No option to pass through existing env vars as well as auto-reload on env change

[martenjacobs]

framework/src/Illuminate/Foundation/Console/ServeCommand.php

Lines 135 to 139 in e7ac9b1

	if ($this->option('no-reload') || ! $hasEnvironment) {
	return [$key => $value];
	}
	return in_array($key, static::$passthroughVariables) ? [$key => $value] : [$key => false];

I'm running Laravel sail in a devcontainer. I'd like to be able to pass through most environment variables to multiple containers so that I can set up MySQL with certain credentials, and use the same env vars in Laravel to connect to the database, for instance. However, I found that serving Laravel through php artisan serve will block most environment variables from the "outside" environment. This means I'd have to duplicate all my variables to the .env file for my Laravel app, or use "--no-reload", in which case the filter is ignored. Wouldn't it be possible to have both?

[JonathanGawrych]

After hours of debugging why serve via sail didn't respect the DB docker-compose.yml environment variables I set, I came across this.
I echo the confusion expressed in 700b277#commitcomment-53272381 (a comment on where the change was introduced).

I fixed it by adding to my bootstrap/app.php:

ServeCommand::$passthroughVariables[] = 'DB_HOST';
ServeCommand::$passthroughVariables[] = 'DB_PORT';

And added warning comments in both here and docker-compose.yml to keep the list in sync.

Then I realized that it used loose comparison in_array, so we can use a hack to allow anything (well, besides empty string or '0' but you won't have .env variable keys like that):

ServeCommand::$passthroughVariables[] = true;

I don't really know the downside of this... The only thing I can think of is potential confusion on a developer's part if the change the .env expecting the serve command to reload with a value, but it doesn't change because the system ENV still overrides the .env. However, I'd argue that only some system envs be respected only in serve is much more confusing. Especially since tinker will give different values. So I guess I'll add this to all laravel projects from now. If I find another downside I'll come back and amend my comment.

[jpswade]

Any variable in your .env file can be overridden by external environment variables such as server-level or system-level environment variables.

Ref: https://github.com/laravel/docs/blob/83b872eb2e81df9bead2eef7155bbc42b78c55b8/configuration.md?plain=1#L55

Sadly, this isn't true if you're using the serve command, so you need to allow the passthroughVariables as per above:

ServeCommand::$passthroughVariables[] = true;

This allows DB_HOST, etc to be passed through from the environment to PHP and therefore Laravel.

Perhaps the docs should be updated to reflect this.