nektos/act · error

'%s' in map key not implemented

Error message

'%s' in map key not implemented

What it means

Same code path as the map-key error at pkg/exprparser/interpreter.go:295: property lookup iterates a map with MapRange and rejects any key whose reflect.Kind is not String, embedding the kind name in the message. It guards the dot-notation (.foo) accessor only.

Source

Thrown at pkg/exprparser/interpreter.go:295

			}
			return string(text), nil
		}
		return i, nil

	case reflect.Map:
		iter := left.MapRange()

		for iter.Next() {
			key := iter.Key()

			switch key.Kind() {
			case reflect.String:
				if strings.EqualFold(key.String(), property) {
					return impl.getMapValue(iter.Value())
				}

			default:
				return nil, fmt.Errorf("'%s' in map key not implemented", key.Kind())
			}
		}

		return nil, nil

	case reflect.Slice:
		var values []interface{}

		for i := 0; i < left.Len(); i++ {
			value, err := impl.getPropertyValue(left.Index(i).Elem(), property)
			if err != nil {
				return nil, err
			}

			values = append(values, value)
		}

		return values, nil

View on GitHub (pinned to 4f41128141)

Solutions

1. Switch to bracket access with a string index for such keys.
2. Normalize maps to string keys before they enter expressions.
3. Restructure source data to use string keys or arrays.

Example fix

# go embedding
// before
env.Vars = map[int]string{1: 'a'}
// after
env.Vars = map[string]string{'1': 'a'}

func normalizeMapKeys(v interface{}) interface{} {
  switch t := v.(type) {
  case map[interface{}]interface{}:
    out := map[string]interface{}{}
    for k, val := range t { out[fmt.Sprintf('%v', k)] = normalizeMapKeys(val) }
    return out
  case map[string]interface{}:
    for k, val := range t { t[k] = normalizeMapKeys(val) }
  }
  return v
}

When it happens

Trigger: Evaluating x.prop where x is a map[interface{}]interface{} or map[int]string; JSON decoded with number keys under act's untyped unmarshaling; composite-action inputs building non-string keyed maps.

Common situations: Dot access on fromJSON results with non-string keys; env data injected by custom embedding code; YAML !!int keys flowing into the expression environment.

Related errors

• Unavailable context: %s
• Cannot parse non-string type %v as JSON
• Invalid JSON: %v
• The following format string is invalid: '%s'
• The following format string references more arguments than w

AI-assisted analysis of nektos/act@4f41128141 (2026-08-15). Data as JSON: /api/errors/b10f1d2c4ad453f7. Report an issue: GitHub.