hashicorp/terraform · error

%q attribute is read-only

Error message

%q attribute is read-only

What it means

Returned by validateDataStoreResourceConfig at resource_data.go:89 when validating a terraform_data data resource. Core does not currently reject computed attributes set in config, so this provider explicitly checks the 'id' and 'output' attributes and reports each as read-only. 'output' is the computed result of terraform_data and 'id' is its computed identity; neither may be supplied by the user.

Source

Thrown at internal/builtin/providers/terraform/resource_data.go:89

					Description: "The unique identifier for the data store.",
					Required:    true,
				},
			},
			Nesting: configschema.NestingSingle,
		},
	}
}

func validateDataStoreResourceConfig(req providers.ValidateResourceConfigRequest) (resp providers.ValidateResourceConfigResponse) {
	if req.Config.IsNull() {
		return resp
	}

	// Core does not currently validate computed values are not set in the
	// configuration.
	for _, attr := range []string{"id", "output"} {
		if !req.Config.GetAttr(attr).IsNull() {
			resp.Diagnostics = resp.Diagnostics.Append(fmt.Errorf(`%q attribute is read-only`, attr))
		}
	}
	return resp
}

func upgradeDataStoreResourceState(req providers.UpgradeResourceStateRequest) (resp providers.UpgradeResourceStateResponse) {
	// We've only added new nullable block attributes, so unmarshaling from json
	// will complete the data structure correctly.
	val, err := ctyjson.Unmarshal(req.RawStateJSON, dataStoreResourceSchema().Body.ImpliedType())
	if err != nil {
		resp.Diagnostics = resp.Diagnostics.Append(err)
		return resp
	}

	resp.UpgradedState = val
	return resp
}

View on GitHub (pinned to c9def3e214)

Solutions

1. Remove the id and/or output attributes from the data "terraform_data" block; both are computed.
2. If you need to pass input, use the input attribute (arbitrary value) of terraform_data.

Example fix

// before
data "terraform_data" "example" {
  input = local.value
  id    = "fixed-id"
}

// after
data "terraform_data" "example" {
  input = local.value
}

// Before applying, lint terraform_data blocks for settable computed attrs.
var dataBlocks []cty.Value // parsed config blocks of terraform_data
readOnly := map[string]bool{"id": true, "output": true}
for _, b := range dataBlocks {
    for attr := range readOnly {
        if v := b.GetAttr(attr); !v.IsNull() {
            return fmt.Errorf("terraform_data: %q is read-only", attr)
        }
    }
}

When it happens

Trigger: A terraform_data block whose body sets output = ... or id = ... (e.g. data "terraform_data" "x" { id = "abc" }).

Common situations: Copy-pasting a managed-resource pattern into terraform_data; trying to feed a known output back in; assuming id is settable like on some resources.

Related errors

• Cannot set both 'source' and 'content'
• Must provide one of 'source' or 'content'
• source and content cannot both be null
• invalid null string in 'scripts'
• invalid empty string in 'scripts'

AI-assisted analysis of hashicorp/terraform@c9def3e214 (2026-08-07). Data as JSON: /api/errors/51522a69f8ba4fb1. Report an issue: GitHub.