hashicorp/terraform · critical

Unknown kind: %s

Error message

Unknown kind: %s

What it means

Panics in ResourceConfig.get (resource.go:410) while walking a dotted key path through raw config via reflection. The switch handles only Map, Slice, and String kinds; any other reflect.Kind (struct, int, bool, pointer) in the raw config tree panics.

Source

Thrown at internal/legacy/terraform/resource.go:410

					return nil, false
				}
				if int(i) < 0 || int(i) >= cv.Len() {
					return nil, false
				}
				current = cv.Index(int(i)).Interface()
			}
		case reflect.String:
			// This happens when map keys contain "." and have a common
			// prefix so were split as path components above.
			actualKey := strings.Join(parts[i-1:], ".")
			if prevMap, ok := previous.(map[string]interface{}); ok {
				v, ok := prevMap[actualKey]
				return v, ok
			}

			return nil, false
		default:
			panic(fmt.Sprintf("Unknown kind: %s", cv.Kind()))
		}
	}

	return current, true
}

// unknownCheckWalker
type unknownCheckWalker struct {
	Unknown bool
}

func (w *unknownCheckWalker) Primitive(v reflect.Value) error {
	if v.Interface() == hcl2shim.UnknownVariableValue {
		w.Unknown = true
	}

	return nil
}

View on GitHub (pinned to c9def3e214)

Solutions

1. Ensure raw config values are only map[string]interface{}, []interface{}, or string.
2. Build raw values via hcl2shim rather than hand-constructing native Go structs.
3. Never inject pointers or structs into ResourceConfig.Raw/Config.

Example fix

// before
cfg.Raw = map[string]interface{}{"x": MyStruct{...}}
// after
cfg.Raw = map[string]interface{}{"x": map[string]interface{}{"a": "1"}}

func rawConfigWalkable(raw interface{}) error {
    switch v := raw.(type) {
    case map[string]interface{}:
        for _, c := range v { if err := rawConfigWalkable(c); err != nil { return err } }
    case []interface{}:
        for _, c := range v { if err := rawConfigWalkable(c); err != nil { return err } }
    case string, nil:
    default:
        return fmt.Errorf("unsupported raw kind %T in config", raw)
    }
    return nil
}

func isWalkableKind(raw interface{}) bool {
    switch raw.(type) {
    case map[string]interface{}, []interface{}, string, nil: return true
    }
    return false
}

When it happens

Trigger: Calling ResourceConfig.Get(k) where the raw config value at some path component is a Go struct, primitive (bool/int), or pointer — i.e. raw config not in the map/slice/string shape normally produced by hcl2shim.

Common situations: Custom code injecting non-standard Go values into ResourceConfig.Raw, schema/config corruption, or test fixtures using wrong Go types.

Related errors

• missing field in set: %s.%s
• set item just set doesn't exist
• invalid index value %q
• argument %q is required
• invalid value for %q: %s

AI-assisted analysis of hashicorp/terraform@c9def3e214 (2026-08-07). Data as JSON: /api/errors/c96fb411a2ef9058. Report an issue: GitHub.