feat(feature-flags): support early_exit in local evaluation

[gustavohstrassburger]

💡 Motivation and Context

PostHog/posthog#57321 added an early exit option to feature flags: when enabled, condition evaluation stops and returns false as soon as a user matches a group's targeting but is excluded by its rollout percentage, instead of falling through to later groups. That was implemented server-side (Rust engine), and PostHog/posthog-js#3705 ported it to posthog-node's local evaluation.

posthog-python re-implements the same matching loop, so without honoring filters.early_exit its locally-evaluated flags could diverge from server-side results. This PR applies the same approach to posthog-python.

💚 How did you test it?

Added unit tests in test_feature_flags.py covering early-exit enabled (returns False without evaluating later groups), unset/explicitly-disabled (falls through to a later matching group), a rollout-only group with no property filters, and a property-mismatch case (does not early exit). The full feature-flag suites pass (test_feature_flags.py, test_feature_flag_result.py, test_client.py — 285 tests). Lint (ruff) is clean.

Changes

• Introduce a ConditionMatch tri-state (MATCH / NO_MATCH / OUT_OF_ROLLOUT_BOUND) returned by is_condition_match, so the evaluation loop can distinguish a rollout exclusion from a property mismatch.
• Honor filters.early_exit in match_feature_flag_properties: when enabled and a group's property filters match but rollout excludes the user (OUT_OF_ROLLOUT_BOUND), return False immediately rather than evaluating later groups. Property mismatches still fall through, mirroring the Rust semantics exactly.
• Both local-evaluation entry points (get_feature_flag and evaluate_flags) route through match_feature_flag_properties, so both honor the new behavior.

📝 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 sampo add to generate a changeset file

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Created with PostHog Code

[github-actions]

posthog-python Compliance Report

Date: 2026-06-04 18:29:13 UTC
Duration: 176159ms

✅ All Tests Passed!

45/45 tests passed

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Capture Tests

✅ 29/29 tests passed

View Details

Test	Status	Duration
Format Validation.Event Has Required Fields	✅	518ms
Format Validation.Event Has Uuid	✅	1507ms
Format Validation.Event Has Lib Properties	✅	1508ms
Format Validation.Distinct Id Is String	✅	1507ms
Format Validation.Token Is Present	✅	1507ms
Format Validation.Custom Properties Preserved	✅	1508ms
Format Validation.Event Has Timestamp	✅	1507ms
Retry Behavior.Retries On 503	✅	9517ms
Retry Behavior.Does Not Retry On 400	✅	3508ms
Retry Behavior.Does Not Retry On 401	✅	3509ms
Retry Behavior.Respects Retry After Header	✅	9514ms
Retry Behavior.Implements Backoff	✅	23519ms
Retry Behavior.Retries On 500	✅	7512ms
Retry Behavior.Retries On 502	✅	7517ms
Retry Behavior.Retries On 504	✅	7512ms
Retry Behavior.Max Retries Respected	✅	23531ms
Deduplication.Generates Unique Uuids	✅	1498ms
Deduplication.Preserves Uuid On Retry	✅	7511ms
Deduplication.Preserves Uuid And Timestamp On Retry	✅	14526ms
Deduplication.Preserves Uuid And Timestamp On Batch Retry	✅	7504ms
Deduplication.No Duplicate Events In Batch	✅	1508ms
Deduplication.Different Events Have Different Uuids	✅	1507ms
Compression.Sends Gzip When Enabled	✅	1508ms
Batch Format.Uses Proper Batch Structure	✅	1507ms
Batch Format.Flush With No Events Sends Nothing	✅	1005ms
Batch Format.Multiple Events Batched Together	✅	1505ms
Error Handling.Does Not Retry On 403	✅	3510ms
Error Handling.Does Not Retry On 413	✅	3506ms
Error Handling.Retries On 408	✅	7515ms

Feature_Flags Tests

✅ 16/16 tests passed

View Details

Test	Status	Duration
Request Payload.Request With Person Properties Device Id	✅	1003ms
Request Payload.Flags Request Uses V2 Query Param	✅	1007ms
Request Payload.Flags Request Hits Flags Path Not Decide	✅	1007ms
Request Payload.Flags Request Omits Authorization Header	✅	1007ms
Request Payload.Token In Flags Body Matches Init	✅	1007ms
Request Payload.Groups Round Trip	✅	1006ms
Request Payload.Groups Default To Empty Object	✅	1007ms
Request Payload.Person Properties Distinct Id Auto Populated When Caller Omits It	✅	1007ms
Request Payload.Disable Geoip False Propagates As Geoip Disable False	✅	1007ms
Request Payload.Disable Geoip Omitted Defaults To False	✅	1007ms
Request Payload.Flag Keys To Evaluate Contains Only Requested Key	✅	1006ms
Request Lifecycle.No Flags Request On Init Alone	✅	503ms
Request Lifecycle.No Flags Request On Normal Capture	✅	1507ms
Request Lifecycle.Two Flag Calls Produce Two Remote Requests	✅	1012ms
Request Lifecycle.Mock Response Value Is Returned To Caller	✅	1002ms
Side Effect Events.Get Feature Flag Captures Feature Flag Called Event	✅	1509ms

[greptile-apps]

Comments Outside Diff (1)

1. posthog/test/test_feature_flags.py, line 256-325 (link)

   Three non-parameterized tests covering related early-exit scenarios

   test_early_exit_on_rollout_only_group_with_no_property_filters, test_early_exit_does_not_trigger_on_property_mismatch, and test_early_exit_on_multivariate_flag each test a distinct scenario (no property filters, property mismatch, multivariate variant) but all follow the same two-group flag structure with early_exit: True. Per the repo's preference, these should be expressed as parameterized cases — either added to the existing @parameterized.expand block on test_early_exit (where the full flag fixture is passed as a parameter) or as a second parameterized test covering the alternative flag shapes.

   Context Used: Do not attempt to comment on incorrect alphabetica... (source)

   Prompt To Fix With AI

   This is a comment left during a code review.
   Path: posthog/test/test_feature_flags.py
   Line: 256-325
   
   Comment:
   **Three non-parameterized tests covering related early-exit scenarios**
   
   `test_early_exit_on_rollout_only_group_with_no_property_filters`, `test_early_exit_does_not_trigger_on_property_mismatch`, and `test_early_exit_on_multivariate_flag` each test a distinct scenario (no property filters, property mismatch, multivariate variant) but all follow the same two-group flag structure with `early_exit: True`. Per the repo's preference, these should be expressed as parameterized cases — either added to the existing `@parameterized.expand` block on `test_early_exit` (where the full flag fixture is passed as a parameter) or as a second parameterized test covering the alternative flag shapes.
   
   **Context Used:** Do not attempt to comment on incorrect alphabetica... ([source](https://app.greptile.com/review/custom-context?memory=instruction-0))
   
   How can I resolve this? If you propose a fix, please make it concise.

   Note: If this suggestion doesn't match your team's coding style, reply to this and let me know. I'll remember it for next time!

Prompt To Fix All With AI

Fix the following 1 code review issue. Work through them one at a time, proposing concise fixes.

---

### Issue 1 of 1
posthog/test/test_feature_flags.py:256-325
**Three non-parameterized tests covering related early-exit scenarios**

`test_early_exit_on_rollout_only_group_with_no_property_filters`, `test_early_exit_does_not_trigger_on_property_mismatch`, and `test_early_exit_on_multivariate_flag` each test a distinct scenario (no property filters, property mismatch, multivariate variant) but all follow the same two-group flag structure with `early_exit: True`. Per the repo's preference, these should be expressed as parameterized cases — either added to the existing `@parameterized.expand` block on `test_early_exit` (where the full flag fixture is passed as a parameter) or as a second parameterized test covering the alternative flag shapes.

_{Reviews (1): Last reviewed commit: "fix(feature-flags): remove redundant or ..." | Re-trigger Greptile}