| name | rails-upgrade-6-to-7 |
| description | Upgrade a Ruby on Rails app from 6.x to 7.x — dual-boot via next_rails, the Zeitwerk autoloader transition (was already in 6.0 but became mandatory), Sprockets-to-importmap or jsbundling decision, Hotwire arriving, encrypted attributes via Active Record Encryption (7.0+), the version hop sequence. Use when the user is upgrading from Rails 6 to 7, mentions Zeitwerk, Webpacker removal, importmap-rails, Hotwire migration, encrypted attributes, or asks how to get off Rails 6. |
Rails 6 → 7 Upgrade
Bigger hop than 7→8. Webpacker is gone. Zeitwerk autoloader is mandatory. Hotwire arrives. Treat it as a multi-week project for a non-trivial app.
The opinion
Dual-boot with next_rails. Hop 6.0 → 6.1 → 7.0 → 7.1. Migrate off Webpacker as a separate project before or after — never inline with the version bump. Choose importmap-rails (default) or jsbundling-rails based on app size. Adopt Hotwire (Turbo+Stimulus) gradually if you have a heavy jQuery legacy.
The hop sequence
6.0 → 6.1 → 7.0 → 7.1
Core patterns
Pattern 1: 6.0 → 6.1
Key changes:
- Multi-DB support (
connects_to).
- Stricter
enum semantics.
where.missing(:assoc) shortcut.delegated_type shipped.
Hop, fix deprecations, ship.
Pattern 2: 6.1 → 7.0 — the big one
Required:
- Ruby 2.7+.
- Zeitwerk autoloader (was already in 6.0 as default — but 7.0 removes Classic).
Breaking-ish:
- Webpacker deprecated; replaced by importmap-rails or jsbundling-rails (esbuild / rollup / webpack still available).
- spring-watcher-listen removed.
- ActiveRecord Encryption ships (
encrypts :col).
Webpacker decision matrix:
| App | Pick |
|---|
| Server-rendered Rails + sprinkle of JS | importmap-rails (no Node build) |
| React/Vue SPA mixed in | jsbundling-rails with esbuild |
| Heavy CSS preprocessing | cssbundling-rails |
| Legacy Webpacker app, can't migrate yet | shakapacker (community fork) |
gem "importmap-rails"
Pattern 3: 7.0 → 7.1
Key changes:
Rails.error.report arrives.async_count, load_async.- Trilogy gem for MySQL.
composed_of deprecated; use Attributes API.
Mild hop; mostly deprecation cleanup.
Pattern 4: Hotwire adoption
Rails 7.0 ships Hotwire (turbo-rails, stimulus-rails) by default for new apps. Existing app gets it via:
bin/rails turbo:install
bin/rails stimulus:install
Don't rewrite all your jQuery in one PR. Adopt incrementally: new pages use Turbo Frames; old pages keep jQuery until you have a reason to touch them. See hotwire-turbo-stimulus.
Common mistakes to refuse
- Don't migrate Webpacker → importmap as part of the version bump. Separate project.
- Don't enable Zeitwerk + Rails 7 + Hotwire in the same PR. Stage them.
- Don't skip Rails 6.1.
See also
rails-upgrade-7-to-8 — next hoprails-upgrade-5-to-6 — previous hophotwire-turbo-stimulusasset-pipeline-propshaft
Sources
