Fail if non-type based event handler is defined in projector#517
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erikrozendaal merged 1 commit intomasterfrom Mar 6, 2026
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Since it is not possible to efficiently query the database for non-typed based event handlers (like `has_attrs(...)`) these are now prohibited for projectors as these event handlers were ignored by the replayer, potentially resulting in bad data in the view schema after a replay. Rewrite the event handler to list all types that must be matched instead.
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Pull request overview
This PR adds a validation to Sequent::Core::Projector that prevents non-type-based event handlers (like is_a(...), has_attrs(...), any(...)) from being defined in projectors. The rationale is that the replayer queries the database by concrete event type, so non-type-based matchers would be silently ignored during replay, potentially leading to inconsistent view state.
Changes:
- Overrides
self.oninProjectorto validate that all arguments areClassinstances before delegating to the parent implementation viasuper. - Adds a spec that verifies an
ArgumentErroris raised when a non-type-based matcher is used in a projector'sonhandler.
Reviewed changes
Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.
| File | Description |
|---|---|
lib/sequent/core/projector.rb |
Adds self.on override that validates all args are Class before calling super |
spec/lib/sequent/core/projector_spec.rb |
Adds test verifying ArgumentError for non-type-based event handlers in projectors |
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Since it is not possible to efficiently query the database for non-typed based event handlers (like
has_attrs(...)) these are now prohibited for projectors as these event handlers were ignored by the replayer, potentially resulting in bad data in the view schema after a replay.Rewrite the event handler to list all types that must be matched instead.