $message The message
     */
    private function overwrite($message)
    {
        static $firstTime = true;

        if ($this->overwrite) {
            if (!$firstTime) {
                // Move the cursor to the beginning of the line
                $this->output->write("\x0D");

                // Erase the line
                $this->output->write("\x1B[2K");

                // Erase previous lines
                if ($this->formatLineCount > 0) {
                    $this->output->write(str_repeat("\x1B[1A\x1B[2K", $this->formatLineCount));
                }
            }
        } elseif ($this->step > 0) {
            $this->output->writeln('');
        }

        $firstTime = false;

        $this->output->write($message);
    }

This now makes my code display correctly.

Line 1
Line 2
Line 3
Processing Loop
       Progress : [============================]
     Lines Read :         10