fix: iterable equality comparisons

[felangel]

Status

READY

Breaking Changes

NO

Description

• fix: iterable equality comparisons (closes Equatable doesn't work with nested custom Iterable objects #101)

Todos

• Tests
• Documentation
• Examples

[nxtSwitch]

Hi @felangel
Thanks for the prompt solution of the problem!

Can you please tell me if there is a way to solve this problem for manually overriding the ==? Thanks!

[felangel]

Hi @nxtSwitch 👋

Can you provide a bit more context or a reproduction sample? I'm not sure I understand the use-case/question.

[nxtSwitch]

А similar case, but without using the equatable:

class SimpleEquatable<T> extends Equatable {
  const SimpleEquatable(this.data);

  final T data;

  @override
  List<Object> get props => [data];
}

@immutable
class IterableWithFlag extends Iterable<String> {
  final bool flag;
  final List<String> list;

  const IterableWithFlag({this.list, this.flag});

  @override
  bool operator ==(Object other) {
    return identical(this, other) ||
        other is IterableWithFlag && flag == other.flag;
  }

  @override
  Iterator<String> get iterator => list.iterator;
}

  const instanceA = IterableWithFlag(list: ['1', '2'], flag: true);
  const instanceB = IterableWithFlag(list: ['1', '2'], flag: false);

  print(const SimpleEquatable(instanceA) == const SimpleEquatable(instanceB)); // true

[felangel]

@nxtSwitch I believe the reason why that isn't working is because two Iterable instances are considered equal if they have the same elements in the same order. I wouldn't recommend having a custom Iterable with a flag. Instead it would be good to decouple the two:

@immutable
class Iterable extends Iterable<String> {
  final List<String> list;

  const IterableWithFlag({this.list});

  @override
  Iterator<String> get iterator => list.iterator;
}

class FlagWrapper<T> {
  final T data;
  final bool flag;

  const FlagWrapper({this.data, this.flag});

  @override
  bool operator ==(Object other) {
    return identical(this, other) ||
        other is FlagWrapper<T> && flag == other.flag && data == other.data;
  }
}

Hope that helps 👍

[Tokenyet]

I might make an issue, but It's maked as fixed, so I can't sure It's my problem or not. I have a test that used equatable but failed on nested iterable.

Logs:

   Which: at location [0] is ConsoleLine:<ConsoleLine((ConsoleText(null, null, false, 2022-03-01 16:08:51,840 main WARN Advanced terminal features are not available in this environment)))> instead of ConsoleLine:<ConsoleLine([ConsoleText(null, null, false, 2022-03-01 16:08:51,840 main WARN Advanced terminal features are not available in this environment)])>

The related classes:

class ConsoleLine extends Equatable {
  final Iterable<ConsoleText> texts;
  const ConsoleLine({
    required this.texts,
  });

  ConsoleLine copyWith({
    Iterable<ConsoleText>? texts,
  }) {
    return ConsoleLine(
      texts: texts ?? this.texts,
    );
  }

  @override
  List<Object> get props => [texts];
}

class ConsoleText extends Equatable {
  final Color? foreground;
  final Color? background;
  final bool bold;
  final String text;
  const ConsoleText({
    this.foreground,
    this.background,
    this.bold = false,
    required this.text,
  });

  @override
  List<Object?> get props => [foreground, background, bold, text];

  ConsoleText copyWith({
    Color? foreground,
    Color? background,
    bool? bold,
    String? text,
  }) {
    return ConsoleText(
      foreground: foreground ?? this.foreground,
      background: background ?? this.background,
      bold: bold ?? this.bold,
      text: text ?? this.text,
    );
  }
}

The generator method

  Iterable<ConsoleLine> parse(String text) sync* {
    final lines = const LineSplitter().convert(text);
    if (lines.isEmpty) return;
    for (final line in lines) {
      final parseResults = decodeAnsiColorEscapeCodes(line, _ansiUp);
      yield ConsoleLine(
        texts: parseResults.map(
          (e) => ConsoleText(
            bold: e.bold,
            text: e.text,
            foreground: _colorFromAnsi(e.fgColor),
            background: _colorFromAnsi(e.bgColor),
          ),
        ),
      );
    }
  }

If I change the generator method to the following, the test passed...

  Iterable<ConsoleLine> parse(String text) sync* {
    final lines = const LineSplitter().convert(text);
    if (lines.isEmpty) return;
    for (final line in lines) {
      final parseResults = decodeAnsiColorEscapeCodes(line, _ansiUp);
      yield ConsoleLine(
        texts: parseResults.map(
          (e) => ConsoleText(
            bold: e.bold,
            text: e.text,
            foreground: _colorFromAnsi(e.fgColor),
            background: _colorFromAnsi(e.bgColor),
          ),
        ).toList(),
      );
    }
  }

Or make the List<Object> get props => [texts]; to List<Object> get props => [...texts];, also pass the test.

Any help would be appreciated!

Edit:
Not sure what's the best way to handle this case in tests, but I change the form from

        expect(
          consoleRepository.parse(rawA),
          [
            ConsoleLine(
              texts: [
                const ConsoleText(
                    text:
                        '2022-03-01 16:08:51,840 main WARN Advanced terminal features are not available in this environment'),
              ],
            ),
          ],
        );

to

        expect(
          consoleRepository.parse(rawA),
          [
            ConsoleLine(
              texts: Iterable.castFrom([
                const ConsoleText(
                    text:
                        '2022-03-01 16:08:51,840 main WARN Advanced terminal features are not available in this environment'),
              ]),
            ),
          ],
        );

For whom stuck on nested iterable, I think here is the solution, might not be the best.

[felangel]

@Tokenyet Equatable should support nested iterable props. I added more tests for this specific case in #135. Are you able to provide a unit test that fails to illustrate the problem you're facing? Thanks!