StringUtil#splitOnEverySecondWhiteSpace returns empty collection when string with no whitespace is passed as argument.

[Trup10ka]

This bug causes functions which use it to act how they should not.

String parsing function:

    @NotNull
    public static List<@NotNull String> splitOnEverySecondWhiteSpace(@NotNull String args)
    {
        String regex = "(\\S+\\s+\\S+)";
        Pattern pattern = Pattern.compile(regex);
        Matcher matcher = pattern.matcher(args);

        List<String> result = new ArrayList<>();

        while (matcher.find())
        {
            result.add(matcher.group());
        }

        return result;
    }

For example, when parsing arguments in:

    @Override
    @NotNull
    public Map<String, @Nullable String> parse(@NotNull String args, @NotNull String keyValueDelimiter)
    {
        Map<String, @Nullable String> result = new HashMap<>();
        List<String> pairs = StringUtil.splitOnEverySecondWhiteSpace(args);
        List<String> validKeys = Arrays.asList(keys);

        for (String pair : pairs)
        {
            String[] keyValue = pair.split(keyValueDelimiter);
            if (keyValue.length != 2 || keyValue[1].isEmpty())
            {
                throw new IllegalArgumentException("Missing value for key: " + keyValue[0]);
            }
            if (!validKeys.contains(keyValue[0]))
            {
                System.out.println("Unrecognized key: " + keyValue[0]);
                return new HashMap<>();
            }
            result.put(keyValue[0], keyValue[1]);
        }
        return result;
    }

If we enter in console:

kappa> cc -fn

expected output should be:

kappa> cc -fn
Missing value for '-fn' key

but actual is

Failed to parse arguments