change Bullet's feature enable logic

[koya1616]

fix #703

This pull request includes changes to the lib/bullet.rb file to improve the handling of feature enablement flags by introducing default values and refactoring the enablement checks.

Refactoring of feature enablement flags:

• lib/bullet.rb: Modified the enable= method to set default values for @n_plus_one_query_enable, @unused_eager_loading_enable, and @counter_cache_enable if they are not already set.
• lib/bullet.rb: Refactored the n_plus_one_query_enable?, unused_eager_loading_enable?, and counter_cache_enable? methods to use new helper methods (default_n_plus_one_query_enable?, default_unused_eager_loading_enable?, and default_counter_cache_enable?) for checking the default values.

---

Note: When calling Bullet.enable, all other detectors are reset to their defaults (true) and need reconfiguring.

Is there any reason why it is set up this?

If there isn't any special reason, I think @n_plus_one_query_enable, @unused_eager_loading_enable, and @counter_cache_enable don't need to be reset. Since there's an enable? && check in the function below, it seems there wouldn't be any impact.

• def n_plus_one_query_enable?
• def unused_eager_loading_enable?
• def counter_cache_enable?

[flyerhzm]

@koya1616 looks like a good solution, but it broke the tests, please take a look.

[koya1616]

@flyerhzm
Thanks!
I fixed it - can you take a look?

[flyerhzm]

@koya1616 this confused me, does it always set these three instance variables to true?

[koya1616]

@flyerhzm
I’m sorry, I misunderstood. I’ve updated it so that it only returns true when the value is nil.

@n_plus_one_query_enable = true if @n_plus_one_query_enable.nil?
@unused_eager_loading_enable = true if @unused_eager_loading_enable.nil?
@counter_cache_enable = true if @counter_cache_enable.nil?

[flyerhzm]

I don't like this way, it's confused that we set @n_plus_one_query_enable = true when we call Bullet.enable = false.

what about giving the instance variable a default value, so that we don't need to do it in enable= method.

  class << self
    @n_plus_one_query_enable = true
  end

[koya1616]

Thanks!
It seems there are cases, as you suggested in your writing style, where class instance variables such as @n_plus_one_query_enable defined within a class << self block are not properly initialized.
As a solution, I'm thinking of creating an initialization method and calling that method to initialize them.
Where do you think I should call this function from? Or is there another better approach?

def initialize_detectors
  @n_plus_one_query_enable = true
  @unused_eager_loading_enable = true
  @counter_cache_enable = true
end