Fix effect cache returning nested-option sentinel for None

[DZakh]

Summary

Fixes a regression in envio v3.1.0-rc.x where effects with optional outputs that resolve to None would leak the ReScript nested-option sentinel { BS_PRIVATE_NESTED_SOME_NONE: 0 } instead of undefined when served from the in-memory cache.

Root Cause

The in-memory effect cache stores option<output> for all effects. When an effect with optional output (e.g., option<bigint>) returns None, the cache stores Some(None). On cache hits, the code was wrapping this cached value in another Option.getUnsafe, which returned the raw Some(None) to the handler instead of unwrapping it to None/undefined.

Key Changes

• InMemoryStore.res: Split getEffectOutput into two functions:

  • hasEffectOutput: Checks cache presence without wrapping the result
  • getEffectOutputUnsafe: Returns the raw cached output directly (never wrapped in Option), preventing the nested-option sentinel from leaking

• LoadLayer.res: Updated cache access to use the new functions, eliminating the extra Option wrapping that was causing the regression

• LoadLayer_test.res: Added regression test verifying that optional outputs resolving to None return undefined (not the sentinel) on cache hits

Implementation Details

The fix ensures the cache hit path mirrors the cache miss path: both return the raw effect output without additional option wrapping. For effects with optional outputs, None is now correctly represented as undefined in both paths.

https://claude.ai/code/session_01QV6rPnY9qR7RubvyACNUdb

Summary by CodeRabbit

• Bug Fixes

  • Fixed in-memory effect output caching for optional types, addressing a regression in handling cached outputs.

• Tests

  • Added test suite to verify effect cache behavior with optional outputs and ensure handlers execute only once on cache hits.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

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Run ID: c68d21b6-8056-47a1-8f07-22022e80da31

📥 Commits

Reviewing files that changed from the base of the PR and between 8b446eb and b070a3b.

📒 Files selected for processing (3)

• packages/envio/src/InMemoryStore.res
• packages/envio/src/LoadLayer.res
• scenarios/test_codegen/test/LoadLayer_test.res

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📝 Walkthrough

Walkthrough

This PR fixes a regression in envio v3.1.0-rc.x where optional effect outputs were incorrectly cached. The in-memory store's cache API was refactored from Option-based access to sentinel-based undefined values, LoadLayer was updated to use the new API, and a regression test was added.

Changes

Effect cache optional output handling

Layer / File(s)	Summary
InMemoryStore effect cache API refactor packages/envio/src/InMemoryStore.res	Introduced hasEffectOutput for presence checks and replaced getEffectOutput (returning option<effectOutput>) with getEffectOutputUnsafe (returning raw effectOutput with delete/absence mapped to %raw(\undefined`)` sentinel).
LoadLayer cache integration update packages/envio/src/LoadLayer.res	loadEffect now uses InMemoryStore.getEffectOutputUnsafe and InMemoryStore.hasEffectOutput for cache access, replacing the prior Option.getUnsafe and Option.isSome patterns.
Effect cache optional output regression test scenarios/test_codegen/test/LoadLayer_test.res	New test suite LoadLayer effect cache validates that effects returning option types are cached correctly; defines an effect with option<bigint> output returning None, calls loadEffect twice with the same inputs, and asserts both results are None with the handler running exactly once.

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🎯 2 (Simple) | ⏱️ ~12 minutes

🚥 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 directly and specifically describes the main fix in the changeset: addressing an effect cache bug where optional outputs resolving to None incorrectly return a nested-option sentinel instead of undefined.
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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