Publish factory_bot.compile_factory notification

Related to [comment on #1586][]
---

Publish Active Support Notifications under the
`factory_bot.compile_factory` key.

They payload for that event is a `Hash` with keys:

* `name:` - the name of the Factory
* `class:` - the Ruby class the Factory constructs instances of
* `attributes:` - a `FactoryBot::AttributesList` instance for the available
  attributes
* `traits:` - an Array of `FactoryBot::Trait` instances for the available
  traits

[comment on #1586]: #1586 (comment)

GETTING_STARTED.md

@@ -1990,7 +1990,7 @@ ActiveSupport Instrumentation
 
 In order to track what factories are created (and with what build strategy),
 `ActiveSupport::Notifications` are included to provide a way to subscribe to
-factories being run. One example would be to track factories based on a
+factories being compiled and run. One example would be to track factories based on a
 threshold of execution time.
 
 ```ruby
@@ -2024,6 +2024,29 @@ config.after(:suite) do
 end
 ```
 
+Another example could involve tracking the attributes and traits that factories are compiled with. If you're using RSpec, you could add `before(:suite)` and `after(:suite)` blocks that subscribe to `factory_bot.compile_factory` notifications:
+
+```ruby
+factory_bot_results = {}
+config.before(:suite) do
+  ActiveSupport::Notifications.subscribe("factory_bot.compile_factory") do |name, start, finish, id, payload|
+    factory_name = payload[:name]
+    factory_class = payload[:class]
+    attributes = payload[:attributes]
+    traits = payload[:traits]
+    factory_bot_results[factory_class] ||= {}
+    factory_bot_results[factory_class][factory_name] = {
+      attributes: attributes.map(&:name)
+      traits: traits.map(&:name)
+    }
+  end
+end
+
+config.after(:suite) do
+  puts factory_bot_results
+end
+```
+
 Rails Preloaders and RSpec
 --------------------------
 

docs/src/activesupport-instrumentation/summary.md

@@ -2,7 +2,7 @@
 
 In order to track what factories are created (and with what build strategy),
 `ActiveSupport::Notifications` are included to provide a way to subscribe to
-factories being run. One example would be to track factories based on a
+factories being compiled and run. One example would be to track factories based on a
 threshold of execution time.
 
 ```ruby
@@ -35,3 +35,26 @@ config.after(:suite) do
   puts factory_bot_results
 end
 ```
+
+Another example could involve tracking the attributes and traits that factories are compiled with. If you're using RSpec, you could add `before(:suite)` and `after(:suite)` blocks that subscribe to `factory_bot.compile_factory` notifications:
+
+```ruby
+factory_bot_results = {}
+config.before(:suite) do
+  ActiveSupport::Notifications.subscribe("factory_bot.compile_factory") do |name, start, finish, id, payload|
+    factory_name = payload[:name]
+    factory_class = payload[:class]
+    attributes = payload[:attributes]
+    traits = payload[:traits]
+    factory_bot_results[factory_class] ||= {}
+    factory_bot_results[factory_class][factory_name] = {
+      attributes: attributes.map(&:name)
+      traits: traits.map(&:name)
+    }
+  end
+end
+
+config.after(:suite) do
+  puts factory_bot_results
+end
+```

lib/factory_bot/definition.rb

@@ -57,6 +57,13 @@ def compile(klass = nil)
         end
 
         @compiled = true
+
+        ActiveSupport::Notifications.instrument "factory_bot.compile_factory", {
+          name: name,
+          attributes: declarations.attributes,
+          traits: defined_traits,
+          class: klass
+        }
       end
     end
 

spec/acceptance/activesupport_instrumentation_spec.rb

@@ -11,7 +11,7 @@ def subscribed(callback, *args)
   ActiveSupport::Notifications.extend SubscribedBehavior
 end
 
-describe "using ActiveSupport::Instrumentation to track factory interaction" do
+describe "using ActiveSupport::Instrumentation to track run_factory interaction" do
   let(:slow_user_factory) { FactoryBot::Internal.factory_by_name("slow_user") }
   let(:user_factory) { FactoryBot::Internal.factory_by_name("user") }
   before do
@@ -78,3 +78,45 @@ def subscribed(callback, *args)
     expect(tracked_invocations[:user][:create]).to eq(5)
   end
 end
+
+describe "using ActiveSupport::Instrumentation to track compile_factory interaction" do
+  before do
+    define_model("User", name: :string, email: :string)
+
+    FactoryBot.define do
+      factory :user do
+        sequence(:email) { |n| "user_#{n}@example.com" }
+
+        name { "User" }
+
+        trait :special do
+          name { "Special User" }
+        end
+      end
+    end
+  end
+
+  it "tracks proper time of compiling the factory" do
+    time_to_execute = 0
+    callback = ->(_name, start, finish, _id, _payload) { time_to_execute = finish - start }
+    ActiveSupport::Notifications.subscribed(callback, "factory_bot.compile_factory") do
+      FactoryBot.build(:user)
+    end
+
+    expect(time_to_execute).to be > 0
+  end
+
+  it "builds the correct payload" do
+    tracked_payloads = []
+    callback = ->(_name, _start, _finish, _id, payload) { tracked_payloads << payload }
+
+    ActiveSupport::Notifications.subscribed(callback, "factory_bot.compile_factory") do
+      FactoryBot.build(:user)
+    end
+
+    payload = tracked_payloads.detect { |payload| payload[:name] == :user }
+    expect(payload[:class]).to eq(User)
+    expect(payload[:attributes].map(&:name)).to eq([:email, :name])
+    expect(payload[:traits].map(&:name)).to eq(["special"])
+  end
+end