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[go_router] Cannot distinguish a blocked initial deep link from other routing errors in onException #189581
Description
Use case
Apps using onEnter for async guards (entitlements, permissions, feature flags) sometimes need to block the very first navigation — e.g. a deep link on web arrives before the guard's data is cached, so onEnter returns Block.stop().
When that happens there is no prior route to restore, and the parser reports a generic GoException('Navigation to ... was blocked by onEnter with no prior route to restore') through onException. The app wants to recover differently depending on the cause: redirect a blocked deep link to a loading screen with the original location preserved, but send genuine 404s and other routing errors to a fallback screen. Today the only way to tell them apart is string matching on the exception message, which breaks silently if the message ever changes.
Proposal
Add a typed BlockedInitialNavigationException extends GoException, raised in that specific code path. Existing is GoException checks keep working; apps can opt into if (state.error is BlockedInitialNavigationException) in onException.
Activity
mbcorona commentedon Jul 16, 2026
Thanks for the proposal and linked PR.
Routing to the framework team; PR flutter/packages#12213 is linked. Related to #189582.
[go_router] Add BlockedInitialNavigationException for blocked initial…
github-actions commentedon Aug 12, 2026
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flutter doctor -vand a minimal reproduction of the issue.