Some content types in Whitehall are versioned so that we are able to explain how a content item reached its current state. At time of writing, the versioned content types are:
- Document Editions
- Worldwide Organisations
Versioning behaviour is implemented in the audit trail module.
Every time an auditable model is created or updated, the audit trail module adds a new record to the versions table. The version data includes the type and ID of the auditable model, the user ID of the user who triggered the event, if available (for updates performed via Rake tasks or queue workers this may not be possible), the new state of the model, and a timestamp. Note that user IDs are tracked in the whodunnit column, which is an idea borrowed from the Paper Trail rails gem.
The whodunnit value is populated by fetching the user from the Current model. The Current model extends the Active Support CurrentAttributes class, which provides convenient access to global request data in a thread-safe manner.
# Get the latest version of an edition
edition.versions.last
#<Version:0x00007f237b75bd40 id: 6796161, item_type: "Edition", item_id: 853413, event: "update", whodunnit: "xxx", object: nil, created_at: Fri, 09 Dec 2022 10:51:41.000000000 GMT +00:00, state: "published"># Get the previous version from a version
versions.previous
#<Version:0x00007f237b75bd40 id: 6618274, item_type: "Edition", item_id: 853413, event: "update", whodunnit: "xxx", object: nil, created_at: Fri, 02 Dec 2022 10:51:41.000000000 GMT +00:00, state: "published">