Fix Redis key generation to be stable across working directories

[mateo-berri]

Relevant issues

Pre-Submission checklist

• I have added testing in the tests directory
• My PR's scope is isolated - fixes Redis key stability issue
• Added comprehensive test case for the fix

Type

🐛 Bug Fix
✅ Test

Changes

Problem

The redis_key_for() function was generating different Redis keys for the same cassette file depending on the current working directory. This caused cache misses and inconsistent behavior when tests were run from different directories.

Solution

Modified redis_key_for() in tests/_vcr_redis_persister.py to:

1. Convert the cassette path to an absolute path first
2. Calculate the relative path from the repository root (stored in _REPO_ROOT) instead of the current working directory
3. Handle edge cases where the path is outside the repo root by falling back to the basename

Testing

Added test_redis_key_is_stable_across_working_directories() in tests/llm_translation/test_vcr_redis_persister.py that:

• Verifies the Redis key is identical when generated from the repo root, a subdirectory, and a temporary directory
• Confirms the key format matches the expected pattern: litellm:vcr:cassette:tests/llm_translation/test_anthropic/test_streaming

This ensures VCR cassette caching works reliably regardless of where tests are executed from.

Slack Thread

  

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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[greptile-apps]

Greptile Summary

This PR fixes redis_key_for() in tests/_vcr_redis_persister.py to produce a stable Redis key regardless of the current working directory by resolving all cassette paths to absolute and then relativizing against a module-level _REPO_ROOT constant computed from __file__. The accompanying test exercises three distinct working directories to confirm key stability.

Confidence Score: 4/5

Safe to merge; fix is correct for all practical cases and only has minor hardening gaps.

The fix is logically sound and well-tested. The only findings are P2: a basename-based fallback that could theoretically collide on Windows cross-drive scenarios, and use of abspath rather than realpath which could misfire when symlinks are involved. Neither affects the primary Linux/macOS CI path.

tests/_vcr_redis_persister.py — the fallback and symlink handling in redis_key_for.

Important Files Changed

Filename	Overview
tests/_vcr_redis_persister.py	Adds _REPO_ROOT constant computed from __file__ at import time; redis_key_for() now resolves paths to absolute first, then relativizes against _REPO_ROOT, with a ValueError fallback to basename for cross-drive Windows paths.
tests/llm_translation/test_vcr_redis_persister.py	Adds test_redis_key_is_stable_across_working_directories which verifies key stability across three different working directories using monkeypatch.chdir; no network calls, correctly uses fakeredis for all other tests.

_{Reviews (1): Last reviewed commit: "fix(tests): anchor VCR redis cassette ke..." | Re-trigger Greptile}

[greptile-apps]

os.path.abspath does not resolve symlinks, so _REPO_ROOT and a cassette path can represent the same physical location via different string prefixes (one through a symlink, one through the real path). In that case os.path.relpath(abs_path, start=_REPO_ROOT) produces a ../../… path which the subsequent lstrip("./") then silently mangles into a wrong key. Using os.path.realpath for both would make the prefix comparison reliable.

Suggested change

	_REPO_ROOT = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
	_REPO_ROOT = os.path.dirname(os.path.dirname(os.path.realpath(__file__)))

[greptile-apps]

Consistent with using realpath for _REPO_ROOT, abs_path should also be resolved through any symlinks before computing the relative path, otherwise the prefix comparison can still fail when the cassette path arrives via a symlinked directory.

Suggested change

	abs_path = os.path.abspath(str(cassette_path))
	abs_path = os.path.realpath(str(cassette_path))

[greptile-apps]

The ValueError fallback (Windows cross-drive paths) uses only os.path.basename, which drops all directory context. Two cassettes in different subdirectories that share the same filename — e.g. tests/a/test_foo.yaml and tests/b/test_foo.yaml — would both resolve to litellm:vcr:cassette:test_foo and silently share the same Redis entry. Using a short hash of the full absolute path as the fallback would avoid this collision while remaining stable.

Suggested change

	except ValueError:
	rel = os.path.basename(abs_path)
	except ValueError:
	import hashlib
	rel = hashlib.sha1(abs_path.encode()).hexdigest()[:16]