Fix schema migration loading from temporary working dir in dev_dump (t…

…hewca#8303)

WcaOnRails/lib/db_dump_helper.rb

@@ -21,6 +21,22 @@ module DbDumpHelper
   def self.dump_developer_db
     Dir.mktmpdir do |dir|
       FileUtils.cd dir do
+        # WARNING: Headache ahead! By using Rails-DSL database schema files, the migrations in the dev export can break.
+        #   Rails uses the timestamp at the top of the schema file to determine which migration is the latest one.
+        #   It then proceeds to glob the migration folder for older migrations and inserts them when loading the schema.
+        #   However, this glob is _relative_ to the Rails root. Due to our chdir into a temporary directory (where we can
+        #   write files to our heart's desire) the glob returns an empty list. So we symlink the migrations into our tmp
+        #   working directory to make sure that Rails can find them when loading/dumping the schema.
+        primary_connection = ActiveRecord::Base.connection
+        migration_paths = primary_connection.migration_context.migrations_paths
+
+        migration_paths.each do |migration_path|
+          FileUtils.mkpath(File.dirname(migration_path))
+
+          abs_migrations = File.join(Rails.application.root, migration_path)
+          FileUtils.ln_s abs_migrations, migration_path, verbose: true
+        end
+
         DatabaseDumper.development_dump(DEVELOPER_EXPORT_SQL)
 
         self.zip_and_permalink(DEVELOPER_EXPORT_FOLDER, DEVELOPER_EXPORT_SQL_PERMALINK, nil, DEVELOPER_EXPORT_SQL)

WcaOnRails/lib/tasks/db.rake

@@ -69,7 +69,9 @@ namespace :db do
           LogTask.log_task "Clobbering contents of '#{config.database}' with #{DbDumpHelper::DEVELOPER_EXPORT_SQL}" do
             ActiveRecord::Tasks::DatabaseTasks.drop config
             ActiveRecord::Tasks::DatabaseTasks.create config
-            ActiveRecord::Tasks::DatabaseTasks.load_schema config
+
+            # Explicitly loading the schema is not necessary because the downloaded SQL dump file contains CREATE TABLE
+            # definitions, so if we load the schema here the SOURCE command below would overwrite it anyways
 
             DatabaseDumper.mysql("SOURCE #{DbDumpHelper::DEVELOPER_EXPORT_SQL}", config.database)
           end