This change conditionally renders the TurboOffline caching rules based on
whether the request comes from a Hotwire Native app. Web browsers get a
minimal service worker that only handles push notifications and a simple
document fetch fallback.
Why separate behavior for native vs web?
-----------------------------------------
We want offline caching for Hotwire Native apps (where users expect
app-like offline behavior) but not for regular web browsers.
Why use ERB conditional rendering?
----------------------------------
We explored several approaches to detect Hotwire Native requests in the
service worker:
1. User-Agent detection in fetch handler: Would be ideal, but Android
WebViews override the User-Agent header with the system default when
requests are intercepted by service workers, stripping the custom
"Hotwire Native" identifier.
2. Custom header (X-Hotwire-Native) from native apps: Would require
intercepting ALL requests at the native level using both
WebViewClient.shouldInterceptRequest() and ServiceWorkerClient.
Complex to implement and still incomplete coverage for all request
types (navigation, resources loaded by HTML).
3. In-memory flag with IndexedDB persistence: Service workers can be
terminated when idle and restart with fresh state. Reading from
IndexedDB is async, but the decision to call respondWith() in a
fetch handler must be synchronous.
4. Separate service worker URLs: Same theoretical churn problem as ERB
rendering, with more complexity.
Why ERB conditional rendering works in practice
-----------------------------------------------
The main concern with conditional ERB rendering was "churn" — the service
worker constantly updating as different client types fetch it. However,
this only happens when web and native share storage on the same device.
In practice, this is rare because:
- Android native apps use isolated WebView storage
- iOS doesn't support service workers in WebViews (yet)
- Web browsers have completely separate storage
So each context gets its own stable service worker without churn.
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
Rosa Gutierrez
975968b50f