Fix Bug: _get_or_create_exp creates nested relative directories for file: URI file lock

[2young-2simple-sometimes-naive]

File: qlib/workflow/expm.py, line 236

Severity: Medium — silently creates garbage directory trees under the working directory on every new
experiment.

Root Cause

When the MLflow tracking URI uses the file: scheme, e.g. file:/home/user/project/mlruns, urlparse
decomposes it as:

• scheme = "file"
• netloc = "" (empty, because there is no // authority component)
• path = "/home/user/project/mlruns"

The lock path at line 236 is constructed as:

Path(os.path.join(pr.netloc, pr.path.lstrip("/"), "filelock"))

pr.path.lstrip("/") strips all leading slashes from the absolute path, turning
/home/user/project/mlruns into home/user/project/mlruns. Then os.path.join("",
"home/user/project/mlruns", "filelock") produces a relative path: home/user/project/mlruns/filelock.

When FileLock acquires this lock, it creates all parent directories relative to the process's current working directory, producing a nested copy of the full absolute path rooted at CWD (e.g., ./home/user/project/mlruns/).

Fix

One line change at expm.py:236:

Before:
with FileLock(Path(os.path.join(pr.netloc, pr.path.lstrip("/"), "filelock"))): # pylint: disable=E0110

After:
with FileLock(Path(pr.path) / "filelock"):

Path(pr.path) / "filelock" preserves the original absolute path from the parsed URI. It works correctly for all file: URI forms:

• file:/absolute/path gives /absolute/path/filelock
• file:///absolute/path gives /absolute/path/filelock
• file:relative/path gives relative/path/filelock (unchanged — relative URIs already worked)

Reproduction

import qlib
from qlib.workflow import R

qlib.init(provider_uri="~/.qlib/qlib_data/cn_data", region="cn")

On first call with a new experiment name, this hits _get_or_create_exp

and creates the nested directory tree.

with R.start(experiment_name="test_experiment"):
pass

After running, check the working directory — you will find a nested path like
./home/user/project/mlruns/ mirroring the absolute path structure but rooted at CWD.