File: add validation for path uniqueness

Author: kkoehn

app/models/code_ocean/file.rb

@@ -60,6 +60,8 @@ class File < ApplicationRecord
     validates :weight, absence: true, unless: :teacher_defined_assessment?
     validates :file, presence: true if :context.is_a?(Submission)
     validates :context_type, inclusion: {in: ALLOWED_CONTEXT_TYPES}
+    validates :path, uniqueness: {scope: %I[name file_type context_id context_type role]}
+
     # xml_id_path must be unique within the scope of an exercise.
     # Initially, it may match the record’s id (set while exporting),
     # but it can later diverge as long as uniqueness is preserved.

spec/models/code_ocean/file_spec.rb

@@ -137,4 +137,18 @@
       end
     end
   end
+
+  context 'when a file with same attributes (path, name file_type context_id context_type role) already exists' do
+    before do
+      create(:file, name: 'static', context: exercise)
+      file.validate
+    end
+
+    let(:exercise) { create(:dummy) }
+    let(:file) { build(:file, name: 'static', context: exercise) }
+
+    it 'has an error for path' do
+      expect(file.errors[:path]).to be_present
+    end
+  end
 end