fix(flags): align presence operator semantics

[marandaneto]

💡 Motivation and Context

sdk-specs PR #49 defines is_not_set using partial property context. The Go local evaluator returned an inconclusive error even when the caller supplied the property key, although a present key definitively does not match is_not_set.

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

💚 How did you test it?

• go test ./... -run '^TestMatchPropertyPresenceOperators$'
• go test .
• Autoreview completed with no actionable findings.

📝 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 and validated the matcher change. The bundled autoreview tool reviewed the final committed diff against origin/main.

[github-actions]

posthog-go Compliance Report

Date: 2026-08-26 07:50:55 UTC
Duration: 169195ms

✅ All Tests Passed!

111/111 tests passed

---

Capture_V1 Tests

✅ 94/94 tests passed

View Details

Test	Status	Duration
Endpoint And Method.Targets V1 Endpoint	✅	24ms
Endpoint And Method.Does Not Use Legacy Endpoints	✅	6ms
Required Headers.Has Authorization Bearer Header	✅	5ms
Required Headers.Has Content Type Json	✅	7ms
Required Headers.Has Posthog Sdk Info Format	✅	7ms
Required Headers.Has Posthog Attempt Header	✅	6ms
Required Headers.Has Posthog Request Id	✅	6ms
Required Headers.Has Posthog Request Timestamp	✅	6ms
Required Headers.Has User Agent	✅	6ms
Body Format.Body Has Created At And Batch	✅	6ms
Body Format.No Api Key In Body	✅	6ms
Body Format.No Sent At In Body	✅	6ms
Event Format.Event Has Required Root Fields	✅	6ms
Event Format.Event Uuid Is Valid	✅	6ms
Event Format.Event Timestamp Is Rfc3339	✅	6ms
Event Format.Distinct Id Is String	✅	6ms
Event Format.Distinct Id At Root Not Properties	✅	6ms
Event Format.Custom Properties Preserved	✅	6ms
Event Format.Set Properties Preserved	✅	6ms
Event Format.Set Once Properties Preserved	✅	6ms
Event Format.Groups Properties Preserved	✅	6ms
Event Format.Sdk Generates Uuid If Not Provided	✅	5ms
Event Format.Event Has Required Root Fields Batch	✅	9ms
Event Format.Event Uuid Is Valid Batch	✅	9ms
Event Format.Event Timestamp Is Rfc3339 Batch	✅	8ms
Event Format.Distinct Id Is String Batch	✅	9ms
Event Format.Distinct Id At Root Not Properties Batch	✅	8ms
Event Format.Custom Properties Preserved Batch	✅	8ms
Event Format.Set Properties Preserved Batch	✅	9ms
Event Format.Set Once Properties Preserved Batch	✅	8ms
Event Format.Groups Properties Preserved Batch	✅	19ms
Event Format.Sdk Generates Uuid If Not Provided Batch	✅	10ms
Batch Behavior.Multiple Events In Single Batch	✅	29ms
Batch Behavior.Batch Envelope Smoke	✅	10ms
Batch Behavior.Flush With No Events Sends Nothing	✅	4ms
Batch Behavior.Flush At Triggers Batch	✅	1007ms
Batch Behavior.Created At Reflects Batch Creation Time	✅	7ms
Deduplication.Generates Unique Uuids	✅	15ms
Deduplication.Different Events Same Content Different Uuids	✅	9ms
Deduplication.Preserves Uuid On Retry	✅	5135ms
Deduplication.Preserves Timestamp On Retry	✅	5133ms
Deduplication.Preserves Uuid And Timestamp On Batch Retry	✅	5137ms
Deduplication.No Duplicate Events In Batch	✅	31ms
Header Behavior On Retry.Attempt Header Starts At One	✅	7ms
Header Behavior On Retry.Attempt Header Increments On Retry	✅	10134ms
Header Behavior On Retry.Request Id Preserved On Retry	✅	5136ms
Header Behavior On Retry.Different Requests Have Different Request Ids	✅	2014ms
Header Behavior On Retry.Request Timestamp Changes On Retry	✅	5137ms
Response Format Validation.Success Response Has Uuid Keyed Results	✅	7ms
Response Format Validation.Success Response Has Ok For Each Event	✅	28ms
Response Format Validation.Success No Retry After When All Ok	✅	28ms
Response Format Validation.Success Retry After Present When Retry Events	✅	130ms
Response Format Validation.Success No Retry After When Drop Only	✅	28ms
Response Format Validation.Response Echoes Request Id	✅	7ms
Retry Behavior.Retries On 408	✅	5132ms
Retry Behavior.Retries On 500	✅	5133ms
Retry Behavior.Retries On 503	✅	5137ms
Retry Behavior.Retries On 504	✅	5134ms
Retry Behavior.Retryable Errors Have Retry After	✅	2133ms
Retry Behavior.Respects Retry After On Retryable Error	✅	8140ms
Retry Behavior.Does Not Retry On 400	✅	2133ms
Retry Behavior.Does Not Retry On 401	✅	2133ms
Retry Behavior.Does Not Retry On 402	✅	2133ms
Retry Behavior.Does Not Retry On 413	✅	2133ms
Retry Behavior.Does Not Retry On 415	✅	2133ms
Retry Behavior.Non Retryable Errors Have No Retry After	✅	2134ms
Retry Behavior.Implements Backoff	✅	15146ms
Retry Behavior.Max Retries Respected	✅	15143ms
Partial Batch Handling.Handles 200 Full Success	✅	2009ms
Partial Batch Handling.Handles 200 With All Ok	✅	3033ms
Partial Batch Handling.Does Not Retry Dropped Events	✅	3031ms
Partial Batch Handling.Does Not Retry Limited Events	✅	3032ms
Partial Batch Handling.Prunes Ok Events On Partial Retry	✅	5136ms
Partial Batch Handling.Prunes Dropped Events On Partial Retry	✅	5133ms
Partial Batch Handling.Retries Only Retry Events From Partial	✅	5139ms
Partial Batch Handling.Partial Retry Preserves Uuids	✅	5133ms
Partial Batch Handling.Partial Retry Attempt Header Increments	✅	5136ms
Partial Batch Handling.Partial Retry Request Id Preserved	✅	5136ms
Partial Batch Handling.Respects Retry After On Partial	✅	5136ms
Partial Batch Handling.Unknown Result Treated As Terminal	✅	3030ms
Partial Batch Handling.Mixed Ok Drop Limited No Retry	✅	3034ms
Compression.Sends Gzip Content Encoding	✅	16ms
Compression.No Content Encoding When Disabled	✅	7ms
Compression.Compressed Body Is Decompressible	✅	6ms
Error Handling.Does Not Retry On Unknown 4Xx	✅	2132ms
Event Options.Cookieless Mode Override	✅	7ms
Event Options.Disable Skew Correction Override	✅	6ms
Event Options.Process Person Profile Override	✅	6ms
Event Options.Product Tour Id Override	✅	6ms
Event Options.Unset Options Omitted	✅	6ms
Event Options.Options Override In Batch	✅	9ms
Geoip And Historical Migration.Geoip Disable Injected Into Properties	✅	5ms
Geoip And Historical Migration.Historical Migration Set In Body	✅	6ms
Geoip And Historical Migration.Historical Migration Absent By Default	✅	6ms

Feature_Flags Tests

✅ 17/17 tests passed

View Details

Test	Status	Duration
Request Payload.Request With Person Properties Device Id	✅	16ms
Request Payload.Flags Request Uses V2 Query Param	✅	16ms
Request Payload.Flags Request Hits Flags Path Not Decide	✅	16ms
Request Payload.Flags Request Omits Authorization Header	✅	15ms
Request Payload.Token In Flags Body Matches Init	✅	16ms
Request Payload.Groups Round Trip	✅	16ms
Request Payload.Groups Default To Empty Object	✅	16ms
Request Payload.Disable Geoip False Propagates As Geoip Disable False	✅	16ms
Request Payload.Disable Geoip Omitted Defaults To False	✅	16ms
Request Payload.Flag Keys To Evaluate Contains Only Requested Key	✅	16ms
Request Lifecycle.No Flags Request On Init Alone	✅	2ms
Request Lifecycle.No Flags Request On Normal Capture	✅	6ms
Request Lifecycle.Two Flag Calls Produce Two Remote Requests	✅	29ms
Request Lifecycle.Mock Response Value Is Returned To Caller	✅	17ms
Retry Behavior.Retries Flags On 502	✅	17ms
Retry Behavior.Retries Flags On 504	✅	17ms
Side Effect Events.Get Feature Flag Captures Feature Flag Called Event	✅	17ms

[greptile-apps]

_{Reviews (1): Last reviewed commit: "fix(flags): align presence operator sema..." | Re-trigger Greptile}