Defaulting to ENV vars during container build is problematic

[Richtermeister]

First off, this bundle has come a long way and I really like it now, great job, and thank you!

One snag I ran into though:

Expected behavior

According to the documentation I can configure this bundle via ENV vars, specifically, setting BUGSNAG_API_KEY – the idea of ENV vars being that I can change their values during deploy time to produce different runtime behavior.

Observed behavior

However, by default ENV vars only end up as a default-values to the container build step, and are consequently frozen into the container as resolved value. A change to ENV vars will not affect a change to the runtime configuration, without rebuilding the container. See: https://github.com/bugsnag/bugsnag-symfony/blob/master/DependencyInjection/Configuration.php#L26

Steps to reproduce

1. Warm the cache (build container) while providing BUGSNAG_API_KEY via ENV var.
2. Start a webserver hosting the bundle with a different ENV setting.
3. Trigger error report & observe it going to the build-time account. Alternatively, look into the cached container and find frozen resolved value.

Version

1.5.0

Additional information

By explicitly specifying the api_key via ENV var, the bundle remains configurable at runtime:

bugsnag:
    api_key: "%env(BUGSNAG_API_KEY)%"

My recommendation would be to avoid setting default values via ENV inside the Configuration class and instead require them to be specified inside the bugsnag.yml config file.

[Cawllec]

I think this is fair, if environment variables are expected to configure options that should be respected in all environments. What do you think @GrahamCampbell?