fix: Preserve exception stack frame paths

[marandaneto]

💡 Motivation and Context

Fixes #212.

Captured exception stack frames currently set filename to File.basename(abs_path), which drops project-relative directories such as app/services/foo/bar.rb. PostHog Error Tracking renders filename, so frames with the same basename become hard to distinguish.

This change preserves useful relative paths for stack frame filenames while keeping abs_path unchanged. The changeset covers both posthog-ruby and posthog-rails because Rails users are affected by the captured exception payload.

💚 How did you test it?

• bundle exec rspec spec/posthog/exception_capture_spec.rb
• bundle exec rspec
• bundle exec rubocop

📝 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 implemented this change in a dedicated git worktree. The implementation follows the issue recommendation by computing stack frame filenames from known roots: Rails.root or the current working directory for in-app frames, and the longest matching $LOAD_PATH entry for gem frames. The fallback keeps the original path rather than collapsing to a basename, so directory context is preserved.

Follow-up review feedback replaced the trailing slash regex with a linear implementation, evaluated Rails.root only once, and added the Rails changeset entry.

[github-actions]

posthog-ruby Compliance Report

Date: 2026-07-03 09:39:13 UTC
Duration: 98227ms

✅ 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	✅	107ms
Format Validation.Event Has Lib Properties	✅	109ms
Format Validation.Distinct Id Is String	✅	107ms
Format Validation.Token Is Present	✅	107ms
Format Validation.Custom Properties Preserved	✅	106ms
Format Validation.Event Has Timestamp	✅	107ms
Retry Behavior.Retries On 503	✅	5312ms
Retry Behavior.Does Not Retry On 400	✅	2111ms
Retry Behavior.Does Not Retry On 401	✅	2109ms
Retry Behavior.Respects Retry After Header	✅	8118ms
Retry Behavior.Implements Backoff	✅	15623ms
Retry Behavior.Retries On 500	✅	5212ms
Retry Behavior.Retries On 502	✅	5212ms
Retry Behavior.Retries On 504	✅	5212ms
Retry Behavior.Max Retries Respected	✅	15514ms
Deduplication.Generates Unique Uuids	✅	113ms
Deduplication.Preserves Uuid On Retry	✅	5212ms
Deduplication.Preserves Uuid And Timestamp On Retry	✅	10310ms
Deduplication.Preserves Uuid And Timestamp On Batch Retry	✅	5215ms
Deduplication.No Duplicate Events In Batch	✅	112ms
Deduplication.Different Events Have Different Uuids	✅	109ms
Compression.Sends Gzip When Enabled	✅	107ms
Batch Format.Uses Proper Batch Structure	✅	108ms
Batch Format.Flush With No Events Sends Nothing	✅	5ms
Batch Format.Multiple Events Batched Together	✅	109ms
Error Handling.Does Not Retry On 403	✅	2109ms
Error Handling.Does Not Retry On 413	✅	2109ms
Error Handling.Retries On 408	✅	5212ms

Feature_Flags Tests

✅ 17/17 tests passed

View Details

Test	Status	Duration
Request Payload.Request With Person Properties Device Id	✅	109ms
Request Payload.Flags Request Uses V2 Query Param	✅	107ms
Request Payload.Flags Request Hits Flags Path Not Decide	✅	108ms
Request Payload.Flags Request Omits Authorization Header	✅	108ms
Request Payload.Token In Flags Body Matches Init	✅	108ms
Request Payload.Groups Round Trip	✅	109ms
Request Payload.Groups Default To Empty Object	✅	108ms
Request Payload.Disable Geoip False Propagates As Geoip Disable False	✅	108ms
Request Payload.Disable Geoip Omitted Defaults To False	✅	108ms
Request Payload.Flag Keys To Evaluate Contains Only Requested Key	✅	107ms
Request Lifecycle.No Flags Request On Init Alone	✅	3ms
Request Lifecycle.No Flags Request On Normal Capture	✅	106ms
Request Lifecycle.Two Flag Calls Produce Two Remote Requests	✅	112ms
Request Lifecycle.Mock Response Value Is Returned To Caller	✅	106ms
Retry Behavior.Retries Flags On 502	✅	239ms
Retry Behavior.Retries Flags On 504	✅	211ms
Side Effect Events.Get Feature Flag Captures Feature Flag Called Event	✅	109ms

[greptile-apps]

_{Reviews (1): Last reviewed commit: "fix: Preserve relative exception filenam..." | Re-trigger Greptile}

[marandaneto]

@PostHog/team-error-tracking not sure if thats what we want, but opened a pr with a possible fix, lemme know

[hpouillot]

Yes, it should be fixed with this PR: #214

[marandaneto]

closing in favor of #214