Remove code for registering callbacks

Before this commit, factory_bot registered default callbacks in a global
registry, and offered a `register_callback` method for registering any
custom callbacks (which would be fired within custom strategies).

The idea here seems to have been that we could check against this global
registry and then raise an error when referring to a callback that was
not registered.

However, nobody ever saw this error because we have always had the line:
`FactoryBot::Internal.register_callback(name)`, which registers
callbacks on the fly whenever they are referred to. (I noticed this when
a [change to default callbacks] accidentally duplicated `after_create`
instead of including `before_create`, and we didn't get any tests
failures.)

We have two options here:

1. Preserve the existing behavior by deleting all the callback
registration code. (That is what this commit does)

2. Change to the code try and capture what I assume was the original
intention. This would be a breaking change, so we would want to
introduce it in a major release. (See #1379)

I prefer preserving the existing behavior because we haven't seen any
issues around this, and making a breaking change for this doesn't seem
worthwhile.

[change to default callbacks]: f82e40c8c5 (diff-c6d30be672f880311a7df0820dc4fb21R12-R14)

lib/factory_bot.rb

@@ -89,4 +89,3 @@ module FactoryBot
 end
 
 FactoryBot::Internal.register_default_strategies
-FactoryBot::Internal.register_default_callbacks

lib/factory_bot/callback.rb

@@ -5,7 +5,6 @@ module FactoryBot
     def initialize(name, block)
       @name  = name.to_sym
       @block = block
-      ensure_valid_callback_name!
     end
 
     def run(instance, evaluator)
@@ -27,13 +26,6 @@ module FactoryBot
 
     private
 
-    def ensure_valid_callback_name!
-      unless FactoryBot::Internal.callback_names.include?(name)
-        raise InvalidCallbackNameError, "#{name} is not a valid callback name. " +
-          "Valid callback names are #{FactoryBot::Internal.callback_names.inspect}"
-      end
-    end
-
     def syntax_runner
       @syntax_runner ||= SyntaxRunner.new
     end

lib/factory_bot/definition.rb

@@ -102,7 +102,6 @@ module FactoryBot
 
     def callback(*names, &block)
       names.each do |name|
-        FactoryBot::Internal.register_callback(name)
         add_callback(Callback.new(name, block))
       end
     end

lib/factory_bot/internal.rb

@@ -4,7 +4,6 @@ module FactoryBot
     class << self
       delegate :after,
                :before,
-               :callback_names,
                :callbacks,
                :constructor,
                :factories,
@@ -87,18 +86,6 @@ module FactoryBot
         register_strategy(:build_stubbed, FactoryBot::Strategy::Stub)
         register_strategy(:null, FactoryBot::Strategy::Null)
       end
-
-      def register_default_callbacks
-        register_callback(:after_create)
-        register_callback(:after_build)
-        register_callback(:after_stub)
-        register_callback(:before_create)
-      end
-
-      def register_callback(name)
-        name = name.to_sym
-        callback_names << name
-      end
     end
   end
 end

lib/factory_bot/reload.rb

@@ -2,7 +2,6 @@ module FactoryBot
   def self.reload
     Internal.reset_configuration
     Internal.register_default_strategies
-    Internal.register_default_callbacks
     find_definitions
   end
 end

spec/factory_bot/callback_spec.rb

@@ -24,16 +24,4 @@ describe FactoryBot::Callback do
     FactoryBot::Callback.new(:after_create, ->(one, two) { ran_with = [one, two] }).run(:one, :two)
     expect(ran_with).to eq [:one, :two]
   end
-
-  it "allows valid callback names to be assigned" do
-    FactoryBot::Internal.callback_names.each do |callback_name|
-      expect { FactoryBot::Callback.new(callback_name, -> {}) }.
-        to_not raise_error
-    end
-  end
-
-  it "raises if an invalid callback name is assigned" do
-    expect { FactoryBot::Callback.new(:magic_fairies, -> {}) }.
-      to raise_error(FactoryBot::InvalidCallbackNameError, /magic_fairies is not a valid callback name/)
-  end
 end