Note: The issue of map transform failing is just one example of a case where rendering can fail. The real issue is that any rendering error isn't visible for the user interacting with the claim.

What happened?

When patching with a Map transform, if the key doesn't exist it silently fails to apply the patch (snippet below).

The composition will stay not ready, with a spec only with 1 condition:

  conditions:
    - lastTransitionTime: '2022-08-23T15:09:44Z'
      reason: Creating
      status: 'False'
      type: Ready

Only in the logs we can see that it fails applying with an error like this:

1.6612685509865906e+09	DEBUG	crossplane.events	Warning	{"object": {... "reason": "ComposeResources", "message": "cannot render composed resource from resource template at index 2: cannot apply the patch at index 6: transform at index 0 returned error: map transform could not resolve: key asdf is not found in map"}

tl;dr: "map transform could not resolve: key asdf is not found in map"

(this error also is only visible when enabling the debug flag in the args for the crossplane container, e.g. core start --debug)

I would expect that the composition receives an additional status condition with the error message, so that it's easier to notice an error when rendering. I consider seeing no errors or status conditions like this by default as a "silent ignore" and therefore a bug, as it's not user friendly to troubleshoot.

(kubectl describe <the-composition> does list the warning as an event though, but it's not propagated to the claim.)

How can we reproduce it?

Composition with patch and a map transform with specific set of keys, like this:

- type: FromCompositeFieldPath
  fromFieldPath: spec.parameters.region
  toFieldPath: spec.forProvider.region
  transforms:
    # Any other value from spec.parameters.region result in an silent error.
    - type: map
      map:
        rma: Rümlang
        lpg: Lupfig

Then, in the claim's parameter, set a value that doesn't exist in the above map (neither rma nor lpg).

What environment did it happen in?

Crossplane version: v1.9