fix(util): import MetaflowInternalError in read_artifacts_module

[Anai-Guo]

Problem

metaflow/util.py::read_artifacts_module raises MetaflowInternalError on both of its error paths, and documents it in the docstring:

Raises
-------
MetaflowInternalError
    If the file cannot be read or does not contain the ARTIFACTS variable.

but the name is never imported into metaflow/util.py. So neither raise can construct the exception — the name lookup fails first and the caller gets:

NameError: name 'MetaflowInternalError' is not defined

pyflakes metaflow/util.py flags exactly these two lines (621, 626) as undefined names.

The function is reachable from the CLI: metaflow/cli_components/step_cmd.py imports it and spin_step calls it whenever --artifacts-module is passed:

spin_artifacts = read_artifacts_module(artifacts_module) if artifacts_module else {}

so a mistyped path, or a module without an ARTIFACTS variable, produces a NameError instead of the intended error.

Fix

Add the deferred import, matching the existing idiom in this same file — compress_list (line 352) does exactly this, function-locally, because metaflow.util is imported early and a module-level from metaflow.exception import ... would risk a circular import:

def compress_list(lst, ...):
    from metaflow.exception import MetaflowInternalError

2 lines added, nothing else touched.

Verification

Real upstream metaflow/util.py and metaflow/exception.py, loaded under a metaflow package namespace with only metaflow._vendor.packaging.version (the single module-level metaflow import in util.py) and metaflow.extension_support (exception.py's extension hook, off the path under test) stubbed:

case	before	after
path that does not exist	NameError: name 'MetaflowInternalError' is not defined	MetaflowInternalError: Error reading file ...
module without ARTIFACTS	NameError: name 'MetaflowInternalError' is not defined	MetaflowInternalError: Error reading file ...
module with ARTIFACTS = {'a': 1}	{'a': 1}	{'a': 1} (unchanged)

pyflakes metaflow/util.py after the change: no undefined names.

Note (not changed here)

The explicit raise MetaflowInternalError("Module ... does not contain ARTIFACTS variable") inside the try is caught by the function's own broad except Exception as e and re-wrapped as "Error reading file ...", so that more specific message never reaches the user. That is pre-existing and independent of this fix; happy to add an except MetaflowInternalError: raise passthrough in a follow-up if you'd like it preserved.

🤖 Generated with Claude Code

[greptile-apps]

Greptile Summary

This PR fixes read_artifacts_module so its existing error paths can raise the documented MetaflowInternalError instead of failing with an undefined-name error.

• Adds the exception import locally to avoid the package's circular module dependency.
• Preserves successful artifact-module loading behavior.
• Allows CLI-level MetaflowException handling to process invalid artifact modules as intended.

Confidence Score: 5/5

The PR appears safe to merge and correctly restores the intended exception behavior.

The new function-local import follows established patterns in the same module, avoids introducing a module-level circular dependency, and makes both existing error paths raise the documented exception type.

Important Files Changed

Filename	Overview
metaflow/util.py	Adds the missing deferred import required by both existing MetaflowInternalError raise paths.

_{Reviews (1): Last reviewed commit: "fix(util): import MetaflowInternalError ..." | Re-trigger Greptile}