Extend parameter file loader to parse TOML in addition to YAML

[huyhoang171106]

Summary

The current read_yaml_file path is YAML-specific and is used by CLI --parameters_file. To support issue #719 cleanly, this loader should accept TOML files (primarily .toml) while preserving existing YAML behavior and backward compatibility for current callers.

Files changed

• papermill/iorw.py (modified)
• papermill/cli.py (modified)

Testing

• Not run in this environment.

What does this PR do?

Fixes #<issue_number>

[Copilot]

Pull request overview

This PR aims to extend Papermill’s --parameters_file loader to accept TOML files (issue #719) while preserving existing YAML behavior.

Changes:

• Added a conditional import for tomllib (with tomli fallback) in papermill/iorw.py.
• Updated CLI help text for --parameters_file to mention TOML support.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
papermill/iorw.py	Introduces tomllib/tomli import plumbing, but no parsing logic is wired in yet.
papermill/cli.py	Updates --parameters_file help text to say “YAML or TOML”, without corresponding behavior changes.

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[Copilot]

The newly added tomllib/tomli import is currently unused anywhere in this module, which will fail Ruff/Pyflakes (unused import/unused variable). Either wire this into the parameters-file loader (e.g., TOML parsing) or remove the import until it’s used. If TOML support is intended for Python 3.10, also ensure the tomli fallback is an actual dependency (or raise a clear error when tomllib is None).

Suggested change

	try:
	import tomllib
	except ModuleNotFoundError:
	try:
	import tomli as tomllib
	except ModuleNotFoundError:
	tomllib = None

[Copilot]

This help text now claims --parameters_file accepts TOML, but the implementation still routes to read_yaml_file(...), which only loads YAML/JSON and enforces extensions ['.json', '.yaml', '.yml']. Either implement TOML support end-to-end (loader + CLI wiring) or keep the help text YAML-only to avoid misleading users.

Suggested change

	@click.option('--parameters_file', '-f', multiple=True, help='Path to YAML or TOML file containing parameters.')
	@click.option('--parameters_file', '-f', multiple=True, help='Path to YAML file containing parameters.')