Option to toggle/revert to 0.14 behaviour of Fallible SystemParams

[TheBiochemic]

What problem does this solve or what need does it fill?

In bigger Projects there is already a lot going on in the Terminal during runtime. If now forgetting to add some Resource etc. generates only logging (or nothing at all), that something won't happen, but the app otherwise launching and working often entails debugging that wouldn't be necessary in the first place, if it would just crash the program with the log message as the panic message, as it was historically.

If a Resource etc. is missing, it's supposed to interrupt my workflow, which is why i consider the old behavior a safeguard.

What solution would you like?

Some Sort of functionality to toggle the behavior globally. It could be one of these things:

• A Flag to set it to panic, log or none globally by default, with the option to override it, as seen in 0.15 (could be nice, since it could be disabled for release builds. This could be problematic with other parts of bevy potentially).
• An Option in DefaultPlugins (That defines the default behavior for all Systems. Same Problem as first Option)
• An Option to set the Default behavior on a Plugin level (All systems added via this plugin have the following behavior of none, logging once, loggin always, panic)
• Catching nonworking SystemParams (like a missing Resource) in a System without defined behaviour (not using .never_param_warn(), ...) during compile time and throwing a hard error (i'm not sure how possible that would be, if at all)

The Last option would be personally my favourite.

What alternative(s) have you considered?

Not upgrading to 0.15 just yet, until some interface is available to toggle to this or a similarly obvious behavior.

Additional context

i'm talking specifically about the feature mentioned in https://bevyengine.org/news/bevy-0-15/#fallible-system-parameters

[mockersf]

I think panics by default should be re-introduced

catching it at compile time is impossible as some of the system parameters can be made valid/invalid at runtime

[TheBiochemic]

catching at compile time not being possible makes sense, i think it was a suggestion from the bevy discord.

Restoring the previous behaviour would be great yeah. I would say the panicking along side the additional behaviour of logging/none is probably a good compromise.

I guess one of the chores might be to go through the codebase and make sure, that the Systems, that shouldn't panic on missing/unloaded SystemParams need to have the .never_param_warn(), etc.

I don't really know, what implications a Plugin wide behavior override mechanic would have, but it might help with that above chore.

[seivan]

If it's not possible to catch at compile time, then it needs to be possible to catch at boot.
Whatever it is that causes error logs to get dumped need to happen as soon as possible.

I wonder if #16638 fixes this.

[wilk10]

+1 from my side to reintroduce panics by default. It was actually good UX and very easy to fix. The warning is very easy to miss.