Add json.marshal and json.unmarshal cel functions by NicholasBlaskey · Pull Request #1033 · kubernetes-sigs/kro

NicholasBlaskey · 2026-02-10T18:23:14Z

Add a json cel library to allow easier integration from / to json in RGDs

initially has

json.marshal
json.unmarshal

Tested with example.

Also tested error case of

                    - name: JSON_UNMARSHAL_ERROR_EXAMPLE
                      value: "${json.unmarshal('{\"exampleJSONKey\": \"exampleJSONValue\"}').exampleJSONKey}"

which causes a reconciliation failure

    Last Transition Time:  2026-02-10T19:45:47Z
    Message:               resource reconciliation failed: node "deployment": eval "json.unmarshal('not valid json at all').key": json.unmarshal failed to parse JSON: invalid character 'o' in literal null (expecting 'u')
    Observed Generation:   1
    Reason:                NotReady
    Status:                False
    Type:                  Ready

linux-foundation-easycla · 2026-02-10T18:23:23Z

The committers listed above are authorized under a signed CLA.

✅ login: NicholasBlaskey / name: Nick Blaskey (91eebbe, bb560d3)

k8s-ci-robot · 2026-02-10T18:23:24Z

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k8s-ci-robot · 2026-02-10T18:23:25Z

Hi @NicholasBlaskey. Thanks for your PR.

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a-hilaly · 2026-02-11T01:40:48Z

/ok-to-test

a-hilaly

Thank you Nick - i left one nit comment below

a-hilaly · 2026-02-11T05:17:21Z

I agree that the cel package deserves a better organization. Can we make this change in a seperate PR?

yes please, this should be focused to the functions only.

Yep can do

I moved these functions into a new package to resolve a circular import error I was getting

created #1043

a-hilaly · 2026-02-11T05:17:57Z

/retest

a-hilaly

Can you please update the CEL library docs? https://kro.run/docs/concepts/rgd/cel-expressions#available-cel-libraries

NicholasBlaskey · 2026-02-12T01:10:07Z

Can you please update the CEL library docs? https://kro.run/docs/concepts/rgd/cel-expressions#available-cel-libraries

updated

a-hilaly

Thank you @NicholasBlaskey !
/approve

a-hilaly · 2026-02-12T01:14:58Z

@jakobmoellerdev @matthchr shall we pin this for 0.9.0? or are we good with a 0.8.6? personally i'm fine with either

jakobmoellerdev · 2026-02-11T09:08:21Z

yes please, this should be focused to the functions only.

jakobmoellerdev · 2026-02-11T09:08:58Z

+
+func (l *jsonLibrary) CompileOptions() []cel.EnvOption {
+	return []cel.EnvOption{
+		cel.Function("json.unmarshal",


this should be versioned internally to v1alpha1

Could you clarify what you mean for versioned internally here?

I see some other libraries have integer versioning like this but not seeing any use a string version like v1alpha1. The random library also doesn't seem to have any versioning currently.
https://github.com/google/cel-go/blob/v0.27.0/ext/lists.go#L213

mabye take a look at https://github.com/google/cel-go/blob/v0.27.0/ext/lists.go#L175-L189 or https://github.com/google/cel-go/blob/v0.27.0/ext/sets.go#L88-L97. Its basically about introducing a version so we can control it later. i dont really mind if its v1alpha1 or an integer tbh.

added support for setting a version

currently the version integer is unused but can be referenced for future updates to the library

jakobmoellerdev · 2026-02-11T09:09:47Z

+}
+
+func unmarshalJSON(jsonString ref.Val) ref.Val {
+	if jsonString.Type() != types.StringType {


I think you could use the native default type adapter here to get a string.

jakobmoellerdev · 2026-02-12T07:25:35Z

I would favor a pin but won't block on 0.8.6

jakobmoellerdev

/lgtm
/hold

holding until 0.9.0 or if we have another approve ack this for next patch

jakobmoellerdev · 2026-02-13T07:17:41Z

On another note: https://github.com/google/cel-go/pull/1261/changes introduced a JSON Value compatibility. Do you think this is relevant here?

NicholasBlaskey · 2026-02-13T18:01:56Z

On another note: https://github.com/google/cel-go/pull/1261/changes introduced a JSON Value compatibility. Do you think this is relevant here?

doesn't seem relevant for unmarshal

For marshalJSON we could use value.ConvertToNative(types.JSONValueType) instead of our helper conversion.GoNativeType(value).

As far as I can tell they should be equivalent but don't have a strong opinion either way, open to changing it after #1047 merges

a-hilaly

👍

a-hilaly · 2026-02-25T03:51:54Z

@NicholasBlaskey can you please rebase this one?

k8s-ci-robot · 2026-02-25T23:35:39Z

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: a-hilaly, NicholasBlaskey

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a-hilaly · 2026-02-25T23:35:50Z

cc @jakobmoellerdev

a-hilaly · 2026-02-25T23:44:57Z

/unhold

jakobmoellerdev

/lgtm

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k8s-ci-robot requested review from barney-s and jakobmoellerdev February 10, 2026 18:23

NicholasBlaskey force-pushed the json_lib branch from c64d39a to f20a252 Compare February 10, 2026 20:46

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NicholasBlaskey added 2 commits February 25, 2026 22:35

Add json.marshal and json.unmarshal CEL functions

bb560d3

Add version support for the cel json library

91eebbe

NicholasBlaskey force-pushed the json_lib branch from cde882c to 91eebbe Compare February 25, 2026 23:10

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k8s-ci-robot merged commit f8f5946 into kubernetes-sigs:main Feb 26, 2026
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