Creating a Greengrass Group with a device generates incorrect Cloudformation output.

[kennycoder]

Using your example as base code I modified it slightly to add a thing into the group:

let a_s = new iot.CfnThing(this, 'a_sensor', {
          thingName: 'MyThingSensor',
        })
       let a_group = new gg.Group(this, 'a_group', {
            core: new gg.Core(this, 'a_core', {
                thing: a_t,
                syncShadow: true,
                certificateArn: props.certificateArnCore
            }),
            devices: [new gg.Device(this, 'a_sensor_device', {
              thing: a_s,
              syncShadow: false,
              certificateArn: props.certificateArnSensor
            })],
            functions: [gg_lambda],
            subscriptions: subscriptions,
            loggers: [localLogger],
            resources: [tmp_folder]
        })

Unfortunately this fails with the following error during deployment:

AwsBlueprintIotStack failed: ValidationError: Template error: resource asensor does not support attribute type arn in Fn::GetAtt
Template error: resource asensor does not support attribute type arn in Fn::GetAtt

After looking into CF template output I noticed the following:

"agroupagroupdevicesA720B9C5": {
      "Type": "AWS::Greengrass::DeviceDefinition",
      "Properties": {
        "Name": "a_group",
        "InitialVersion": {
          "Devices": [
            {
              "CertificateArn": "arn:aws:iot:eu-central-1:980409644593:cert/263d1b96d60b71109613cedd6c3b701e96a99d706b9f622db2161d099ab21e62",
              "Id": "a_sensor_device",
              "SyncShadow": false,
              "ThingArn": {
                "Fn::GetAtt": [
                  "asensor",
                  "arn"
                ]
              }
            }
          ]
        }
      },

If you look at the ThingArn it tries to use GetAtt which indeed does not exist. Analyzing the same block of code for the thing that is associated to GG Core, it generated the ARN diffferenly:

...
"ThingArn": {
"Fn::Join": [
  "",
  [
    "arn:",
    {
      "Ref": "AWS::Partition"
    },
    ":iot:",
    {
      "Ref": "AWS::Region"
    },
    ":",
    {
      "Ref": "AWS::AccountId"
    },
    ":thing/MyThingCore"
  ]
]
}
...

And this works. My question is, is this CDK related or related to your CDK constructs? Regards, Nikolai

[massi-ang]

Can you get the latest commit and test it?

[kennycoder]

Works as expected now. Appreciated! Closing.