2809: Merge branch 'master' into 2809-workbench-rails4 refs #2809

[arvados.git] / services / api / lib / can_be_an_owner.rb

diff --git a/services/api/lib/can_be_an_owner.rb b/services/api/lib/can_be_an_owner.rb
new file mode 100644 (file)
index 0000000..16a8783
--- /dev/null
+++ b/services/api/lib/can_be_an_owner.rb
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+# Protect referential integrity of owner_uuid columns in other tables
+# that can refer to the uuid column in this table.
+
+module CanBeAnOwner
+
+  def self.included(base)
+    # Rails' "has_many" can prevent us from destroying the owner
+    # record when other objects refer to it.
+    ActiveRecord::Base.connection.tables.each do |t|
+      next if t == base.table_name
+      next if t == 'schema_migrations'
+      klass = t.classify.constantize
+      next unless klass and 'owner_uuid'.in?(klass.columns.collect(&:name))
+      base.has_many(t.to_sym,
+                    foreign_key: :owner_uuid,
+                    primary_key: :uuid,
+                    dependent: :restrict)
+    end
+    # We need custom protection for changing an owner's primary
+    # key. (Apart from this restriction, admins are allowed to change
+    # UUIDs.)
+    base.validate :restrict_uuid_change_breaking_associations
+  end
+
+  protected
+
+  def restrict_uuid_change_breaking_associations
+    return true if new_record? or not uuid_changed?
+
+    # Check for objects that have my old uuid listed as their owner.
+    self.class.reflect_on_all_associations(:has_many).each do |assoc|
+      next unless assoc.foreign_key == :owner_uuid
+      if assoc.klass.where(owner_uuid: uuid_was).any?
+        errors.add(:uuid,
+                   "cannot be changed on a #{self.class} that owns objects")
+        return false
+      end
+    end
+
+    # if I owned myself before, I'll just continue to own myself with
+    # my new uuid.
+    if owner_uuid == uuid_was
+      self.owner_uuid = uuid
+    end
+  end
+
+end