Using Bitbucket Cloud as the Git provider and Pipelines-as-Code (PAC) version v0.37.3, CEL expressions fail to evaluate even when using the simplest possible expression (e.g., "true"). A PipelineRun annotated with "pipelinesascode.tekton.dev/on-cel-expression: true" is skipped, and the PAC controller logs a parsing error.

The following error appears in the openshift-pipelines/pipelines-as-code-controller-* pod when a Bitbucket Cloud push event is received:

there was an error evaluating the CEL expression, skipping: json: cannot unmarshal string into Go value of type map[string]interface {}

Full log excerpt:
{"level":"error","logger":"pipelinesascode","msg":"there was an error evaluating the CEL expression, skipping: json: cannot unmarshal string into Go value of type map[string]interface {}","commit":"10dee4fce84b750d7597e61d78a420101ab36d78","provider":"bitbucket-cloud","event-type":"push","target-branch":"test-cel","namespace":"phx","stacktrace":"github.com/openshift-pipelines/pipelines-as-code/pkg/matcher/annotation_matcher.go:282 ..."}

Environment:

• PAC version: v0.37.3

• Git provider: Bitbucket Cloud

• Event type: push

• Simple CEL expression used:
  pipelinesascode.tekton.dev/on-cel-expression: |
  true

Steps to reproduce:

1. Configure a Bitbucket Cloud repository with a push webhook pointing to PAC.

1. Add a PipelineRun containing a CEL expression under the .tekton directory. Example:
   pipelinesascode.tekton.dev/on-cel-expression: |
   true

1. Push a commit to the repository.

1. Observe that the PipelineRun is skipped and the controller logs an unmarshalling error.

Actual behavior:

• PAC throws a JSON unmarshalling error when evaluating the CEL expression.

• The PipelineRun is skipped.

• CEL evaluation does not work for Bitbucket Cloud push events.

Expected behavior:

• CEL expressions should evaluate correctly for Bitbucket Cloud webhook events.

• Simple expressions such as "true" should not fail.

• PipelineRuns should be triggered based on CEL conditions.

Impact:

• CEL-based filtering cannot be used with Bitbucket Cloud.

• Conditional execution of PipelineRuns is broken.

• Workflows depending on CEL conditions cannot be implemented.

Request:
Please investigate and fix the CEL expression parsing issue for Bitbucket Cloud events in PAC v0.37.3, or clarify whether CEL support was expected to work for Bitbucket Cloud in this version.