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avoid-nullable-interpolation

added in: 1.8.0
warning
⚙️
Pro+
preset: recommended

Warns when an interpolation string contains a nullable value.

Using nullable values in interpolations can lead to unexpected output. Consider checking the value to be non-null before using it in the interpolation.

⚙️ Config​

Set ignored-invocations (default is empty) to ignore interpolation strings within specific invocations (example).

analysis_options.yaml
dart_code_metrics:
  rules:
    - avoid-nullable-interpolation:
        ignored-invocations:
          - log
          - debugPrint

Example​

❌ Bad:

void function(String? value) {
  print('$value hello'); // LINT: This interpolation is potentially nullable. Try checking for a null value first.
}

✅ Good:

void function(String? value) {
  if (value != null) {
    print('$value hello'); // Correct, checked for not null first
  }

  print('${value != null ? value : ''} hello');
}

Example with "ignored-invocations"​

Config
analysis_options.yaml
dart_code_metrics:
  rules:
    - avoid-nullable-interpolation:
        ignored-invocations:
          - debugPrint
void function(String? value) {
  debugPrint('output: $value'); // Correct, 'debugPrint' is ignored
}