Terraform ignore_changes and 'A static list expression is required.

Including dynamic blocks or a for_each resource with ignore_changes leads to: A static list expression is required. As for the solution, make sure whatever list of attributes you are passing to ignore_changes to be static.

Prerequisites

• Terraform

Solution

Taking the following code block into consideration:

resource "aws_instance" "this" {
  ami           = "ami-0c55b159cbfafe1f0"
  instance_type = "t2.micro"

  dynamic "ebs_block_device" {
    for_each = var.ebs_volumes

    content {
      device_name = ebs_block_device.value.device_name
      volume_type = ebs_block_device.value.volume_type
      volume_size = ebs_block_device.value.volume_size
    }
  }

  lifecycle {
    ignore_changes = [ebs_block_device]
  }
}

The fix:

lifecycle {
  ignore_changes = [ebs_block_device.*.device_name, ebs_block_device.*.volume_type, ebs_block_device.*.volume_size]
}

Note: The wildcard (*) in ebs_block_device.*.device_name and the rest, creates a list of all values of the specified attribute for all instances of the dynamic block.

Conclusion

Related: Resolve: “The block type lifecycle is reserved for use by Terraform in a future version”.

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