GetFieldValue doesn't work with fields that contain dots(.)

[Goodwine]

Describe the bug

rnode.GetFieldValue doesn't work correctly when the target field contains a .

For example when I call rnode.GetFieldValue("foo.bar") this function will try to find field "bar" within field "foo" instead of finding the field "foo.bar"

Files that can reproduce the issue

package v1alpha1

import (
	"testing"

	"github.com/stretchr/testify/require"
	"sigs.k8s.io/kustomize/kyaml/kio"
	"sigs.k8s.io/kustomize/kyaml/yaml"
)

const input = `
kind: Pod
metadata:
  name: hello-world
  labels:
    app: hello-world-app
    foo.appname: hello-world-foo
`

func TestGetFieldValue(t *testing.T) {
	data, err := kio.ParseAll(input)
	require.NoError(t, err)

	labelRNode, err := data[0].Pipe(yaml.Lookup("metadata", "labels"))
	require.NoError(t, err)

	app, err := labelRNode.GetFieldValue("app")
	require.NoError(t, err)
	require.Equal(t, "hello-world-app", app)

	fooAppName, err := labelRNode.GetFieldValue("foo.appname")
	require.NoError(t, err)
	require.Equal(t, "hello-world-foo", fooAppName) // no field named 'foo.appname'
}

Expected output

labelRNode.GetFieldValue("foo.appname") should return hello-world-app

Actual output

labelRNode.GetFieldValue("foo.appname") returns an error because there is no field foo

Kustomize version

require sigs.k8s.io/kustomize/kyaml v0.13.1

Additional context

If my pod was defined as:

kind: Pod
metadata:
  name: hello-world
  labels:
    app: hello-world-app
    foo.appname: hello-world-foo
    foo:
      appname: wtf       # <--------

then it would have "worked" but it would have returned wtf instead of hello-world-app.

Workaround

I can still use rnode.Pipe(yaml.Lookup("foo.appname")) and I can also use m, err := rnode.Map() followed by m["foo.appname"], it just caught me offguard

[natasha41575]

/triage accepted

There are these path splitters in api that allow escaping delimiters, with a TODO to move them to kyaml. Part of this issue would to be to finally do that TODO, and use it in rnode.GetFieldValue, so that you can do something like rnode.GetFieldValue("foo\.bar").

Edit: Forgot to link the path splitters: https://github.com/kubernetes-sigs/kustomize/blob/master/api/internal/utils/pathsplitter.go#L8

[Goodwine]

Is there an example of something that was migrated over from strings.Split to the better path splitters in case this is something I could try to work on?

In hindsight I guess it makes sense obj.foo.bar doesn't work because in regular JSON I would do obj["foo.bar"], I guess what was surprising to me is that I expected GetFieldValue not to recursively go down the path, the name of the function made me think I was extracting the value of the key/field

[natasha41575]

It's used in the replacements filter here:

kustomize/api/filters/replacement/replacement.go

Line 116 in 6950a0d

fieldPath := utils.SmarterPathSplitter(fp, ".")

The purpose is to traverse a path that looks like metadata.annotations.config\.kubernetes\.io/local-config. This lets you target something like

metadata:
  annotations:
    config.kubernetes.io/local-config: # this is the target field here

[r0ushann]

hello! I'm interested in this issue. please guide me.

[NikhilSharmaWe]

@natasha41575 So I think there is no need to make any changes in the repo since it is not a bug, am I right ?
Could you please inform if we need some improvements, I will look forward to work on it.

[natasha41575]

See my comment above: #4487 (comment). This explains the work that needs to be done to resolve this issue.