Proposal: Common Expression Language Custom Task (CELRun)

[jerop]

Proposal for creating tektoncd/experimental/cel to incubate Common Expression Language Custom Tasks project

Per process, this project was proposed with verbal support at the Tekton WG on Jan 13th 2021

The problem the project will solve

CEL Custom Tasks will allow us to experiment with CEL in Tekton Pipelines without adding CEL directly to the Tekton API surface

CEL Custom Tasks would be useful in evaluating more complex expressions for guarding execution of Tasks beyond what we support in WhenExpressions, read more

Related issues:

• Common Expression Language Custom Task pipeline#3149
• Feature: expression support in $()  pipeline#2812
• Feature: method to absorb git-source yaml into Pipeline/Task $inputs etc pipeline#2219
• Simple if/conditional support for skipping pipeline#2127
• Consider removing type from params (or _really_ support types) pipeline#1393

Who will own it

• @jerop
• @bobcatfish
• @pritidesai
• @imjasonh
• @bigkevmcd

Updates

• Project: https://github.com/tektoncd/experimental/tree/master/cel
• TEP: TEP-0043: Common Expression Language Custom Task (CELRun) #314

/cc Governing Board: @abayer @vdemeester @bobcatfish @afrittoli @imjasonh

[afrittoli]

+100

This would be useful to simplify how we use conditions today in dogfooding, so I'd be happy to start running the custom task controller in dogfooding from the experimental repo.

[imjasonh]

+1, happy to co-own and help update and contribute cel-task as a base (or start from scratch if that's better).

🎉

[jerop]

+1, happy to co-own and help update and contribute cel-task as a base (or start from scratch if that's better).

yes yes, we can build on it, thanks for your contributions @imjasonh!

some changes I propose we make include:

• when the CEL expression is valid and is evaluated successfully, the ConditionSucceeded in status of the CELRun is set to True regardless of the expression evaluation result and the CELRun produces a Result representing the expression evaluation result (True/False)
• when the CEL expression is invalid or any other error is encountered, the ConditionSucceeded in status of the CELRun is set to False

this will allow us to distinguish between errors and the expression evaluating to false, which was one of the issues with Conditions

[imjasonh]

some changes I propose we make include:

Yeah those both sound like good improvements. 👍

[jerop]

thanks for the quick review @imjasonh and @afrittoli

created the project folder in tektoncd/experimental#691

[jerop]

Common Expression Language Custom Tasks is available in https://github.com/tektoncd/experimental/tree/master/cel

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