Can't supply container registry credentials to Container App.

Something is up with the Container App / Container Registry integration. I could swear that this worked a month or so ago, but I tried creating a new container app service today. This is the offending line:

containerApp {
    reference_registry_credentials [ Arm.ContainerRegistry.registries.resourceId mySuperRegistry.Name ]
}

where mySuperRegistry is an Azure container registry that already exists.

When I try an deploy the container app, I get the following validation error:

{'code': 'ContainerAppInvalidPropertyValue', 'message': "Property 'secrets.name' has an invalid value '[listCredentials(resourceId('Microsoft.ContainerRegistry/registries', 'mySuperRegistry'), '2019-05-01').username]'. A value must consist of lower case alphanumeric characters, '-'
 or '.', and must start and end with an alphanumeric character."}
)

Here’s an extract of the raw ARM template:

          "registries": [
            {
              "passwordSecretRef": "[listCredentials(resourceId('Microsoft.ContainerRegistry/registries', 'mySuperRegistry'), '2019-05-01').username]",
              "server": "[reference(resourceId('Microsoft.ContainerRegistry/registries', 'mySuperRegistry'), '2019-05-01').loginServer]",
              "username": "[listCredentials(resourceId('Microsoft.ContainerRegistry/registries', 'mySuperRegistry'), '2019-05-01').username]"
            }
          ],
          "secrets": [
            {
              "name": "[listCredentials(resourceId('Microsoft.ContainerRegistry/registries', 'mySuperRegistry'), '2019-05-01').username]",
              "value": "[listCredentials(resourceId('Microsoft.ContainerRegistry/registries', 'mySuperRegistry'), '2019-05-01').passwords[0].value]"
            }
          ]

It’s almost as though ARM hasn’t seen that secrets.name is an expression, and has instead tried to parse the expression as a raw string.

@ninjarobot Have you any idea about this - or if this ever used to work? @anthonychu has anything changed in the way that secret names are handled in terms of ARM template support - maybe something has changed since the namespace move?

[anthonychu]

Sounds like it’s the same as this https://github.com/microsoft/azure-container-apps/issues/153

[isaacabraham]

I see! I think it’s the same underlying issue - ARM isn’t evaluating expressions in the template in certain fields.

The fix you’ve put in is of course a really nice workaround, by not using an ARM expression at all.