[TEP-0145] CEL in WhenExpression #1074

Yongxuanzhang · 2023-09-28T15:40:32Z

This commit adds the proposal of adding CEL in WhenExpression

Signed-off-by: Yongxuan Zhang [email protected]

Yongxuanzhang · 2023-09-28T15:59:33Z

Hi @tektoncd/core-maintainers ptal at this proposal.
cc @vdemeester @pritidesai thought you might be interested

teps/0145-cel-in-whenexpression.md

JeromeJu · 2023-10-02T15:27:30Z

/assign

jerop · 2023-10-02T16:04:23Z

/kind tep

JeromeJu · 2023-10-02T16:15:36Z

/assign @pritidesai

JeromeJu · 2023-10-02T16:15:46Z

/assign @vdemeester

QuanZhang-William

Thanks @Yongxuanzhang, great TEP! I left some comments, but lgtm in general.

I believe having this feature and Param Enum can improve UX significantly.

teps/0145-cel-in-whenexpression.md

QuanZhang-William · 2023-10-02T22:04:15Z

teps/0145-cel-in-whenexpression.md

+
+The new fields will be gated by a new feature flag, `enable-cel-whenexpression`, which will defaults to `"false"` while the feature is in alpha.
+
+The validation webhook will validate either the current when `input`+`operator`+`values` or `cel` is used, users cannot use both at the same time for one `WhenExpression`.


I'm wondering if the validation webhook can validate if the given CEL expression is syntactically valid or not?

Oh this is a great suggestion! Thanks!

teps/0145-cel-in-whenexpression.md

Yongxuanzhang · 2023-10-12T19:57:53Z

teps/0145-cel-in-whenexpression.md

+    - cel: '$(params.branch)'.matches('release/.*')"
+```
+
+### Variables Substitution


Hi @vdemeester, I added one more section since last time you reviewed. This section will discuss how we handle variable substitution in CEL expression and how we can prevent the attack. PTAL 🙏

Yongxuanzhang · 2023-10-12T19:58:26Z

Hi @pritidesai, @JeromeJu could you review this TEP? Thanks!

teps/0145-cel-in-whenexpression.md

pritidesai · 2023-10-13T00:20:58Z

teps/0145-cel-in-whenexpression.md

+    - input: "$(params.param1)$(params.param2)"
+      operator: notin
+      values: [""]
+```


Right, this is a workaround but @durera was hopping to implement more complex logic but chose to go this route since their desired conditional logic is not supported.

The desired conditional logic is:

whenAny: - input: "$(params.param1)" operator: notin values: [""] - input: "$(params.param2)" operator: in values: ["8.5", "8.6"]

which I think can supported with a single CEL expression:

when: cel: "'$(params.param1)' != '' || '$(params.param2)' == '8.5' || $(params.param2)' == '8.6'"

Do we know if there is any limitation on the length of the cel expression? If so, its worth documenting here.

Thanks! I missed the original one the user wants to use. Updated.

For the length limitation, I have searched a bit but could not find answers...

teps/0145-cel-in-whenexpression.md

pritidesai · 2023-10-13T00:31:09Z

teps/0145-cel-in-whenexpression.md

+
+### Variables Substitution
+
+The CEL in When Expressions should support current Tekton’s Params and Results [string substitutions](https://github.com/tektoncd/pipeline/blob/main/docs/variables.md#variables-available-in-a-pipeline). Array and object substitutions are not supported because Tekton doesn’t support whole array/object replacements in a string.


is this true? values is an array and it does honor the star notation, isn't it?

Its reasonable to implement only string params with CEL but are we supporting indexing into an array or referencing an object param using a key in CEL expressions?

Yes, I should clarify that we cannot reference to a whole array or object.

I remember there is an issue that we cannot reference param in "script", the case where a long string contains param reference.

I will remove this statement, and rephrase that we will support string replacements first

Removed this statement

teps/0145-cel-in-whenexpression.md

pritidesai · 2023-10-13T00:50:52Z

Thanks a bunch @Yongxuanzhang for all the efforts on this. This will be greatly appreciated and utilized by the pipeline authors. I have left a couple of comments. Please address them before we can merge this since this is marked as implementable. Thanks again!

/approve

JeromeJu

The proposal LGTM, just some small questions.

teps/0145-cel-in-whenexpression.md

JeromeJu · 2023-10-13T14:45:05Z

teps/0145-cel-in-whenexpression.md

+- Explicitly document that passing CEL expression from param is not allowed and won’t be executed.
+
+The solution we proposed is to let CEL handle the variable substitution:
+1. Add params, results, context variables to CEL's environment, similar like [Tekton Triggers](https://github.com/tektoncd/triggers/blob/main/pkg/interceptors/cel/cel.go#L104C1-L112)


I think the tekton trigger examples are nice to add. Would you mind also clarifying the environment here?

I added link to the cel environment, it would add too many details here if we want to add code snippets.

teps/0145-cel-in-whenexpression.md

tekton-robot · 2023-10-13T16:09:18Z

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teps/0145-cel-in-whenexpression.md

This commit adds the proposal of adding CEL in WhenExpression Signed-off-by: Yongxuan Zhang [email protected]

jerop

Merging offline as we have all the approvals 🚀

/lgtm

Thank you @Yongxuanzhang 🎉

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[TEP-0138]: Decouple API and Feature Versioning Proposal #1034

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[TEP-0145] CEL in WhenExpression

e27777f

This commit adds the proposal of adding CEL in WhenExpression Signed-off-by: Yongxuan Zhang [email protected]

Yongxuanzhang force-pushed the tep-144 branch from a035184 to e27777f Compare October 13, 2023 17:36

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tekton-robot merged commit 3725139 into tektoncd:main Oct 13, 2023
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[TEP-0145] CEL in WhenExpression #1074

[TEP-0145] CEL in WhenExpression #1074

Yongxuanzhang commented Sep 28, 2023

Yongxuanzhang commented Sep 28, 2023

JeromeJu commented Oct 2, 2023

jerop commented Oct 2, 2023

JeromeJu commented Oct 2, 2023

JeromeJu commented Oct 2, 2023

QuanZhang-William left a comment

QuanZhang-William Oct 2, 2023

Yongxuanzhang Oct 3, 2023

Yongxuanzhang Oct 12, 2023

Yongxuanzhang commented Oct 12, 2023

pritidesai Oct 13, 2023

Yongxuanzhang Oct 13, 2023

Yongxuanzhang Oct 13, 2023

pritidesai Oct 13, 2023

Yongxuanzhang Oct 13, 2023

Yongxuanzhang Oct 13, 2023

Yongxuanzhang Oct 13, 2023

pritidesai commented Oct 13, 2023

JeromeJu left a comment

JeromeJu Oct 13, 2023

Yongxuanzhang Oct 13, 2023

tekton-robot commented Oct 13, 2023

jerop left a comment


		The new fields will be gated by a new feature flag, `enable-cel-whenexpression`, which will defaults to `"false"` while the feature is in alpha.

		The validation webhook will validate either the current when `input`+`operator`+`values` or `cel` is used, users cannot use both at the same time for one `WhenExpression`.


		### Variables Substitution

		The CEL in When Expressions should support current Tekton’s Params and Results [string substitutions](https://github.com/tektoncd/pipeline/blob/main/docs/variables.md#variables-available-in-a-pipeline). Array and object substitutions are not supported because Tekton doesn’t support whole array/object replacements in a string.

[TEP-0145] CEL in WhenExpression #1074

[TEP-0145] CEL in WhenExpression #1074

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Yongxuanzhang commented Sep 28, 2023

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