feat: add semver targeting support to local flag evaluation

[dmarticus]

Summary

• Add 9 semver comparison operators (semver_eq, semver_neq, semver_gt, semver_gte, semver_lt, semver_lte, semver_tilde, semver_caret, semver_wildcard) for local feature flag evaluation
• Implements the client-side evaluation to match feat(flags): support semver comparisons in user_blast_radius posthog#44596
• Parsing handles v-prefix, whitespace, pre-release suffixes, leading zeros, and 4-part versions

Why not use a semver library?

Libraries like packaging and semver exist but aren't runtime dependencies of this SDK. The current runtime deps are intentionally minimal (requests, six, python-dateutil, backoff, distro, typing-extensions), and adding a dependency for ~20 lines of string splitting isn't worth the install footprint cost for SDK consumers. The Rust feature-flags service uses its ecosystem's semver crate, but Rust deps don't have the same user-facing cost as Python deps.

Test plan

• All 9 operators tested with positive/negative cases
• Edge cases: v-prefix, whitespace, leading zeros, pre-release suffixes, partial versions, 4-part versions
• Caret operator ^0.x.y behavior per semver spec
• Invalid input and missing property handling
• All 115 tests pass (12 new + 103 existing)

[github-actions]

posthog-python Compliance Report

Date: 2026-02-27 01:55:47 UTC
Duration: 159371ms

✅ All Tests Passed!

29/29 tests passed

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Capture Tests

✅ 29/29 tests passed

View Details

Test	Status	Duration
Format Validation.Event Has Required Fields	✅	516ms
Format Validation.Event Has Uuid	✅	1507ms
Format Validation.Event Has Lib Properties	✅	1507ms
Format Validation.Distinct Id Is String	✅	1507ms
Format Validation.Token Is Present	✅	1507ms
Format Validation.Custom Properties Preserved	✅	1507ms
Format Validation.Event Has Timestamp	✅	1507ms
Retry Behavior.Retries On 503	✅	9514ms
Retry Behavior.Does Not Retry On 400	✅	3511ms
Retry Behavior.Does Not Retry On 401	✅	3507ms
Retry Behavior.Respects Retry After Header	✅	9510ms
Retry Behavior.Implements Backoff	✅	23532ms
Retry Behavior.Retries On 500	✅	7502ms
Retry Behavior.Retries On 502	✅	7513ms
Retry Behavior.Retries On 504	✅	7516ms
Retry Behavior.Max Retries Respected	✅	23528ms
Deduplication.Generates Unique Uuids	✅	1498ms
Deduplication.Preserves Uuid On Retry	✅	7511ms
Deduplication.Preserves Uuid And Timestamp On Retry	✅	14525ms
Deduplication.Preserves Uuid And Timestamp On Batch Retry	✅	7505ms
Deduplication.No Duplicate Events In Batch	✅	1506ms
Deduplication.Different Events Have Different Uuids	✅	1507ms
Compression.Sends Gzip When Enabled	✅	1507ms
Batch Format.Uses Proper Batch Structure	✅	1507ms
Batch Format.Flush With No Events Sends Nothing	✅	1004ms
Batch Format.Multiple Events Batched Together	✅	1506ms
Error Handling.Does Not Retry On 403	✅	3508ms
Error Handling.Does Not Retry On 413	✅	3508ms
Error Handling.Retries On 408	✅	7512ms

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