Organizations: add `ListParents` (OU/account parent read-back for Terraform)

[b-rajesh]

AWS Service name

Organizations

Operations needed

• ListParents(ChildId) — ChildId is an ou-* id or an account id. Read the stored parent and return the single parent AWS returns:
  { "Parents": [ { "Id": "<parent_id>", "Type": "ROOT" | "ORGANIZATIONAL_UNIT" } ] }
  (Type = ROOT when the parent id starts with r-, else ORGANIZATIONAL_UNIT). Return ChildNotFoundException for an unknown ChildId.

Use case

A multi-OU Terraform/OpenTofu build (aws_organizations_organizational_unit) creates OUs via CreateOrganizationalUnit (already supported), but the provider's Read then calls ListParents to populate parent_id — real-AWS DescribeOrganizationalUnit doesn't return the parent, so the provider must ListParents the child, and in SDKv2 this fires on every create and refresh. ListParents isn't implemented, so apply errors on the read-back (InvalidAction: Operation 'ListParents' not implemented): nested OUs never get created, outputs are empty, idempotency is unreachable. This single read op unblocks the whole OU-hierarchy flow locally. (It also covers the account read-back needed if CreateAccount/MoveAccount are added later.)

Would you like to contribute this?

• Yes, I'd like to implement this service and open a PR
• I can help review/test an implementation

[b-rajesh]

Proof

Verified against a clean MiniStack v1.3.69 (Terraform 1.5.7 + hashicorp/aws ~> 5.0, provider endpoints { organizations = "http://localhost:4566" }).

CreateOrganizationalUnit is already supported, so the OU is created in MiniStack — but the provider's Read immediately calls ListParents (real-AWS DescribeOrganizationalUnit doesn't return the parent), which is absent, so apply errors on the read-back.

# parent_id from: aws --endpoint-url http://localhost:4566 organizations list-roots --query 'Roots[0].Id'
resource "aws_organizations_organizational_unit" "team" {
  name      = "team-ou"
  parent_id = var.root_id
}

resource "aws_organizations_organizational_unit" "team_dev" {
  name      = "team-dev-ou"
  parent_id = aws_organizations_organizational_unit.team.id
}

aws_organizations_organizational_unit.team: Creating...

Error: listing Organizations Organizational Unit (ou-b4cb-3342e74658) parents:
operation error Organizations: ListParents, https response error StatusCode: 400,
api error InvalidAction: Operation 'ListParents' not implemented

The OU is created in MiniStack (CreateOrganizationalUnit succeeds), but apply fails on the post-create ListParents read-back — so the nested team-dev-ou is never created, terraform output is empty, and a re-apply re-hits the same missing op (idempotency unreachable). Direct call confirms the op is absent:

ListParents {"ChildId":"ou-..."} -> InvalidAction: Operation 'ListParents' not implemented