Stop preconditions from being executed twice (#130)

CHANGELOG.md

@@ -1,5 +1,9 @@
 ## Next
 
+## v0.17.3
+
+* Stopped preconditions from being executed twice on `#try_perform!`
+
 ## v0.17.2
 
 * Deprecate `Granite::Action#perform` in favor of using `Granite::Action#try_perform!`, as these 2 methods are basically identical. It will be removed in next major version. (https://github.com/toptal/granite/pull/117)

lib/granite/action/performing.rb

@@ -79,7 +79,7 @@ def perform!(context: nil, **options)
       # @raise [Granite::Action::ValidationError] Action or associated objects are invalid
       # @raise [NotImplementedError] execute_perform! method was not defined yet
       def try_perform!(context: nil, **options)
-        return unless satisfy_preconditions?
+        return unless satisfy_preconditions?(cache_result: true)
 
         transaction do
           validate!(context)

lib/granite/action/preconditions.rb

@@ -85,16 +85,17 @@ def add_precondition(klass, *args, &block)
 
       def initialize(*)
         @failed_preconditions = []
+        @preconditions_run = nil
         super
       end
 
       # Check if all preconditions are satisfied
       #
       # @return [Boolean] wheter all preconditions are satisfied
-      def satisfy_preconditions?
+      def satisfy_preconditions?(cache_result: false)
         errors.clear
         failed_preconditions.clear
-        run_preconditions!
+        run_preconditions!(cache_result: cache_result)
       end
 
       # Adds passed error message and options to `errors` object
@@ -105,8 +106,9 @@ def decline_with(*args, **kwargs)
 
       private
 
-      def run_preconditions!
-        _preconditions.execute! self
+      def run_preconditions!(cache_result: false)
+        _preconditions.execute!(self) if @preconditions_run.nil?
+        @preconditions_run = true if cache_result
         errors.empty?
       end
 

lib/granite/version.rb

@@ -1,3 +1,3 @@
 module Granite
-  VERSION = '0.17.2'.freeze
+  VERSION = '0.17.3'.freeze
 end

spec/lib/granite/action/performing_spec.rb

@@ -322,6 +322,37 @@ def execute_perform!(*)
   end
 
   describe '#try_perform!' do
+    context 'when checking preconditions run count' do
+      let(:action) { Action.new(user) }
+
+      before do
+        stub_class(:action, Granite::Action) do
+          subject :user, class_name: 'DummyUser'
+
+          allow_if { true }
+
+          attr_accessor :preconditions_run_count
+
+          precondition do
+            @preconditions_run_count ||= 0
+            @preconditions_run_count += 1
+          end
+
+          private
+
+          def execute_perform!(*)
+            false
+          end
+        end
+      end
+
+      it 'runs preconditions only once' do
+        action.try_perform!
+
+        expect(action.preconditions_run_count).to eq(1)
+      end
+    end
+
     context 'with login' do
       let(:action) { Action.new(user, login: 'Login') }