File extensions comparisons are case sensitive

[dholbach]

From Ada Logics

In the lines

kustomize-controller/controllers/kustomization_generator.go

Lines 164 to 167 in 1e01d80

	extension := filepath.Ext(path)
	if extension != ".yaml" && extension != ".yml" {
	return nil
	}

A check happens on the file extension for YAML files

However, the check is case sensitive. We recommend either documenting this or allowing file extensions that are not purely limited to lowercase extensions.

Recommendation
Normalise file extensions when processing them to allow uppercase letters in extensions or clarify that files must be lowercase.

[relu]

Looking at the kustomize source code, it seems the list of recognized files only accounts for the lowercase variant.
I wasn't able to find any user-oriented documentation regarding this convention.

Given there's no support upstream for upper or mixed-case variants of the file extension I think it's safe to close this as "won't fix".