Add svg finder

[SimonWeidemann]

This pull request adds a test helper to find svgs in widget tests.
The implementation is similar to the default find.image function.

[dnfield]

This has to get moved to another package. We can't have the runtime depending on flutter_test.

[SimonWeidemann]

Sorry for the late response.
I see what you mean.
How should we go further?
Should I create a separate repository or should we integrate the package in this one?
For example like this:

flutter_svg
│ 
├──.github
├──.gitignore
├──READMED.md
├──LICENSE
├──......
└─packages
       │ 
       ├── flutter_svg
       │         ├── example
       │         ├── lib
       │         ├── test
       │         ├── README.md
       │         ├── ....
       │         └── pubspec.yaml
       │ 
       └── flutter_svg_test
                   ├── example
                   ├── lib
                   ├── test
                   ├── README.md
                   ├── ....
                   └── pubspec.yaml

I am willing to make this work, but you probably need to guide me a bit.

I can add some more finder like the following one, so the package is not that small.

/// Finds widgets created by [SvgPicture.asset] with the [path] argument.
///
/// ## Sample code
/// ```dart
/// expect(svgAssetWithPath('assets/asset_name.svg'), findsOneWidget);
/// ```
/// This will match one [SvgPicture.asset] with the [path] 'assets/asset_name.svg'.
///
/// If the `skipOffstage` argument is true (the default), then this skips
/// nodes that are [Offstage] or that are from inactive [Route]s.
Finder svgAssetWithPath(String path, {bool skipOffstage = true}) {
  return _SvgAssetWithPathFinder(svgPath: path, skipOffstage: skipOffstage);
}

class _SvgAssetWithPathFinder extends MatchFinder {
  _SvgAssetWithPathFinder({required String svgPath, super.skipOffstage})
      : _svgPath = svgPath;

  final String _svgPath;

  @override
  String get description => "Path: '$_svgPath' and created by SvgPicture.asset";

  @override
  bool matches(Element candidate) {
    var result = false;
    final widget = candidate.widget;
    if (widget is SvgPicture) {
      final bytesLoader = widget.bytesLoader;
      if (bytesLoader is SvgAssetLoader) {
        result = bytesLoader.assetName == _svgPath;
      }
    }
    return result;
  }
}

[dnfield]

Yes, this needs to be its own package, which the repo isn't currently structured well for. I think your proposed structure is fine.

[dnfield]

Please update this file with a description of what this package is and how to use it.

[dnfield]

I think this should be removed?

[dnfield]

I don't think this file is necessary

[dnfield]

I think this is duplicated from the other package and isn't referred to anywhere, can it be removed?

[SimonWeidemann]

I use this file in two SvgFileLoader tests.

[dnfield]

This looks close. It'll need a conflict resolution. Thanks!

[SimonWeidemann]

I worked through the review comments.
Now the repository has a readme and also each package .
I thought this would be more suitable.

[dnfield]

So looking at this, it surprises me that we're not just passing in the SvgPicture, i.e. find.svg(asset).

Sorry I didn't see this until now. This is looking pretty close though.

[SimonWeidemann]

If I adjust the finder accordingly:

        Finder svg(SvgPicture svg, {bool skipOffstage = true}) {
           return _SvgFinder(svg, skipOffstage: skipOffstage);
         }

      class _SvgFinder extends MatchFinder {
        _SvgFinder(this._svg, {super.skipOffstage});
      
         final SvgPicture _svg;
      
         @override
         String get description => "svg: '$_svg'";
      
         @override
         bool matches(Element candidate) {
           return candidate.widget == _svg;
         }
       }

For me the following test should pass:

      testWidgets('asset svg', (WidgetTester widgetTester) async {
        final SvgPicture asset = SvgPicture.asset( 'test/flutter_logo.svg');
        final SvgPicture asset2 = SvgPicture.asset('test/flutter_logo.svg');
        await widgetTester.pumpWidget(asset);
        expect(find.svg(asset2), findsOneWidget);
      });

But unfortunately the test does not pass, because the equals method compares the object not the fields.
If I do this by hand my finder would look like this:

        Finder svg(SvgPicture svg, {bool skipOffstage = true}) {
           return _SvgFinder(svg, skipOffstage: skipOffstage);
         }

      class _SvgFinder extends MatchFinder {
        _SvgFinder(this._svg, {super.skipOffstage});
      
         final SvgPicture _svg;
      
         @override
         String get description => "svg: '$_svg'";
      
         @override
         bool matches(Element candidate) {
           return  widget is SvgPicture &&
                      _svg.runtimeType == widget.runtimeType &&
                     _svg.width == widget.width &&
                     _svg.height == widget.height &&
                     _svg.fit == widget.fit &&
                     _svg.alignment == widget.alignment &&
                     _svg.bytesLoader == widget.bytesLoader &&
                     _svg.placeholderBuilder == widget.placeholderBuilder &&
                     _svg.matchTextDirection == widget.matchTextDirection &&
                     _svg.allowDrawingOutsideViewBox == widget.allowDrawingOutsideViewBox &&
                     _svg.semanticsLabel == widget.semanticsLabel &&
                     _svg.excludeFromSemantics == widget.excludeFromSemantics &&
                     _svg.clipBehavior == widget.clipBehavior &&
                     _svg.colorFilter == widget.colorFilter &&
                     _svg.theme == widget.theme;
         }
       }

While writing the test helper I orientated on the find.text and find.image methods from the flutter library.
In both they compare just with a subset of the fields. In find.text with the string and infind.image
with the image provider.
I think this was done because otherwise you would have to declare all fields in the test.
Sometimes it is just needed to locate a widget and afterwards compare different aspects, with expect.
Also sometimes it would be really hard to compare objects during an animation, where for example the double value has a huge amount of decimal place.

I would go with the current implementation.

Thanks for the two commits!

[dnfield]

Ahh interesting. I would have assumed the impelementation would be something like return widget is SvgPicture && _svg.bytesLoader = widget.bytesLoader, but perhaps this makes more sense. If that's how this works for Image though I think it makes sense.

[dnfield]

Note to self: rolling this into google is going to require updates to the copy scripts