Add rake tasks to manage features

[kevinnio]

Hey guys, I noticed Flipflop doesn't have a way to manage features via console out of the box, so here's this PR built from work I had to do in one of my projects.

This adds a set of rake tasks that allow the user to control features the same way they can currently do it in the Dashboard.

These are the new tasks:

rake flipflop:features                    # Shows features table
rake flipflop:turn_on[feature,strategy]   # Enables a feature with the specified strategy
rake flipflop:turn_off[feature,strategy]  # Disables a feature with the specified strategy

For example, let's say you have a config/features.rb file like this:

Flipflop.configure do
  strategy :cookie
  strategy :active_record
  strategy :default

  feature :world_domination, default: false
  feature :peace_among_worlds, default: false
end

To enable :peace_among_worlds using :active_record you would do:

bundle exec rake flipflop:turn_on[peace_among_worlds,active_record]
# => Feature :peace_among_worlds enabled!

To disable :world_domination using :cookie you would do:

bundle exec rake flipflop:turn_off[world_domination,cookie]
# => Feature :world_domination disabled!

To see the current state of your features you would do:

bundle exec rake flipflop:features

# => ┌──────────────────┬───────────┬──────┬─────────────┬───────┐
# => │feature           │description│cookie│active_record│default│
# => ├──────────────────┼───────────┼──────┼─────────────┼───────┤
# => │world_domination  │           │OFF   │             │OFF    │
# => ├──────────────────┼───────────┼──────┼─────────────┼───────┤
# => │peace_among_worlds│           │      │ON           │OFF    │
# => └──────────────────┴───────────┴──────┴─────────────┴───────┘

Thanks for such a great gem, guys!

[kevinnio]

@rolftimmermans If you could do a quick review of this, I'll appreciate it. There's also #27 waiting for review. 😉

[rolftimmermans]

Love this idea! I wonder how to deal with strategies that cannot be changed via the console though, especially those that require a request context (like session & cookie strategies).

Another concern I have is the new gem dependency; I prefer to have minimal dependencies where possible; tty-table brings in 5 more gem dependencies on its own.

Anyway, I would love to see this implemented so if you have any thoughts on this I would love to hear it!

[kevinnio]

Thanks for the quick reply, @rolftimmermans.

I added tty-table as a dependency to render the features table more easily, but I guess I can found another way to do it without introducing so many new gems to the project.

About the other strategies, I originally built this for a project that was using only :default and :active_record so I didn't pay much attention to non-switchable ones like :lambda or the ones that depend on request. From the top of my head I'd say we exclude such strategies from console management, but I want to review the code and see if I can make this work somehow. I'll post an update later this week.

[rolftimmermans]

Just looked at the code for the strategies in more detail and it seems all request-based strategies will default to nil for all features when no request is present. So there is no immediate need to exclude them. Also the switchable? method will return false so if you check that before attempting to set a feature value (and display an error appropriately) then everything should be fine.

[kevinnio]

@rolftimmermans I replaced tty-table with the most lightweight replacement I could find. Also added a check for switchable?.

What do you think?

[rolftimmermans]

Starting to look good. The only remaining comment I have when looking at the code is that features are 'ternary' – they can be explicitly enabled (true), explicitly disabled (false) or unset (nil) by a strategy. If you look at the dashboard you see that they can be on/off, or cleared. Right now the code only checks for truthiness but I think it should display one of three states, perhaps ON for true, OFF for false and - for nil. Does that make sense?

[kevinnio]

Yeah, totally makes sense. I'll check for nil and produce the respective output.

By the way, do you think adding a rake flipflop:unset[feature,strategy] is a good idea?

[rolftimmermans]

Unsetting/clearing does seem potentially useful. I think the dashboard refers to this as clearing a feature.

[kevinnio]

OK, then. I'll add a rake flipflop:clear[feature,strategy] task as soon as I can. Thanks.

[kevinnio]

Added the clear task. Working on some unit tests for all of this...

[rolftimmermans]

LGTM. Would you say it's ready?

[kevinnio]

Yeah, totally. Ready to merge whenever you are!