Fix serialization of zero-parameter events in raw_events

[DZakh]

Summary

Fixes a regression where zero-parameter events were not being serialized correctly for the raw_events table. The native decoder returns an empty object {} for events with no parameters, but the raw_events table expects null for the params field.

Changes

• EventConfigBuilder.res: Updated buildParamsSchema to use a transform serializer that converts any decoded value (including {}) to null for zero-parameter events, instead of relying on a magic cast that didn't properly handle serialization.

• MockIndexer.res: Updated test helper configurations to use EventConfigBuilder.buildParamsSchema([]) and EventConfigBuilder.buildSimulateParamsSchema([]) instead of manually constructing schemas with magic casts, ensuring consistency with the fixed implementation.

• HyperSyncDecoder_test.res: Added regression test that verifies toRawEvent correctly serializes empty params decoded by the native decoder without crashing the batch write.

Implementation Details

The fix uses S.transform with a serializer function to ensure that regardless of what value the decoder produces for zero-parameter events, it gets serialized as null in the raw_events table. This maintains the contract that raw_events stores null for events with no parameters while allowing the decoder to emit {}.

https://claude.ai/code/session_01WNLV8wTTY4D4mJmSTvkf4m

Summary by CodeRabbit

• Bug Fixes

  • Improved event serialization so events with no decoded parameters are now represented consistently in raw event payloads.
  • Preserved existing behavior for events that do include parameters.

• Tests

  • Added a regression test covering zero-parameter event decoding and raw event output formatting.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: fd3afd96-5019-4206-836d-7890e061ebab

📥 Commits

Reviewing files that changed from the base of the PR and between 4697df2 and c5b919c.

📒 Files selected for processing (1)

• packages/envio/src/sources/Evm.res

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📝 Walkthrough

Walkthrough

toRawEvent in Evm.res now checks eventConfig.paramsMetadata length and passes unit (serialized as "null") for zero-parameter events instead of payload.params. MockIndexer.res replaces hardcoded S.literal(null)/S.unknown schemas with EventConfigBuilder.buildParamsSchema([])/buildSimulateParamsSchema([]). A regression test verifies the params: "null" output for an Empty event.

Changes

Zero-param event params serialization fix

Layer / File(s)	Summary
toRawEvent conditional null serialization packages/envio/src/sources/Evm.res	Derives eventConfig from eventItem.eventConfig and conditionally passes unit for zero-parameter events or payload.params otherwise when building RawEvent.
MockIndexer empty-params schemas scenarios/test_codegen/test/helpers/MockIndexer.res	Replaces hardcoded S.literal(null)/S.unknown schemas with EventConfigBuilder.buildParamsSchema([]) and buildSimulateParamsSchema([]) in event construction and evmEventConfig.
Regression test scenarios/test_codegen/test/lib_tests/HyperSyncDecoder_test.res	Adds a Vitest test decoding an Empty event and asserting toRawEvent serializes params as %raw("null").

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Possibly related issues

• raw_events: true crashes batch write for zero-parameter events ("Expected undefined, received {}") #1353: Directly addresses the same zero-parameter raw-event serialization path that this PR fixes.

Possibly related PRs

• enviodev/hyperindex#1335: Introduced the ecosystem-pluggable toRawEvent in Evm.res that this PR extends with zero-params handling.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly matches the main change: fixing raw_events serialization for zero-parameter events.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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