hotfix: replace non-working condition that blocks flush from clearing the logs

[Sailboat265]

Q	A
Bug fix?	yes
New feature?	no
BC breaks?	no
Deprecations?	no
Tests pass?	yes
Fixed tickets	#4553
License	MIT
Doc PR	N/A

Changes explanation

Although the pm2 docs mentioned users can pass <app_id> as an argument to pm2 flush <...>, the code doesn't recognize that. So we will be using this instead:

else if (l.pm2_env.pm_id == api || l.pm2_env.name === api) {
    <...>
}

Next, in the flush function, the condition to flush a file is depended as below:

if (l.pm2_env.pm_out_log_path.lastIndexOf('/') < l.pm2_env.pm_out_log_path.lastIndexOf(api))

The condition is fine, however, when the name of an app has space, the flush command will never succeed.

Here's why:

Let's say an app's name is My Cool Server, the log file will be created as <...home_dir...>/.pm2/logs/My-Cool-Server-out.log.

Take note that any spaces in the app name have been replaced with hyphens (-).

So when a user tries to do pm2 flush "My Cool Server". The condition will be comparing the last occurrence of / and api.
Since api is the argument passed from the user, so the value will be My Cool Server.

Now, the value of l.pm2_env.pm_out_log_path will be /home/user/.pm2/logs/My-Cool-Server-out.log. The lastIndexOf func will try to find My Cool Server from the log path name. But it will never work because there are hyphens (-) in the filename! Hence, the if-else condition is never passed, which is why the flush command doesn't flush the logs!

Hence, it's now replaced with the code below:

if (l.pm2_env.pm_out_log_path && fs.existsSync(FILEPATH))

Here, we will check whether the string l.pm2_env.pm_out_log_path has any value, then we will use fs.existsSync() to check whether the file exists or not. If both returned true, we will then proceed to flush the logs.

---

Note: The issues are present in both, the development and stable version of pm2.

A screenshot of the issue:

After applying the fix:

Now, it works fine with app_name that has spaces too!