format static method

List<String> format(String source, List<ParserErrorMessage> messages, { int lineLimit = 80, int offset = 0, String title = 'Format exception', })

Returns formatted error as strings.

Parameters: String source Text of source code.

List<ParserErrorMessage> error List of parser error messages.

int lineLimit Length limit of the formatted line.

int offset Offset to be added to the values "start" and "end".

String title Title of parser error

Implementation

static List<String> format(String source, List<ParserErrorMessage> messages,
    {int lineLimit = 80, int offset = 0, String title = 'Format exception'}) {
  if (lineLimit < 1) {
    throw ArgumentError.value(lineLimit, 'lineLimit');
  }

  if (offset < 0) {
    throw ArgumentError.value(offset, 'offset');
  }

  final result = <String>[];
  final text = Text(source);
  final sourceLength = source.length;
  for (var error in messages) {
    var position = error.end + offset;
    if (error.start != error.end) {
      position = error.start + offset;
    }

    Location? location;
    Line? line;
    var locationString = '';
    if (position < sourceLength) {
      line = text.lineAt(position);
      location = text.locationAt(position);
      locationString = ' (${location.toString()})';
    }

    result.add('$title$locationString: ${error.message}');
    if (line != null) {
      var string = String.fromCharCodes(line.characters);
      string = string.replaceAll('\n', '');
      string = string.replaceAll('\r', '');
      var indicatorLength = 1;
      var indicatorPosition = 0;
      if (location != null) {
        indicatorPosition = location.column - 1;
      }
      if (error.end != error.start) {
        indicatorLength = error.end - error.start;
      }

      if (indicatorLength > lineLimit) {
        indicatorLength = lineLimit;
      }

      if (indicatorPosition + indicatorLength > lineLimit) {
        if (indicatorPosition < lineLimit || indicatorLength < lineLimit) {
          final delta = (indicatorPosition + indicatorLength) - lineLimit;
          string = string.substring(delta);
          indicatorPosition -= delta;
        } else {
          string = string.substring(indicatorPosition);
          indicatorPosition = 0;
        }
      }

      if (string.length > lineLimit) {
        string = string.substring(0, lineLimit);
      }

      final prefix = ''.padRight(indicatorPosition, ' ');
      final suffix = ''.padRight(indicatorLength, '^');
      final indicator = '$prefix$suffix';
      result.add(string);
      result.add(indicator);
    }
  }

  return result;
}