As @SVillette pointed out to me via Symfony Slack, the current profiler before this PR already displayed the "log counter":

So, the real problem might be that the log counter of LoggerProfiler doesn't work.

@SVillette also mentioned that doing the following change in LoggerDataCollector::getProcessedLogs() solve the problem for them:

$logs[] = [
  ...
  'errorCounter' => isset($rawLogData['errorCounter']) ? $rawLogData['errorCounter']->getValue() : 1,
  'errorCount' => $rawLog['errorCount'] ?? 1,  // The line I added to make it worked
  ...
];

I need help to know how to move forward with this. Thanks!

This could qualify as a bug fix IMHO.
About the count, "15" looks like it's correct to me.

Hi @nicolas-grekas, I will clarify a little about what has been done.

The issue is not about global count ("15") but the count per log ("5 times").
Symfony 5.4 added a new method LoggerDataCollector::getProcessedLogs() that introduced errorCounter when processing a single log, but the template (Collector/logger.html.twig at line 241) only display log.errorCount which is never defined.

public function getProcessedLogs()
{
...
    $logs[] = [
...
        'errorCounter' => isset($rawLogData['errorCounter']) ? $rawLogData['errorCounter']->getValue() : 1,
    ];
...
    return $this->processedLogs = $logs;
}

{% macro render_log_message(category, log_index, log) %}
...
    {% if log.errorCount is defined and log.errorCount > 1 %}
         <span class="log-num-occurrences">{{ log.errorCount }} times</span>
    {% endif %}
...
{% endmacro %}

" the current profiler before this PR already displayed the "log counter""

To reformulate what @javiereguiluz said, the template was already displaying the right information but the LoggerDataCollector does not pass the errorCount when getting the processed logs.

From what I debugged $rawLogData['errorCounter'] is not defined and so errorCounter value is always 1. I cannot affirm this is always the case.

So that's why I just modified errorCounter by errorCount in the LoggerDataCollector. In addition, $rawLogData does not contain neither errorCounter nor errorCount so I just used $rawLog['errorCount'].

$logs[] = [
    'errorCount' => $rawLog['errorCount'] ?? 1,
];

I hope my explanation are clear, I can open a PR if you consider it is a bug fix.

Finally, I want to add that a global search on errorCounter only display LoggerDataCollector::getProcessedLogs() and LoggerDataCollector::testCollectFromDeprecationsLog(). I don't see any other usages.

Closing in favor of a better fix in #45302. Thanks!