Refactor factory calculator (#1770)

* refactor: rewrite FactoryCalculator to be functional
* refactor: rename strategy_calculator.rb to strategy.rb
* refactor: move strategy namespace require statements

Author: vburzynski

lib/factory_bot.rb

@@ -11,12 +11,7 @@
 require "factory_bot/errors"
 require "factory_bot/factory_runner"
 require "factory_bot/strategy_syntax_method_registrar"
-require "factory_bot/strategy_calculator"
-require "factory_bot/strategy/build"
-require "factory_bot/strategy/create"
-require "factory_bot/strategy/attributes_for"
-require "factory_bot/strategy/stub"
-require "factory_bot/strategy/null"
+require "factory_bot/strategy"
 require "factory_bot/registry"
 require "factory_bot/null_factory"
 require "factory_bot/null_object"

lib/factory_bot/factory.rb

@@ -36,14 +36,13 @@ def run(build_strategy, overrides, &block)
 
       compile
 
-      strategy = StrategyCalculator.new(build_strategy).strategy.new
+      strategy = Strategy.lookup_strategy(build_strategy).new
 
       evaluator = evaluator_class.new(strategy, overrides.symbolize_keys)
       attribute_assigner = AttributeAssigner.new(evaluator, build_class, &compiled_constructor)
 
       observer = CallbacksObserver.new(callbacks, evaluator)
-      evaluation =
-        Evaluation.new(evaluator, attribute_assigner, compiled_to_create, observer)
+      evaluation = Evaluation.new(evaluator, attribute_assigner, compiled_to_create, observer)
 
       evaluation.notify(:before_all, nil)
       instance = strategy.result(evaluation).tap(&block)

lib/factory_bot/strategy.rb

@@ -0,0 +1,15 @@
+require "factory_bot/strategy/build"
+require "factory_bot/strategy/create"
+require "factory_bot/strategy/attributes_for"
+require "factory_bot/strategy/stub"
+require "factory_bot/strategy/null"
+
+module FactoryBot
+  module Strategy
+    def self.lookup_strategy(name_or_object)
+      return name_or_object if name_or_object.is_a?(Class)
+
+      FactoryBot::Internal.strategy_by_name(name_or_object)
+    end
+  end
+end

lib/factory_bot/strategy_calculator.rb

@@ -1,24 +1,24 @@
-describe FactoryBot::StrategyCalculator do
+describe FactoryBot::Strategy do
   it "returns the class passed when it is instantiated with a class" do
     strategy = define_class("MyAwesomeClass")
-    calculator = FactoryBot::StrategyCalculator.new(strategy).strategy
+    result = described_class.lookup_strategy(strategy)
 
-    expect(calculator).to eq strategy
+    expect(result).to eq strategy
   end
 
   it "finds the strategy by name when instantiated with a symbol" do
     strategy = define_class("MyAwesomeClass")
     allow(FactoryBot::Internal).to receive(:strategy_by_name).and_return(strategy)
-    FactoryBot::StrategyCalculator.new(:build).strategy
+    described_class.lookup_strategy(:build)
 
     expect(FactoryBot::Internal).to have_received(:strategy_by_name).with(:build)
   end
 
   it "returns the strategy found when instantiated with a symbol" do
     strategy = define_class("MyAwesomeClass")
     allow(FactoryBot::Internal).to receive(:strategy_by_name).and_return(strategy)
-    calculator = FactoryBot::StrategyCalculator.new(:build).strategy
+    result = described_class.lookup_strategy(:build)
 
-    expect(calculator).to eq strategy
+    expect(result).to eq strategy
   end
 end