[Bug report] extract method: The argument type 'void Function(SnackBarData)' can't be assigned to the parameter type 'void Function(dynamic)'

[stephane-archer]

Input:

        var snackBarData = await _executeConversionWithExceptionAsValue(
          () async {
            await JxlToJpeg.convert(
              jxlFile,
              outputPath: path_lib.join(
                selectedOutputDirPath,
                path_lib.setExtension(path_lib.basename(jxlFile.path), '.jpg'),
              ),
            );
          },
        );
        if (snackBarData != null) {
          displayFeedbackForTheUser(snackBarData);
        }
        _progress.value += 1;

extract method _abc

Result:

  Future<void> _abc(File jxlFile, String selectedOutputDirPath, void displayFeedbackForTheUser(SnackBarData )) async {
    var snackBarData = await _executeConversionWithExceptionAsValue(
      () async {
        await JxlToJpeg.convert(
          jxlFile,
          outputPath: path_lib.join(
            selectedOutputDirPath,
            path_lib.setExtension(path_lib.basename(jxlFile.path), '.jpg'),
          ),
        );
      },
    );
    if (snackBarData != null) {
      displayFeedbackForTheUser(snackBarData);
    }
    _progress.value += 1;
  }

The argument type 'void Function(SnackBarData)' can't be assigned to the parameter type 'void Function(dynamic)'.

Correct output:

  Future<void> _abc(File jxlFile, String selectedOutputDirPath, void Function(SnackBarData) displayFeedbackForTheUser) async {
    var snackBarData = await _executeConversionWithExceptionAsValue(
      () async {
        await JxlToJpeg.convert(
          jxlFile,
          outputPath: path_lib.join(
            selectedOutputDirPath,
            path_lib.setExtension(path_lib.basename(jxlFile.path), '.jpg'),
          ),
        );
      },
    );
    if (snackBarData != null) {
      displayFeedbackForTheUser(snackBarData);
    }
    _progress.value += 1;
  }

[DanTup]

Are you able to provide a complete code sample I can use to repro this? I tried stubbing out the things missing from your code, but I wasn't able to reproduce the issue:

Future<void> main() async {
  var jxlFile = 1;
  var value = 1;
  var selectedOutputDirPath = '';
  var snackBarData = await _executeConversionWithExceptionAsValue(
    () async {
      await JxlToJpeg.convert(
        jxlFile,
        outputPath: join(
          selectedOutputDirPath,
          '.jpg',
        ),
      );
    },
  );
  if (snackBarData != null) {
    displayFeedbackForTheUser(snackBarData);
  }
  value += 1;
}

Future<Object?> _executeConversionWithExceptionAsValue(Function f) =>
    throw UnimplementedError();

Future<void> foo() async {}

Future<Object?> bar(Function x) async {}

class JxlToJpeg {
  static Future<void> convert(int a, {required String outputPath}) {
    throw UnimplementedError();
  }
}

String join(String a, String b) => throw UnimplementedError();

void displayFeedbackForTheUser(Object? o) {}

Extracting the same code from here didn't produce any incorrect code.

Thanks!

[stephane-archer]

  Future<void> _processDroppedFiles(DropDoneDetails dropDoneDetails) async {
    var displayFeedbackForTheUser = getDisplayFeedbackForTheUser(context);
    if (_appState.value != _AppState.idle) {
      return;
    }
    final filePaths = _getDroppedPath(dropDoneDetails);
    if (filePaths.isEmpty) {
      return;
    }
    _appState.value = _AppState.selecting;
    String? selectedOutputDirPath = await FilePicker.platform.getDirectoryPath(
      lockParentWindow: true,
      dialogTitle: "Please select an output folder",
      initialDirectory: path_lib.dirname(filePaths.first),
    );
    if (selectedOutputDirPath == null) {
      _appState.value = _AppState.idle;
      return;
    }
    try {
      _appState.value = _AppState.processing;
      final jpegFiles = _pathsToFiles(_getJpegPaths(filePaths));
      final jxlFiles = _pathsToFiles(_getJxlPaths(filePaths));
      _batchSize.value = jpegFiles.length + jxlFiles.length;
      _progress.value = 0;
      for (var jpegFile in jpegFiles) {
        var snackBarData = await _executeConversionWithExceptionAsValue(
          () async {
            await JpegToJxl.convert(
              jpegFile,
              outputPath: path_lib.join(
                selectedOutputDirPath,
                path_lib.setExtension(path_lib.basename(jpegFile.path), '.jxl'),
              ),
            );
          },
        );
        if (snackBarData != null) {
          displayFeedbackForTheUser(snackBarData);
        }
        _progress.value += 1;
      }
      for (var jxlFile in jxlFiles) {
        var snackBarData = await _executeConversionWithExceptionAsValue(
          () async {
            await JxlToJpeg.convert(
              jxlFile,
              outputPath: path_lib.join(
                selectedOutputDirPath,
                path_lib.setExtension(path_lib.basename(jxlFile.path), '.jpg'),
              ),
            );
          },
        );
        if (snackBarData != null) {
          displayFeedbackForTheUser(snackBarData);
        }
        _progress.value += 1;
      }
    } finally {
      displayFeedbackForTheUser((message: 'Done', color: Colors.green));
      _appState.value = _AppState.idle;
    }
  }

with this code in another file:

import 'package:flutter/material.dart';

void Function(SnackBarData) getDisplayFeedbackForTheUser(BuildContext context) {
  return (snackBarData) {
    final snackBar = SnackBar(
      backgroundColor: snackBarData.color,
      content: Text(snackBarData.message),
      duration: snackBarData.color != Colors.green
          ? Duration(seconds: 6)
          : Duration(seconds: 4),
    );
    ScaffoldMessenger.of(context).showSnackBar(snackBar);
  };
}

typedef SnackBarData = ({String message, Color color});

sorry my code is pretty ugly, I hope this helps you solve the issue, make sure to use a typedef, I think this is what cause the issue

[DanTup]

Thanks! I was able to trim this down to:

Future<void> f(void Function(String) f, String a) async {
  f(a);
}

The issue here is that the refactor was written before the generic function syntax (where function types can have parameters with no names) and writes a signature using the old style (which doesn't support not having names).

[DanTup]

Got a fix up for review at https://dart-review.googlesource.com/c/sdk/+/397900

The fix is in the Dart analysis server so once merged, will ship in a future Dart/Flutter SDK release (not a VS Code extension release).

[stephane-archer]

@DanTup you are the best! thank you for solving my issue!

[DanTup]

Thanks, no problem! The fix has now landed in the Dart SDK and will be included in a future Dart/Flutter SDK release.