Parsing JSON strings in CEL interceptors

[jace-ys]

Expected Behavior

It will be really useful if we could parse JSON strings in CEL interceptors, when we get a payload containing a JSON string field.

Actual Behavior

When my EventListener receives deployment webhooks from GitHub, that JSON object contains a payload field that's a JSON string (not sure why GitHub does this 😓). Example:

{
  "action": "created",
  "deployment": {
    "url": "https://api.github.com/repos/Codertocat/Hello-World/deployments/145988746",
    "id": 145988746,
    "node_id": "MDEwOkRlcGxveW1lbnQxNDU5ODg3NDY=",
    "sha": "f95f852bd8fca8fcc58a9a2d6c842781e32a215e",
    "ref": "master",
    "task": "deploy",
    "payload": "{\"hello\": \"world\"}", # this JSON string
    "original_environment": "production",
    "environment": "production",
    ...
  }
}

I would ideally like to do something like this in my interceptor body.deployment.payload.hello == 'world' , but since payload isn't treated as an object, I have to do body.deployment.payload == '{"hello": "world"}' which isn't great once i have a larger payload field.

Steps to Reproduce the Problem

1. Send the above webhook payload to an EventListener containing a field with a JSON string
2. Parse the body.deployment.payload.hello == 'world'
3. EventListener doesn't evaluate the above statement to true

Additional Info

[dibyom]

/kind feature

[dibyom]

Fixed in #537

[dibyom]

/milestone 0.5

[dibyom]

/close

[tekton-robot]

@dibyom: Closing this issue.

In response to this:

/close

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.