Simplify _prefixes

[apotonick]

Summary

This simplifies the logic to compile the _prefixes array used for view inheritance. The change allows overriding ::_local_prefixes which didn't work before.

Implementation

It is now implemented with a proper recursion travelling up the inheritance chain instead of doing all the work locally in the concrete controller. Controllers in the chain can now define their local _prefixes by overriding _local_prefixes (we can rename that). This didn't work before.

We use this extensively in Cells for the new Trailblazer file layout. I thought it might be helpful to push that back to the core.

[josevalim]

If the goal is to make _local_prefixes overridable, it needs to be properly documented, tested and probably lose the underscore. Also, I would rather have such in the instance (maybe as prefixes) rather than in the class.

[apotonick]

Totally agree about the proper documentation and testing and I will add that once you give me the OK 😁

Overriding on the instance level is still possible by overriding #_prefixes. As this is pretty uncommon, overriding ::_local_prefixes would make sense for most parties.

I don't know what's the deal with those underscored methods, we can remove them, I don't see what they stand for.

Thanks for your prompt relpy, @josevalim!

[josevalim]

Underscored methods are private. They are not supposed to be removed if they are meant to be private.

[apotonick]

The problem is that those methods should be public but might interfere with actual controller actions. If ::_local_prefixes remained "private" what would be the problem with other controllers overriding it? Would that be an interface violation or how do you mean "not supposed to be removed"?

I personally find it OK to leave them underscored, just to avoid the hassle with name clashes.

Other than that my only concern is that I ruthlessly removed parent_prefixes without deprecating it. That should be alright?!

[apotonick]

Here's what I wanna do.

1. Rename ::_local_prefixes to ::local_prefixes to signalise it is meant to be overridden.
2. Document the latter.
3. Test the latter.
4. Document removal of parent_prefixes.

[rafaelfranca]

@apotonick seems a good plan.

Also I think if parent_prefix still can be implemented is better to deprecate first.

[apotonick]

@rafaelfranca Do you have an example where a method is marked as deprecated if it is defined (in Rails)? I will then inform the user about the deprecation of ::parent_prefixes as I am a nice person.

[rafaelfranca]

hmmm. I don't think we have this. I thought we want to deprecate the usage not the definition. So I guess the only way if checking when calling _prefixes on the instance. If there is a parent_prefixes defined we show the warning.

[apotonick]

Yeah, that's what I meant as well - I just thought there's an automation in Rails for that 😉

[rafaelfranca]

There are some helpers but I prefer to call ActiveSupport::Deprecation.warn directly.

[apotonick]

This guy is ready to be merged, @rafaelfranca and @josevalim.

[rafaelfranca]

This method should be private

[rafaelfranca]

We still need tests overriding local_prefixes. Also _prefix is a private method still (because of the _) so I'd not recommend to override it on the CHANGELOG and documentation.

[apotonick]

I added tests for overriding ::local_prefixes, made it private and removed references to _parent_prefixes in the docs. 🎆

[apotonick]

Hi @rafaelfranca - this is ready to be merged, rebased and squashed in https://github.com/apotonick/rails/tree/simplify-prefixes. Thanks ❤️

[apotonick]

Do you want me to push --force rebased/squashed branches to the original PR branch next time, so the commit meta data remains untouched (e.g. pushing simplify-prefixes (the new, squashed branch) to simpler-prefixes (this branch of this PR)?

[apotonick]

Oh, and thanks!

[rafaelfranca]

Yes. For us it is better.

[apotonick]

For me, too!

And again, thanks for this prompt and uncomplicated merge, I really really appreciate the "open-ness" in the core towards architectural changes. ❤️