Completely remove old non-structured errors and migrate existing ones.

db/migrate/20181129093207_drop_errors.rb

@@ -0,0 +1,46 @@
+class DropErrors < ActiveRecord::Migration[5.2]
+
+  # define old CodeOcean::Error module so that the migration works
+  module CodeOcean
+    class Error < ApplicationRecord
+      belongs_to :execution_environment
+
+      scope :for_execution_environment, ->(execution_environment) { where(execution_environment_id: execution_environment.id) }
+      scope :grouped_by_message, -> { select('MAX(created_at) AS created_at, MAX(id) AS id, message, COUNT(id) AS count').group(:message).order('count DESC') }
+
+      validates :execution_environment_id, presence: true
+      validates :message, presence: true
+
+      def self.nested_resource?
+        true
+      end
+
+      def to_s
+        id.to_s
+      end
+    end
+  end
+
+
+
+  def change
+
+    puts 'Migrating CodeOcean::Errors to StructuredErrors using RegEx. This might take a (long) while but will return.'
+    submissions_controller = SubmissionsController.new
+
+    # Iterate only over those Errors containing a message and submission_id
+    CodeOcean::Error.where.not(message: [nil, ""]).where.not(submission_id: [nil, ""]).each do |error|
+      raw_output = error.message
+      submission = Submission.find_by(id: error.submission_id)
+
+      # Validate that we have everything we need: the output, the submission and the execution environment
+      next if submission.exercise.execution_environment.blank?
+
+      submissions_controller.instance_variable_set(:@raw_output, raw_output)
+      submissions_controller.instance_variable_set(:@submission, submission)
+      submissions_controller.extract_errors
+    end
+
+    drop_table :errors
+  end
+end