parseDotEnv function

Map<String, String> parseDotEnv(
  1. String text
)

Parses dotenv assignments into strings without interpolation or evaluation.

Supports blank lines, comments, export, empty values, literal single quotes, and double quotes with \n, \r, \t, \\, and \" escapes. Unquoted inline comments require whitespace before #. Quoted values must fit on one line; trailing content must be a comment. Duplicate keys use the last assignment. Keys match [A-Za-z_][A-Za-z0-9_]* and are case-sensitive.

Implementation

Map<String, String> parseDotEnv(String text) {
  final values = <String, String>{};
  final lines = text.replaceFirst(RegExp(r'^\uFEFF'), '').split('\n');
  for (var index = 0; index < lines.length; index++) {
    var line = lines[index].trim();
    if (line.isEmpty || line.startsWith('#')) continue;
    if (line.startsWith('export ')) line = line.substring(7).trimLeft();
    final equals = line.indexOf('=');
    Never invalid() => throw ConfigParseException(
        'Invalid dotenv syntax on line ${index + 1}.');
    if (equals < 1) invalid();
    final key = line.substring(0, equals).trim();
    if (!RegExp(r'^[A-Za-z_][A-Za-z0-9_]*$').hasMatch(key)) invalid();
    final raw = line.substring(equals + 1).trimLeft();
    if (raw.startsWith('"') || raw.startsWith("'")) {
      final quote = raw[0];
      final value = StringBuffer();
      var closed = false;
      for (var i = 1; i < raw.length; i++) {
        final char = raw[i];
        if (char == quote) {
          final rest = raw.substring(i + 1).trimLeft();
          if (rest.isNotEmpty && !rest.startsWith('#')) invalid();
          closed = true;
          break;
        }
        if (quote == '"' && char == r'\') {
          if (++i >= raw.length) invalid();
          switch (raw[i]) {
            case 'n':
              value.write('\n');
            case 'r':
              value.write('\r');
            case 't':
              value.write('\t');
            case r'\':
              value.write(r'\');
            case '"':
              value.write('"');
            default:
              invalid();
          }
        } else {
          value.write(char);
        }
      }
      if (!closed) invalid();
      values[key] = value.toString();
    } else {
      final comment = RegExp(r'(^|\s)#').firstMatch(raw);
      values[key] =
          (comment == null ? raw : raw.substring(0, comment.start)).trimRight();
    }
  }
  return Map.unmodifiable(values);
}