Null check missing in code: Line chart with hidden labels throws exception

[PT10]

Bug description

There is a clear issue in the code. When "isVisibleInLegend" is false, null is returned. And then there is no null check in the caller.

chart_series.dart

  @override
  List<LegendItem>? buildLegendItems(int index) {
    final List<LegendItem>? items = super.buildLegendItems(index);
    if (trendlineContainer != null) {
      items!.addAll(trendlineContainer!.buildLegendItems(index, this)!);
    }
    return items;
  }

Here a null check is required on items before calling items!.addAll.

Following is the method from base class which this code calls (super.buildLegendItems) and it can return null.

  @override
  List<LegendItem>? buildLegendItems(int index) {
    if (isVisibleInLegend) {
      final LegendItem legendItem = ChartLegendItem(
        text: legendItemText ?? name,
        iconType: toLegendShapeMarkerType(legendIconType, this),
        iconColor: legendIconColor(),
        iconBorderColor: legendIconBorderColor(),
        iconBorderWidth: legendIconBorderWidth(),
        series: this,
        seriesIndex: index,
        pointIndex: 0,
        isToggled: _isToggled(),
        shader: legendIconShader(),
        overlayMarkerType: markerSettings.isVisible
            ? toShapeMarkerType(markerSettings.shape)
            : null,
        imageProvider: legendIconType == LegendIconType.image
            ? parent?.legend?.image
            : null,
        onTap: handleLegendItemTapped,
        onRender: _handleLegendItemCreated,
      );
      return <LegendItem>[legendItem];
    } else {
      return null;
    }
  }

Steps to reproduce

Any line chart which a single series and show legend flag on.

Code sample

Code sample

chart_series.dart

@OverRide
List? buildLegendItems(int index) {
final List? items = super.buildLegendItems(index);
if (trendlineContainer != null) {
items!.addAll(trendlineContainer!.buildLegendItems(index, this)!);
}
return items;
}

Here a null check is required on items before calling items!.addAll.


Following is the method from base class which this code calls (super.buildLegendItems) and it can return null.

@OverRide
List? buildLegendItems(int index) {
if (isVisibleInLegend) {
final LegendItem legendItem = ChartLegendItem(
text: legendItemText ?? name,
iconType: toLegendShapeMarkerType(legendIconType, this),
iconColor: legendIconColor(),
iconBorderColor: legendIconBorderColor(),
iconBorderWidth: legendIconBorderWidth(),
series: this,
seriesIndex: index,
pointIndex: 0,
isToggled: _isToggled(),
shader: legendIconShader(),
overlayMarkerType: markerSettings.isVisible
? toShapeMarkerType(markerSettings.shape)
: null,
imageProvider: legendIconType == LegendIconType.image
? parent?.legend?.image
: null,
onTap: handleLegendItemTapped,
onRender: _handleLegendItemCreated,
);
return [legendItem];
} else {
return null;
}
}

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Stack Traces

Stack Traces

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On which target platforms have you observed this bug?

Web

Flutter Doctor output

Doctor output

Doctor summary (to see all details, run flutter doctor -v):
[✓] Flutter (Channel stable, 3.24.1, on macOS 14.3.1 23D60 darwin-arm64, locale en-IN)
[!] Android toolchain - develop for Android devices (Android SDK version 34.0.0)
    ✗ cmdline-tools component is missing
      Run `path/to/sdkmanager --install "cmdline-tools;latest"`
      See https://developer.android.com/studio/command-line for more details.
    ✗ Android license status unknown.
      Run `flutter doctor --android-licenses` to accept the SDK licenses.
      See https://flutter.dev/to/macos-android-setup for more details.
[✓] Xcode - develop for iOS and macOS (Xcode 15.3)
[✓] Chrome - develop for the web
[✓] Android Studio (version 2023.2)
[✓] VS Code (version 1.86.2)
[✓] Connected device (3 available)
[✓] Network resources

! Doctor found issues in 1 category.