feat: support inline configurations

[TLDMain]

Relevant issue #1966

[linux-foundation-easycla]

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[stormqueen1990]

Hi there, @TLDMain!

Thanks for your contribution!

This PR is referring to an old issue that was closed before it was triaged. Could you please elaborate on what is the use case you're trying to address here?

/hold

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/lifecycle stale

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[TLDMain]

Hi there, @stormqueen1990!

Thanks for your feedback!

This PR addresses the need to streamline kustomize configurations by allowing inlined configurations directly within the kustomization.yaml file, similar to how patches are currently handled. The use case here is to simplify the sharing and management of kustomize configurations by embedding them within a single file, eliminating the need for separate configuration files. This makes it easier to provide comprehensive and portable examples.

For instance, with this change, configurations can be inlined as follows:

apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization
resources:
  - helmrelease.yaml
configMapGenerator:
  - name: helmrelease-values
    files:
      - values.yaml=helmrelease.values.yaml
configurations:
  - |
    nameReference:
      - kind: ConfigMap
        version: v1
        fieldSpecs:
          - path: spec/valuesFrom/name
            kind: HelmRelease

This enhancement allows users to consolidate their configurations, making it more convenient to manage and share kustomize setups.

/remove-lifecycle stale
/label tide/merge-method-squash

[stormqueen1990]

/triage under-consideration

[varshaprasad96]

This looks good to me! Thank you!
/lgtm

I'll wait for approval, still some other maintainer can also take a look.
cc: @stormqueen1990 @antoooks

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[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: stormqueen1990, TLDMain
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[stormqueen1990]

/remove-triage under-consideration
/ok-to-test
/unhold

[stormqueen1990]

Hi there, @TLDMain!

After reviewing this change, I noticed that the configurations field was meant to explicitly only accept paths to transformer configuration files:

kustomize/api/types/kustomization.go

Lines 168 to 169 in 77354d7

	// Configurations is a list of transformer configuration files
	Configurations []string `json:"configurations,omitempty" yaml:"configurations,omitempty"`

Accepting paths and inline configurations in the same configuration list without separate fields for each is inconsistent with how other configurations in the Kustomization API work right now -- for instance, patches have separate fields for a file path (path) and an inline patch (patch):

kustomize/api/types/patch.go

Lines 12 to 24 in f96ac2d

	type Patch struct {
	// Path is a relative file path to the patch file.
	Path string `json:"path,omitempty" yaml:"path,omitempty"`
	// Patch is the content of a patch.
	Patch string `json:"patch,omitempty" yaml:"patch,omitempty"`
	// Target points to the resources that the patch is applied to
	Target *Selector `json:"target,omitempty" yaml:"target,omitempty"`
	// Options is a list of options for the patch
	Options map[string]bool `json:"options,omitempty" yaml:"options,omitempty"`
	}

Could you please add a new field in the Kustomization type for these inline patches?

I suggest inlineConfigurations as the name. The type can still be a string slice, just like the current configurations field.

Thanks in advance!

[koba1t]

Hi @stormqueen1990

I suggest inlineConfigurations as the name. The type can still be a string slice, just like the current configurations field.

type Kustomization struct is our most important top-level configuration.
I feel we need to write The Enhancement Proposal and discuss the interface If we try to introduce any changes to that structure.
https://github.com/kubernetes-sigs/kustomize/blob/master/proposals/README.md

[TLDMain]

Hi there, @stormqueen1990!

Apologies for the incorrect analogy. I based these changes on the behavior of the transformers and generators fields, not on patches. Here's a similar PR: #3225. However, I can create a separate field if that's critical.

Also, the comments for these fields are similar to those in the configurations:

kustomize/api/types/kustomization.go

Lines 171 to 175 in 77354d7

	// Generators is a list of files containing custom generators
	Generators []string `json:"generators,omitempty" yaml:"generators,omitempty"`
	// Transformers is a list of files containing transformers
	Transformers []string `json:"transformers,omitempty" yaml:"transformers,omitempty"`

I'll wait for your decision.

[koba1t]

Hi @TLDMain

I think there is a many consideration point and need take a time that add new inlineConfigurations field for Kustomization struct.
I believe that is a better to use current Configurations []string field in this case and add carefully path check in code avoid some bugs.

Please add more strict check for string in Configurations field.

[TLDMain]

Hi @koba1t.

I suggest two options for checking: either use regex to verify that the string contains a file path, or check if the string contains multiple lines.

Alternatively, you can propose your own method for checking.

[koba1t]

@TLDMain
I am so sorry for the delayed response.

I have one suggestion.
If the contents of the field are a single line, the method is to go looking for the file to which it refers.

regexp would be difficult because different operating systems interpret them in different ways. Perhaps in the future there may be content that can be expressed on a single line, so it would be safer to check if it can be resolved with the file open function.

[k8s-ci-robot]

New changes are detected. LGTM label has been removed.

[TLDMain]

Hi. @koba1t.

Thank you for the suggestion!
I implemented the check for a newline in the configuration content, as you recommended.

However, this led to unexpected behavior: YAML files can be written in a single line, which caused issues with accurately interpreting the variable's content.
For example:

configurations:
  -  '{ images: [ { kind: MyKind, path: spec/container/image } ] }'

The previous approach, which attempted to parse YAML directly into a TransformerConfig structure, provided a better guarantee of correct content recognition.
I would revert to the previous behavior, as it covers more cases without errors.