fix(flags): align presence operator semantics

[marandaneto]

💡 Motivation and Context

sdk-specs PR #49 defines is_not_set using partial property context. The Ruby local evaluator raised an inconclusive error even when the caller supplied the property key.

This change returns false for is_not_set whenever the key is present, including nil and other falsey values. An omitted key remains inconclusive.

💚 How did you test it?

• Ruby syntax checks for the implementation and spec
• Direct smoke checks for present and omitted property behavior
• pnpm changeset status (patches posthog-ruby and posthog-rails)
• Autoreview completed on commit 39e05e1 with no actionable findings.

RSpec was not run locally because bundled dependencies were unavailable. CI will run the complete test suite.

📝 Checklist

• I reviewed the submitted code.
• I added tests to verify the changes.
• I updated the docs if needed.
• No breaking change or entry added to the changelog.

If releasing new changes

• Ran pnpm changeset to generate a changeset file

🤖 Agent context

Autonomy: Human-driven (agent-assisted)

Pi coding agent worker subagents implemented the focused matcher change and regression specs. The bundled autoreview tool reviewed the final committed diff against origin/main.

[github-actions]

posthog-ruby Compliance Report

Date: 2026-08-26 09:53:11 UTC
Duration: 98007ms

✅ All Tests Passed!

46/46 tests passed

---

Capture Tests

✅ 29/29 tests passed

View Details

Test	Status	Duration
Format Validation.Event Has Required Fields	✅	108ms
Format Validation.Event Has Uuid	✅	105ms
Format Validation.Event Has Lib Properties	✅	107ms
Format Validation.Distinct Id Is String	✅	106ms
Format Validation.Token Is Present	✅	105ms
Format Validation.Custom Properties Preserved	✅	106ms
Format Validation.Event Has Timestamp	✅	106ms
Retry Behavior.Retries On 503	✅	5313ms
Retry Behavior.Does Not Retry On 400	✅	2107ms
Retry Behavior.Does Not Retry On 401	✅	2108ms
Retry Behavior.Respects Retry After Header	✅	8014ms
Retry Behavior.Implements Backoff	✅	15509ms
Retry Behavior.Retries On 500	✅	5212ms
Retry Behavior.Retries On 502	✅	5209ms
Retry Behavior.Retries On 504	✅	5211ms
Retry Behavior.Max Retries Respected	✅	15521ms
Deduplication.Generates Unique Uuids	✅	109ms
Deduplication.Preserves Uuid On Retry	✅	5210ms
Deduplication.Preserves Uuid And Timestamp On Retry	✅	10409ms
Deduplication.Preserves Uuid And Timestamp On Batch Retry	✅	5214ms
Deduplication.No Duplicate Events In Batch	✅	110ms
Deduplication.Different Events Have Different Uuids	✅	106ms
Compression.Sends Gzip When Enabled	✅	105ms
Batch Format.Uses Proper Batch Structure	✅	105ms
Batch Format.Flush With No Events Sends Nothing	✅	3ms
Batch Format.Multiple Events Batched Together	✅	109ms
Error Handling.Does Not Retry On 403	✅	2107ms
Error Handling.Does Not Retry On 413	✅	2107ms
Error Handling.Retries On 408	✅	5211ms

Feature_Flags Tests

✅ 17/17 tests passed

View Details

Test	Status	Duration
Request Payload.Request With Person Properties Device Id	✅	106ms
Request Payload.Flags Request Uses V2 Query Param	✅	106ms
Request Payload.Flags Request Hits Flags Path Not Decide	✅	106ms
Request Payload.Flags Request Omits Authorization Header	✅	107ms
Request Payload.Token In Flags Body Matches Init	✅	107ms
Request Payload.Groups Round Trip	✅	106ms
Request Payload.Groups Default To Empty Object	✅	106ms
Request Payload.Disable Geoip False Propagates As Geoip Disable False	✅	106ms
Request Payload.Disable Geoip Omitted Defaults To False	✅	106ms
Request Payload.Flag Keys To Evaluate Contains Only Requested Key	✅	106ms
Request Lifecycle.No Flags Request On Init Alone	✅	2ms
Request Lifecycle.No Flags Request On Normal Capture	✅	105ms
Request Lifecycle.Two Flag Calls Produce Two Remote Requests	✅	109ms
Request Lifecycle.Mock Response Value Is Returned To Caller	✅	105ms
Retry Behavior.Retries Flags On 502	✅	256ms
Retry Behavior.Retries Flags On 504	✅	208ms
Side Effect Events.Get Feature Flag Captures Feature Flag Called Event	✅	108ms

[greptile-apps]

_{Reviews (1): Last reviewed commit: "chore: include Rails in changeset" | Re-trigger Greptile}