## Description `terraform test` fails when using `override_data` with `values` for data sources that use the Plugin Framework's `nested_type` schema representation. HCL list literals (`[{ ... }]`) produce tuple types, and `fillAttribute` in the mocking package rejects them with: ``` Error: Failed to compute attribute Terraform could not compute a value for the target type list of object with the mocked data with the attribute ".result": incompatible types; expected object type, found tuple. ``` This makes `terraform test` mocking unusable for providers built entirely with the Plugin Framework — most notably Cloudflare provider v5, which has 397 resources/data sources using `nested_type`. The bug is in the `fillAttribute` function and is unrelated to `override_during` — it triggers with or without it. ## Root cause In `internal/moduletest/mocking/fill.go`, `fillAttribute` checks `in.Type().IsObjectType()` **before** inspecting the nesting mode. For `NestingSingle`/`NestingGroup` this is correct, but for `NestingList`/`NestingSet`/`NestingMap` the input value is a collection (tuple/list/set/map), not an object. The existing `fillType` function already handles tuple→list coercion correctly for `type`-based schemas (SDKv2 providers), but the `fillAttribute` path for `nested_type` schemas (Plugin Framework providers) does not. ## Reproduction Tested on Terraform v1.11.4 and v1.14.3, Cloudflare provider v5.18.0. **Note:** OpenTofu v1.11.5 does NOT have this bug — same test passes there. ### Cloudflare (FAILS) ```hcl # main.tf terraform { required_providers { cloudflare = { source = "cloudflare/cloudflare" version = "~> 5.0" } } } data "cloudflare_accounts" "this" {} output "account_id" { value = data.cloudflare_accounts.this.result[0].id } output "account_name" { value = data.cloudflare_accounts.this.result[0].name } ``` ```hcl # tests/mock_accounts.tftest.hcl mock_provider "cloudflare" { override_data { target = data.cloudflare_accounts.this values = { result = [ { id = "fake-account-id-1234" name = "Test Account" type = "standard" created_on = "2024-01-01T00:00:00Z" managed_by = { parent_org_id = "" parent_org_name = "" } settings = { abuse_contact_email = "" enforce_twofactor = false } }, ] } } } run "plan_with_mocked_accounts" { command = plan assert { condition = output.account_id == "fake-account-id-1234" error_message = "Expected mocked account ID" } assert { condition = output.account_name == "Test Account" error_message = "Expected mocked account name" } } ``` ``` $ terraform test run "plan_with_mocked_accounts"... fail │ Error: Failed to compute attribute │ ...incompatible types; expected object type, found tuple. Failure! 0 passed, 1 failed. ``` ### AWS (PASSES) — same pattern, same Terraform version The identical `override_data` pattern works for AWS provider because it uses `type`-based schema (SDKv2) instead of `nested_type`: ```hcl # main.tf data "aws_caller_identity" "this" {} output "account_id" { value = data.aws_caller_identity.this.account_id } ``` ```hcl # tests/mock_identity.tftest.hcl mock_provider "aws" {} run "plan_with_mocked_identity" { command = plan override_data { target = data.aws_caller_identity.this values = { account_id = "123456789012" } } assert { condition = output.account_id == "123456789012" error_message = "Expected mocked AWS account ID" } } ``` ``` $ terraform test Success! 1 passed, 0 failed. ``` ### Schema difference The key difference visible in `terraform providers schema -json`: - **AWS** (works): flat `"type": "string"` attributes — processed by `fillType` which handles tuple→list coercion - **Cloudflare v5** (fails): `"nested_type"` with `"nesting_mode": "list"` — processed by `fillAttribute` which lacks collection handling ## Impact Any provider built entirely with the Plugin Framework that uses `ListNestedAttribute`, `SetNestedAttribute`, or `MapNestedAttribute` will be affected. The Cloudflare v5 provider has 214 data sources with `nested_type` list attributes and zero with `type`-based list attributes, making `terraform test` mocking effectively unusable for it. ## Proposed fix PR: #38370 Move the object type check into `NestingSingle`/`NestingGroup` only, and add collection iteration for `NestingList`/`NestingSet`/`NestingMap` that fills each element against the nested attribute schema — matching how `fillType` already handles this for `type`-based attributes. ## Environment - Terraform: v1.11.4, v1.14.3 - Cloudflare provider: v5.18.0 - AWS provider: v5.x (control test) - OpenTofu: v1.11.5 (not affected) - OS: Linux x86_64 --- *This issue was generated with [Claude Code](https://claude.ai/code)*