Replace a StopIteration exception with for-else

[noklam]

NOTE: Kedro datasets are moving from kedro.extras.datasets to a separate kedro-datasets package in
kedro-plugins repository. Any changes to the dataset implementations
should be done by opening a pull request in that repository.

Description

I have read the logic how Kedro import datasets many time, I finally realise this can be simplified with for-else. It also reveals a hidden bug.

kedro/kedro/io/core.py

Lines 380 to 396 in 38dfe6f

	class_obj = config.pop("type")
	if isinstance(class_obj, str):
	if len(class_obj.strip(".")) != len(class_obj):
	raise DataSetError(
	"'type' class path does not support relative "
	"paths or paths ending with a dot."
	)
	class_paths = (prefix + class_obj for prefix in _DEFAULT_PACKAGES)
	trials = (_load_obj(class_path) for class_path in class_paths)
	try:
	class_obj = next(obj for obj in trials if obj is not None)
	except StopIteration as exc:
	raise DataSetError(
	f"Class '{class_obj}' not found or one of its dependencies "
	f"has not been installed."
	) from exc

class_obj can be None, adding str to None result in type error but this is hidden by the load_obj

prefix + class_obj

This is only a few lines of change but take me a while to figure it out, the error was complicated due to many layers of try-except. this will help us to fix #2943 and improve kedro.io.core

Development notes

I refactor some logic in a separate PR, the class_obj was overused and make it very hard to debug.

Developer Certificate of Origin

We need all contributions to comply with the Developer Certificate of Origin (DCO). All commits must be signed off by including a Signed-off-by line in the commit message. See our wiki for guidance.

If your PR is blocked due to unsigned commits, then you must follow the instructions under "Rebase the branch" on the GitHub Checks page for your PR. This will retroactively add the sign-off to all unsigned commits and allow the DCO check to pass.

Checklist

• Read the contributing guidelines
• Signed off each commit with a Developer Certificate of Origin (DCO)
• Opened this PR as a 'Draft Pull Request' if it is work-in-progress
• Updated the documentation to reflect the code changes
• Added a description of this change in the RELEASE.md file
• Added tests to cover my changes
• Checked if this change will affect Kedro-Viz, and if so, communicated that with the Viz team

[idanov]

Loving it ❤️

[astrojuanlu]

No comment on the implementation (deferring to other engineers), just wanted to remind that this is not a fix to #2943. Just tested it and the error messages are the same and the import errors still get shadowed.

[merelcht]

No comment on the implementation (deferring to other engineers), just wanted to remind that this is not a fix to #2943. Just tested it and the error messages are the same and the import errors still get shadowed.

@astrojuanlu It says in the PR description "this will help us to fix #2943 and improve kedro.io.core" so it's not meant as a complete fix.

[astrojuanlu]

I know, but GitHub will automatically close it, so I wrote the comment for future reference 😅

[datajoely]

so elegant and now I actually have an example when this comes up!

[merelcht]

I can imagine this took a while to figure out! Nice improvement ⭐