format function Null safety

String format(
  1. String input,
  2. {List<String>? args,
  3. Map<String, String>? replace,
  4. VariableStyle? style,
  5. VariableResolver? resolver}
)

Implementation

String format(String input,
    {List<String>? args,
    Map<String, String>? replace,
    VariableStyle? style,
    VariableResolver? resolver}) {
  style ??= VariableStyle.DEFAULT;

  if (Zone.current['console.format.variable_style'] != null) {
    style = Zone.current['console.format.variable_style'];
  }

  var out = input;
  var allKeys = style!.findVariables(input);

  for (var id in allKeys) {
    if (args != null) {
      try {
        var index = int.parse(id);
        if (index < 0 || index > args.length - 1) {
          throw RangeError.range(index, 0, args.length - 1);
        }
        out = style.replace(out, '${index}', args[index]);
        continue;
        // ignore: empty_catches
      } on FormatException {}
    }

    if (replace != null && replace.containsKey(id)) {
      out = style.replace(out, id, replace[id]!);
      continue;
    }

    if (id.startsWith('@') || id.startsWith('color.')) {
      var color = id.startsWith('@') ? id.substring(1) : id.substring(6);
      if (color.isEmpty) {
        throw Exception('color directive requires an argument');
      }

      if (_COLORS.containsKey(color)) {
        out = style.replace(out, '${id}', _COLORS[color].toString());
        continue;
      }

      if (color == 'normal' || color == 'end') {
        out = style.replace(out, id, '${Console.ANSI_ESCAPE}0m');
        continue;
      }
    }

    if (id.startsWith('env.')) {
      var envVariable = id.substring(4);
      if (envVariable.isEmpty) {
        throw Exception('Unknown Key: ${id}');
      }
      var value = Platform.environment[envVariable];
      value ??= '';
      out = style.replace(out, id, value);
      continue;
    }

    if (id.startsWith('platform.')) {
      var variable = id.substring(9);

      if (variable.isEmpty) {
        throw Exception('Unknown Key: ${id}');
      }

      var value = _resolvePlatformVariable(variable);

      out = style.replace(out, id, value);
      continue;
    }

    if (resolver != null) {
      var value = resolver(id);
      out = style.replace(out, id, value);
    } else {
      throw Exception('Unknown Key: ${id}');
    }
  }

  return out;
}