Bridged resources are not replaced when a nested property is updated on a collection with ForceNew

[VenelinMartinov]

What happened?

Under both TF and Pulumi, a resource is not replaced when updating a property of an element in a ForceNew collection.

Example

[ 
  {nested: val2},
  {nested: val3},
  {nested: val1},
]

to

[ 
  {nested: val2},
  {nested: val4},
  {nested: val1},
]

Does not trigger a replacement of the resource, even if the containing collection is ForceNew.

AWS example by @t0yv0 here: #2726 (comment)

data "aws_ami" "ubuntu" {
  most_recent = true

  filter {
    name   = "name"
    values = ["ubuntu/images/hvm-ssd/ubuntu-jammy-22.04-amd64-server-*"]
  }

  filter {
    name   = "virtualization-type"
    values = ["hvm"]
  }

  owners = ["099720109477"] # Canonical
}


resource "aws_instance" "example" {
  ami           = data.aws_ami.ubuntu.id
  instance_type = "t2.micro"

  root_block_device {
    volume_size = 8
  }

  ephemeral_block_device {
    virtual_name = "ephemeral0"
    device_name  = "/dev/sde"
  }

  ephemeral_block_device {
    virtual_name = "ephemeral3" # tweak this
    device_name  = "/dev/sdf"
  }
}

Related TF discussions hashicorp/terraform-plugin-sdk#1314 and hashicorp/terraform#34691

Note also that the SDKv2 Schema validation is slightly off in a related way: #2723 (comment)

Output of pulumi about

.

Additional context

No response

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[VenelinMartinov]

Closing as intended.

In TF collections of plain elements are replaced when the number of elements changes or one of the element changes.

Collections of objects are replaced when the number of elements changes. Changing a property of an element does not trigger the collection to be replaced.

[t0yv0]

Collections of objects are replaced when the number of elements changes

Couple of additional information here.

1. I've confirmed that current Pulumi provider matches TF behavior on the ephemeral_block_device example.

2. The same instance example can be used to try lists of MaxItems=1 objects, for example:

  private_dns_name_options {
     enable_resource_name_dns_a_record = true
  }

I have confirmed that both Pulumi and TF generate update plans when tweaking these.

So then, it would indeed appear that collection-level ForceNew on List[{"x": X}] and Set[{"x": X}] does not trigger replacements. when an element's property changes, but it would trigger replacements for simple types like List[string].

Indeed this appears to be by-design we need to match.