Implement file name validation based on path, name, and filetype upon file creation

app/controllers/code_ocean/files_controller.rb

@@ -14,6 +14,21 @@ module CodeOcean
       create_and_respond(object: @file, path: proc { implement_exercise_path(@file.context.exercise, tab: 2) })
     end
 
+    def create_and_respond(options = {})
+      @object = options[:object]
+      respond_to do |format|
+        if @object.save
+          yield if block_given?
+          path = options[:path].try(:call) || @object
+          respond_with_valid_object(format, notice: t('shared.object_created', model: @object.class.model_name.human), path: path, status: :created)
+        else
+          filename = (@object.path || '') + '/' + (@object.name || '') + (@object.file_type.file_extension || '')
+          format.html { redirect_to(options[:path]); flash[:danger] = t('files.error.filename', name: filename) }
+          format.json { render(json: @object.errors, status: :unprocessable_entity) }
+        end
+      end
+    end
+
     def destroy
       @file = CodeOcean::File.find(params[:id])
       authorize!

app/models/code_ocean/file.rb

@@ -2,6 +2,17 @@ require File.expand_path('../../../uploaders/file_uploader', __FILE__)
 require File.expand_path('../../../../lib/active_model/validations/boolean_presence_validator', __FILE__)
 
 module CodeOcean
+
+  class FileNameValidator < ActiveModel::Validator
+    def validate(record)
+      existing_files = File.where(name: record.name, path: record.path, file_type_id: record.file_type_id,
+                                  context_id: record.context_id, context: record.context).to_a
+      unless existing_files.empty?
+        record.errors[:base] << 'Duplicate'
+      end
+    end
+  end
+
   class File < ActiveRecord::Base
     include DefaultValues
 
@@ -44,6 +55,8 @@ module CodeOcean
     validates :weight, if: :teacher_defined_test?, numericality: true, presence: true
     validates :weight, absence: true, unless: :teacher_defined_test?
 
+    validates_with FileNameValidator, fields: [:name, :path, :file_type_id]
+
     ROLES.each do |role|
       define_method("#{role}?") { self.role == role }
     end

config/locales/de.yml

@@ -292,6 +292,8 @@ de:
       teacher_defined_test: Test als Bewertungsgrundlage
       user_defined_file: Benutzerdefinierte Datei
       user_defined_test: Benutzerdefinierter Test
+    error:
+      filename: "Die Datei konnte nicht gespeichert werden, da eine Datei mit dem Namen '%{name}' bereits existiert."
   hints:
     form:
       hints:

config/locales/en.yml

@@ -292,6 +292,8 @@ en:
       teacher_defined_test: Test for Assessment
       user_defined_file: User-defined File
       user_defined_test: User-defined Test
+    error:
+      filename: "The file could not be saved, because another file with the name '%{name}' already exists."
   hints:
     form:
       hints: