hashicorp/terraform · critical

Unknown type: %s

Error message

Unknown type: %s

What it means

A panic in `MapFieldReader`-style `readPrimitive` (internal/legacy/helper/schema/field_reader.go:342), default branch when `schema.Type` is not TypeBool/TypeInt/TypeFloat/TypeString. The primitive reader only decodes scalar types, so any other (or invalid) Type reaches the panic with 'Unknown type: %s'. Like 973 this reflects a malformed provider schema, but specifically in the legacy map-backed field-reading path.

Source

Thrown at internal/legacy/helper/schema/field_reader.go:342

	case TypeInt:
		if value == "" {
			returnVal = 0
			break
		}
		if computed {
			break
		}

		v, err := strconv.ParseInt(value, 0, 0)
		if err != nil {
			return nil, err
		}

		returnVal = int(v)
	case TypeString:
		returnVal = value
	default:
		panic(fmt.Sprintf("Unknown type: %s", schema.Type))
	}

	return returnVal, nil
}

View on GitHub (pinned to c9def3e214)

Solutions

1. Audit the provider schema: every field the legacy reader treats as primitive must have Type in {TypeBool, TypeInt, TypeFloat, TypeString}.
2. Set or correct the `Type` on the offending attribute.
3. Add provider schema-construction tests to catch TypeInvalid before release.
4. Reproduce with the provider in isolation to identify the specific attribute, then report/fix in the provider.

Example fix

null

// Go (provider): validate scalar schema types are primitive before read
for name, s := range resource.Schema {
    if isPrimitiveRead(s) {
        switch s.Type {
        case schema.TypeString, schema.TypeBool, schema.TypeInt, schema.TypeFloat:
        default:
            return fmt.Errorf("field %q routed to primitive reader has non-scalar Type %d", name, s.Type)
        }
    }
}

// Go: confirm a Type is a primitive scalar
func isScalarType(t schema.ValueType) bool {
    switch t { case schema.TypeString, schema.TypeBool, schema.TypeInt, schema.TypeFloat: return true }
    return false
}

When it happens

Trigger: Terraform reads a primitive field value through the legacy map field reader for a schema attribute whose `Type` is a collection/invalid type rather than a scalar, or whose Type is unset. The reader dispatches scalars to readPrimitive and the bad type falls into the default panic.

Common situations: Provider schema with a field declared as a primitive in one place but a collection elsewhere; TypeInvalid from an unset Type; mismatched schema across SDK versions; reading state/config via legacy paths for a field the schema no longer describes as scalar.

Related errors

• Unknown type: %s
• Unknown type: %#v
• Unknown type: %s
• invalid Schema.Type %s
• unknown type: %#v

AI-assisted analysis of hashicorp/terraform@c9def3e214 (2026-08-07). Data as JSON: /api/errors/a60aca00835d7037. Report an issue: GitHub.