Python 3.14: UnboundLocalError in compute_metadata when repo_info is provided #8
Description
Bug Report
SDK version: braintrust 0.5.6
Python version: 3.14.2
Platform: macOS (darwin aarch64)
Description
When using braintrust.init() with repo_info and git_metadata_settings=GitMetadataSettings(collect="none"), the SDK crashes with UnboundLocalError: cannot access local variable 'merged_git_metadata_settings' during lazy experiment ID resolution.
This is a Python 3.14 scoping change as Python 3.14 enforces stricter scoping for variables defined only inside one branch of an if/else block.
Reproduction
import braintrust
from braintrust.git_fields import RepoInfo
braintrust.login(api_key="<key>", force_login=True)
repo_info = RepoInfo(commit="abc123", branch="main", dirty=False, author_name="test")
exp = braintrust.init(
project="my_project",
experiment="test_experiment",
repo_info=repo_info,
git_metadata_settings=braintrust.GitMetadataSettings(collect="none"),
)
exp.log(input={"test": "hello"}, output="world", scores={"accuracy": 1.0})
exp.flush() # Crashes hereError
File "braintrust/logger.py", line 1659, in compute_metadata
elif merged_git_metadata_settings and merged_git_metadata_settings.collect != "none":
^^^^^^^^^^^^^^^^^^^^^^^^^^^^
UnboundLocalError: cannot access local variable 'merged_git_metadata_settings' where it is not associated with a value
Root Cause
In logger.py around line 1642-1660, merged_git_metadata_settings is only assigned inside the else branch:
if repo_info: # line 1642
repo_info_arg = repo_info # line 1643 — skips assignment
else:
merged_git_metadata_settings = state.git_metadata_settings # line 1645 — only here
...
# Later:
elif merged_git_metadata_settings and ...: # line 1659 — BOOM: variable never assignedWhen repo_info is truthy (which it always is when you pass it), the else block never executes, so merged_git_metadata_settings is never assigned. Python 3.14 raises UnboundLocalError because the variable is referenced in a branch that's unreachable given the control flow.
Fix
Add merged_git_metadata_settings = None before the if/else block:
merged_git_metadata_settings = None # Ensure variable exists in all code paths
if repo_info:
repo_info_arg = repo_info
else:
merged_git_metadata_settings = state.git_metadata_settings
...Workaround
We patched the SDK source directly:
sed -i '' 's/ if repo_info:/ merged_git_metadata_settings = None\n if repo_info:/' .venv/lib/python3.14/site-packages/braintrust/logger.pyImpact
This blocks all experiment logging on Python 3.14. Project logging (traces) works fine — only experiments are affected because they use the lazy compute_metadata path.