ibm_pi_host_group: Update crashes with "interface {} is *schema.Set, not []interface {}"

[jreeves-lus]

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Terraform CLI and Terraform IBM Provider Version

Affected Resource(s)

• ibm_pi_host_group (PowerVS)

Terraform Configuration Files

Please include all Terraform configurations required to reproduce the bug. Bug reports without a functional reproduction may be closed without investigation.

terraform-provider-ibm: v 1.88.2
I also attempted 1.88.1, 1.88.0, and 1.75.2 (which was before update to the source file), all resulted in the same error.

# Minimal repro (redacted)
resource "ibm_pi_host_group" "example" {
  pi_cloud_instance_id = var.pi_cloud_instance_id

  # Host group name
  pi_name = "test-host-group"

  # (A) Hosts in the group
  pi_hosts = [
    {
      display_name = "host-1"
      sys_type     = "s922"
    }
  ]

  # (B) Share with a secondary workspace – toggling this triggers Update
  pi_secondaries = [
    {
      name      = "test-host-group-secondary"
      workspace = var.secondary_workspace_id
    }
  ]
}

Debug Output

https://gist.github.com/jreeves-lus/b9f3330a4d3e5bea4a63001ddf86fde0

Panic Output

https://gist.github.com/jreeves-lus/fe6f648d09031c4f3ad8cfb76b52eded

Expected Behavior

Provider should handle the update of nested list attributes (pi_hosts, pi_secondaries) without crashing.

Actual Behavior

Terraform fails with a provider panic during update.

Steps to Reproduce

Steps to reproduce:

1. Apply the configuration above to create a host group.
2. Change one of the nested list values - 3.g. remove/add an entry in pi_secondaries or pi_hosts
3. Run terraform apply
4. Provider crashes during Update

module.powervs_workspace.ibm_pi_host_group.dedicated_hosts: Modifying... [id=<redacted>]
│ Error: Request cancelled
│ The plugin.(*GRPCProvider).ApplyResourceChange request was cancelled.

Stack trace from the terraform-provider-ibm_v1.88.2 plugin:

panic: interface conversion: interface {} is *schema.Set, not []interface {}

goroutine 46 [running]:
github.com/IBM-Cloud/terraform-provider-ibm/ibm/service/power.resourceIBMPIHostGroupUpdate({0x6e1f108, 0xc0004a17a0}, 0xc0043483f0, {0x628c940, 0xc000307c08})
        github.com/IBM-Cloud/terraform-provider-ibm/ibm/service/power/resource_ibm_pi_host_group.go:237 +0xab1
...
Error: The terraform-provider-ibm_v1.88.2 plugin crashed!

Important Factoids

Panic suggests an interface type assertion mismatch in the update handler (treats a *schema.Set as []interface{}. The resource and its implementation are in the PowerVS package (ResourceIBMPIHostGroup.

References

Documentation shows that pi_hosts and pi_secondaries are a List type:
https://registry.terraform.io/providers/IBM-Cloud/ibm/latest/docs/resources/pi_host_group

Location of Update handler:
https://github.com/IBM-Cloud/terraform-provider-ibm/blob/master/ibm/service/power/resource_ibm_pi_host_group.go

• #0000

[michaelkad]

@jreeves-lus I have opened #6677 to address #6672 -- fell free to close your PR.