[WIP] Introducing v1experimental

[slinkydeveloper]

Signed-off-by: Francesco Guardiani francescoguard@gmail.com

Testing the feasibility of the idea from https://docs.google.com/document/d/1jluAYCJi6kq6HBmR7uMRUB7Zxcf1v6qjR3-pw0gMTRU/edit?usp=sharing

This PR introduces a new api group version called v1experimental. This api group is not stored and the webhook converts it back to v1, in order to avoid duplicating controller code. Experimental code, through api conversion, can retrieve the experimental fields. This PR implements the "compile time feature gates" aka the experimental features code is not compiled in stable releases.

This is how you use the experimental feature in the controller https://github.com/knative/eventing/pull/4279/files#diff-8ae7187e03db920a4f61e06aa3bcbbbe

This is how the v1experimental looks like when it's stored:

Name:         my-service-trigger
Namespace:    default
Labels:       eventing.knative.dev/broker=default
Annotations:  eventing.knative.dev/creator: kubernetes-admin
              eventing.knative.dev/lastModifier: kubernetes-admin
              v1experimental/expression: helloworld
API Version:  eventing.knative.dev/v1
Kind:         Trigger
Metadata:
  Creation Timestamp:  2020-10-12T08:39:35Z
  Generation:          1
  Managed Fields:
    API Version:  eventing.knative.dev/v1experimental
    Fields Type:  FieldsV1
    fieldsV1:
      f:metadata:
        f:annotations:
          .:
          f:kubectl.kubernetes.io/last-applied-configuration:
      f:spec:
        .:
        f:broker:
        f:filter:
          .:
          f:expression:
        f:subscriber:
          .:
          f:ref:
            .:
            f:apiVersion:
            f:kind:
            f:name:
    Manager:      kubectl-client-side-apply
    Operation:    Update
    Time:         2020-10-12T08:39:35Z
    API Version:  eventing.knative.dev/v1
    Fields Type:  FieldsV1
    fieldsV1:
      f:status:
        f:conditions:
        f:observedGeneration:
    Manager:         mtchannel_broker
    Operation:       Update
    Time:            2020-10-12T08:39:35Z
  Resource Version:  16802
  Self Link:         /apis/eventing.knative.dev/v1/namespaces/default/triggers/my-service-trigger
  UID:               6503fe3e-0e14-4ab9-bca7-02dde28f5325
Spec:
  Broker:  default
  Filter:
  Subscriber:
    Ref:
      API Version:  serving.knative.dev/v1
      Kind:         Service
      Name:         my-service
      Namespace:    default

As you can see, annotations are used to store v1experimental fields

Proposed Changes

• New experimental API group called v1experimental
• New feature build flag called js_trigger_filter (just for demonstration purpose)

Problems

• deepcopy-gen doesn't like golang tags. This has to be fixed before shipping this PR

TBD

Docs

TBD

[knative-prow-robot]

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[codecov]

Codecov Report

Merging #4279 into master will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master    #4279   +/-   ##
=======================================
  Coverage   80.36%   80.37%           
=======================================
  Files         288      289    +1     
  Lines        7910     7912    +2     
=======================================
+ Hits         6357     6359    +2     
  Misses       1172     1172           
  Partials      381      381           

Impacted Files	Coverage Δ
...g/reconciler/mtbroker/trigger/expression_stable.go	100.00% <100.00%> (ø)
pkg/reconciler/mtbroker/trigger/trigger.go	73.28% <100.00%> (+0.20%)	⬆️

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[knative-metrics-robot]

The following is the coverage report on the affected files.
Say /test pull-knative-eventing-go-coverage to re-run this coverage report

File	Old Coverage	New Coverage	Delta
pkg/reconciler/mtbroker/trigger/expression_stable.go	Do not exist	100.0%
pkg/reconciler/mtbroker/trigger/trigger.go	80.0%	80.2%	0.2

[knative-prow-robot]

@slinkydeveloper: PR needs rebase.

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[github-actions]

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inactivity. Reopen with /reopen. Mark as fresh by adding the
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[knative-prow-robot]

@slinkydeveloper: The following tests failed, say /retest to rerun all failed tests:

Test name	Commit	Details	Rerun command
pull-knative-eventing-upgrade-tests	0c66be1	link	/test pull-knative-eventing-upgrade-tests
pull-knative-eventing-go-coverage	0c66be1	link	/test pull-knative-eventing-go-coverage
pull-knative-eventing-reconciler-tests	0c66be1	link	/test pull-knative-eventing-reconciler-tests

Full PR test history. Your PR dashboard.

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[pierDipi]

Can we close this one since we've adopted #5404?