anchor.diff:  
     // Formatting change in 2.9 with hashbang first line
     if (dartVersion >= Version(2, 9, 0, pre: '0')) {
  -    await shell.run('''
  +    try {
  +      var dirs = await topLevelDir(path);
  +      await shell.run('''
         # Formatting
  -      dartfmt -n --set-exit-if-changed .
  +      dartfmt -n --set-exit-if-changed ${filterDartDirs(dirs).join(' ')}
       ''');
  +    } catch (e) {
  +      // Sometimes we allow formatting errors...
  +
  +      // if (supportsNnbdExperiment) {
  +      //  stderr.writeln('Error in dartfmt during nnbd experiment, ok...');
  +      //} else {
  +      //
  +
  +      // but in general no!
  +      rethrow;
  +    }
     }
   
     if (isFlutterPackage) {
  
positive.code:     }
    }
  }
  
negative.code:   var isFlutterPackage = pubspecYamlSupportsFlutter(pubspecMap);
  
    var sdkBoundaries = pubspecYamlGetSdkBoundaries(pubspecMap);
    var supportsNnbdExperiment =
        analysisOptionsSupportsNnbdExperiment(analysisOptionsMap);
  
    if (!sdkBoundaries.match(dartVersion)) {
      stderr.writeln('Unsupported sdk boundaries for dart $dartVersion');
      return;
  