[bug] running validations callback so as to prevent post_processing on invalid attachments

lib/paperclip/attachment.rb

@@ -491,14 +491,20 @@ def process_options(options_type, style) #:nodoc:
 
     def post_process(*style_args) #:nodoc:
       return if @queued_for_write[:original].nil?
-
-      instance.run_paperclip_callbacks(:post_process) do
-        instance.run_paperclip_callbacks(:"#{name}_post_process") do
-          post_process_styles(*style_args) if !@options[:check_validity_before_processing] || instance.errors.none?
+      if !@options[:check_validity_before_processing] || check_validity?
+        instance.run_paperclip_callbacks(:post_process) do
+          instance.run_paperclip_callbacks(:"#{name}_post_process") do
+            post_process_styles(*style_args)
+          end
         end
       end
     end
 
+    def check_validity?
+      instance.run_paperclip_callbacks(:"#{name}_validate")
+      instance.errors.none?
+    end
+
     def post_process_styles(*style_args) #:nodoc:
       if styles.include?(:original) && process_style?(:original, style_args)
         post_process_style(:original, styles[:original])

lib/paperclip/has_attached_file.rb

@@ -103,7 +103,7 @@ def add_active_record_callbacks
     def add_paperclip_callbacks
       @klass.send(
         :define_paperclip_callbacks,
-        :post_process, :"#{@name}_post_process"
+        :post_process, :"#{@name}_post_process", :"#{@name}_validate"
       )
     end
 

lib/paperclip/validators.rb

@@ -64,7 +64,7 @@ def validate_before_processing(validator_class, options)
       def create_validating_before_filter(attribute, validator_class, options)
         if_clause = options.delete(:if)
         unless_clause = options.delete(:unless)
-        send(:"before_#{attribute}_post_process", if: if_clause, unless: unless_clause) do |*_args|
+        send(:"before_#{attribute}_validate", if: if_clause, unless: unless_clause) do |*_args|
           validator_class.new(options.dup).validate(self)
         end
       end

spec/paperclip/attachment_spec.rb

@@ -880,6 +880,31 @@ def do_after_all; end
       expect(Paperclip::Thumbnail).not_to receive(:make)
       @dummy.avatar = @file
     end
+
+    it "should not call process hooks if validation fails" do
+      Dummy.class_eval do
+        validates_attachment_content_type :avatar, content_type: 'image/jpeg'
+      end
+      expect(@dummy).not_to receive(:do_before_avatar)
+      expect(@dummy).not_to receive(:do_after_avatar)
+      expect(@dummy).not_to receive(:do_before_all)
+      expect(@dummy).not_to receive(:do_after_all)
+      expect(Paperclip::Thumbnail).not_to receive(:make)
+      @dummy.avatar = @file
+    end
+
+    it "should call process hooks if validation would fail but check validity flag is false" do
+      Dummy.class_eval do
+        validates_attachment_content_type :avatar, content_type: 'image/jpeg'
+      end
+      @dummy.avatar.options[:check_validity_before_processing] = false
+      expect(@dummy).to receive(:do_before_avatar)
+      expect(@dummy).to receive(:do_after_avatar)
+      expect(@dummy).to receive(:do_before_all)
+      expect(@dummy).to receive(:do_after_all)
+      expect(Paperclip::Thumbnail).to receive(:make).and_return(@file)
+      @dummy.avatar = @file
+    end
   end
 
   context "Assigning an attachment" do