defaultStackFilter static method

Iterable<String> defaultStackFilter(
  1. Iterable<String> frames
)

Converts a stack to a string that is more readable by omitting stack frames that correspond to Dart internals.

This is the default filter used by dumpErrorToConsole if the FlutterErrorDetails object has no FlutterErrorDetails.stackFilter callback.

This function expects its input to be in the format used by StackTrace.toString(). The output of this function is similar to that format but the frame numbers will not be consecutive (frames are elided) and the final line may be prose rather than a stack frame.

Implementation

static Iterable<String> defaultStackFilter(Iterable<String> frames) {
  final removedPackagesAndClasses = <String, int>{
    'dart:async-patch': 0,
    'dart:async': 0,
    'package:stack_trace': 0,
    'class _AssertionError': 0,
    'class _FakeAsync': 0,
    'class _FrameCallbackEntry': 0,
    'class _Timer': 0,
    'class _RawReceivePortImpl': 0,
  };
  var skipped = 0;

  final List<StackFrame> parsedFrames = StackFrame.fromStackString(frames.join('\n'));

  for (var index = 0; index < parsedFrames.length; index += 1) {
    final StackFrame frame = parsedFrames[index];
    final className = 'class ${frame.className}';
    final package = '${frame.packageScheme}:${frame.package}';
    if (removedPackagesAndClasses.containsKey(className)) {
      skipped += 1;
      removedPackagesAndClasses.update(className, (int value) => value + 1);
      parsedFrames.removeAt(index);
      index -= 1;
    } else if (removedPackagesAndClasses.containsKey(package)) {
      skipped += 1;
      removedPackagesAndClasses.update(package, (int value) => value + 1);
      parsedFrames.removeAt(index);
      index -= 1;
    }
  }
  final reasons = List<String?>.filled(parsedFrames.length, null);
  for (final StackFilter filter in _stackFilters) {
    filter.filter(parsedFrames, reasons);
  }

  final result = <String>[];

  // Collapse duplicated reasons.
  for (var index = 0; index < parsedFrames.length; index += 1) {
    final start = index;
    while (index < reasons.length - 1 &&
        reasons[index] != null &&
        reasons[index + 1] == reasons[index]) {
      index++;
    }
    var suffix = '';
    if (reasons[index] != null) {
      if (index != start) {
        suffix = ' (${index - start + 2} frames)';
      } else {
        suffix = ' (1 frame)';
      }
    }
    final resultLine = '${reasons[index] ?? parsedFrames[index].source}$suffix';
    result.add(resultLine);
  }

  // Only include packages we actually elided from.
  final where = <String>[
    for (final MapEntry<String, int> entry in removedPackagesAndClasses.entries)
      if (entry.value > 0) entry.key,
  ]..sort();
  if (skipped == 1) {
    result.add('(elided one frame from ${where.single})');
  } else if (skipped > 1) {
    if (where.length > 1) {
      where[where.length - 1] = 'and ${where.last}';
    }
    if (where.length > 2) {
      result.add('(elided $skipped frames from ${where.join(", ")})');
    } else {
      result.add('(elided $skipped frames from ${where.join(" ")})');
    }
  }
  return result;
}