OmegaConfigLoader should not throw MissingConfigException when the file is empty

[noklam]

Description

Related #2556

Currently, if you have an empty configuration file with OmegaConfigLoader, you will get this error which isn't very accurate.

This draft PR is just a starting point, it's expected to be picked up by someone and worked on it further.

kedro/kedro/config/omegaconf_config.py

Lines 195 to 200 in 6531457

	if not config:
	raise MissingConfigException(
	f"No files of YAML or JSON format found in {base_path} or {env_path} matching"
	f" the glob pattern(s): {[*self.config_patterns[key]]}"
	)
	return config

This is due to the fact that we always return an empty dictionary when we load the configuration. In other words, we cannot distinguish between an empty file and a missing file.

kedro/kedro/config/omegaconf_config.py

Lines 274 to 275 in 6531457

	if not aggregate_config:
	return {}

We should take this as an opportunity to refactor and simplify these conditions. Bottom line we should have a better error message to handle empty configuration properly.

Context

How has this bug affected you? What were you trying to accomplish?
I was confused with the error because I have the config file. Initially I thought my configuration is not in the right place or I didn't config the config_patterns properly. The config file is actually read but the error is confusing.

Expected Result

Tell us what should happen.
It should return an empty dictionary {} instead of getting error.

Actual Result

Tell us what happens instead.
MissingConfigException is thrown.

-- If you received an error, place it here.

-- Separate them if you have more than one.