How to get latest sintax of cel and most new api features?

[alansenairj]

The tail of documentation is too long and very spread. It is very hard to use just oficial documentation to get more reference to apply filters and overlays.
If I start to using cel sintax from Google course it crashes too much.
It is realy hard to create and manipulate and learn it. How can I use a better sintax?
I discovered extensions using by a blog.
Other guy is declaring api inside cel kind field. Where he get it?
What is the most oficial source to keep me informed about updates and improvments?

[bigkevmcd]

@alansenairj What would you like to see added?

The Tekton docs link to the upstream documentation https://tekton.dev/docs/triggers/cel_expressions/#cel-go-extensions which includes the libraries?

The cel-eval tool can be a bit tricky, but it will make it easier to debug your expressions.

There are a lot of examples in the tests for the CEL interceptor https://github.com/tektoncd/triggers/blob/main/pkg/interceptors/cel/cel_test.go

And there are some examples in the repository

triggers/examples/v1beta1/trigger-ref/trigger.yaml

Line 12 in d308fd2

- name: "overlays"

Which Google course are you following?

[alansenairj]

Hi, thanx for your reply.

this one info was crucial for me. I was wrong about documentation. It was there. Thank you.

"Accessing data added by Interceptors
An interceptor can add additional useful data that can be used by a TriggerBinding. Data added by interceptors can be accessed under the top-level extensions field e.g. $(extensions.field-name). In the following example, the CEL interceptor adds a field that is then accessed by the trigger binding:"

About cel expressions, it is hard to work with. But I see advantage in its use so I was insisting to understand it and now I can put it to work. Their learning curve is hard.

The way yaml encapsulates cel expression syntax was the problem for me when I am trying to learn it.

And I think logs are very polluted and I did a ternary evaluation to test and print some output to get it more visible but that is not the way it works. I am not a programmer, I am learning but I will show to you a thing I tried to do:

                - key: namespace
                  expression: |
                    body.ref == 'refs/heads/develop' ? 'portal-web-desenv' :
                    (body.ref == 'refs/heads/master' ? 'portal-web-prd' :
                    (body.ref == 'refs/heads/homolog' ? 'portal-web-hom' :
                    '---erro: branch não permitida-----'))

I am expecting some error in log to get it more visible. But it just filters and it not transforms values nesting those conditions there. But I think it could be easier to test if I could get some better message in log indicating my filter works.

Google course is : https://codelabs.developers.google.com/codelabs/cel-go?hl=pt-br#0

[bigkevmcd]

That looks like an overlay expression, in which case, do you not see the overlay field extensions.namespace if it evaluates successfully.

I am looking at the possibility of using a CEL extension to let you "bind" variables before evaluating the expression.

This might simplify this sort of long-expression that is hard to read and debug.

The basic idea is that you'd do something like:

    interceptors:
    - name: "validate body and add field"
      ref:
        name: "cel"
      params:
      - name: "bindings"
        value:
          - name: isDevelop
            value: body.ref == 'refs/heads/develop'
          - name: isMaster
            value: body.ref == 'refs/heads/master'
      - name: "overlays"
        value:
        - key: namespace
          expression: isDevelop ? 'portal-web-desenv' : isMaster ? 'portal-web-prd'

This isn't implemented yet but I have an experimental branch.

It's where I think things could go (and make use of a CEL extension for doing this) and it might help simplify long complex expressions.

[alansenairj]

This one will be powerfull because I was trying exactly to write some type of result with pre computed variable from earlier sentence.

I will show to you some tries and some not working results.

I was trying to process a namespace using branch name to create just one event listner to work with all "prefix" named applications filtering by branches. If some push came from "master" it should give me a namespace as result.
I don't know if it was a good way to work but I solved it declaring some kind of hardcoded sentence to avoid to create tasks to clone and to do some regex and upload it to git again. If I use EL I was thinking it could be more faster and straight forward.

In operator
https://github.com/google/cel-spec/blob/master/doc/langdef.md#aggregate-values ---using in operator

- key: namespace
  expression: |
    body.ref.split('/')[2] in ['develop', 'master', 'homolog'] ?
    'portal-server-' + (body.ref.split('/')[2] == 'develop' ? 'desenv' :     (sufix namespace)
                       (body.ref.split('/')[2] == 'master' ? 'prd' : 'hom')) :        (append sufix namespace)
    'branch nmot allowed. message'
    

I was trying to use a prefix and append a sulfix as result to create a target namespace.
It crashes and I think I was trying to do too much thing there.

another thing I got problem was this:

  - key: namespace
  expression: |
    (
      body.ref.split('/')[2] == 'develop' ? 'portal-server-desenv' :
      (
        body.ref.split('/')[2] == 'master' ? 'portal-server-prd' :
        (
          body.ref.split('/')[2] == 'homolog' ? 'portal-server-hom' :
          'branch não permitida. message'
        )
      )
    )

this formatting is totally rejected. But sorry if it was some beginner error. this syntax I said I learnt in google course. It was rejected.