Negative TimeSpan result when hours are 0 is converted to positive

[euantorano]

When running a query that returns a TimeSpan value, if the value is a negative value less than 1 hour, the timespan is converted into a positive.

For example, take the following query:

SELECT TIMEDIFF(DATE_SUB(NOW(), INTERVAL 5 MINUTE), NOW()) AS span;

The expected result would be: -00:05:00

Now, when running that query with the following code, the value is actually 00:05:00:

using (MySqlConnection connection = new MySqlConnection(connectionString))
{
    connection.Open();

    const string query = @"SELECT TIMEDIFF(DATE_SUB(NOW(), INTERVAL 5 MINUTE), NOW()) AS span;";

    using (MySqlCommand cmd = new MySqlCommand(query, connection))
    {
        object result = cmd.ExecuteScalar();

        if (result is TimeSpan ts)
        {
            Console.WriteLine($"Got timespan result: {ts}");
        }
        else
        {
            Console.WriteLine($"Got result of invalid type '{result.GetType().Name}': {result}");
        }
    }
}

I've tracked this issue down to the following line of code:

MySqlConnector/src/MySqlConnector/Core/Row.cs

Line 534 in d6288a2

if (!Utf8Parser.TryParse(value, out int hours, out var bytesConsumed))

Looking at the source for Utf8Parser.TryParse, it looks like if the value is 0, the sign in front will be lost (eg: -0 becomes 0): https://github.com/dotnet/corefx/blob/master/src/System.Memory/src/System/Buffers/Text/Utf8Parser/Utf8Parser.Number.cs#L17

Looking at Utf8Parser.TryParse(ReadOnlySpan<byte> source, out TimeSpan value, out int bytesConsumed, char standardFormat = default)), they handle any sign at the start before parsing any further: https://github.com/dotnet/corefx/blob/master/src/System.Memory/src/System/Buffers/Text/Utf8Parser/Utf8Parser.TimeSpan.BigG.cs#L28

I wonder if it's possible for MySqlConnector to simple use Utf8Parser.TryParse(ReadOnlySpan<byte> source, out TimeSpan value, out int bytesConsumed, char standardFormat = default))?

[bgrainger]

I wonder if it's possible for MySqlConnector to simple use Utf8Parser.TryParse(ReadOnlySpan<byte> source, out TimeSpan value, out int bytesConsumed, char standardFormat = default))?

Yes, it looks like this is possible, and would fix the bug.

This is not possible, because MySQL "TIME values may range from '-838:59:59' to '838:59:59'", which is not a valid format for Utf8Parser.

The fix is probably to detect a leading - and set a Boolean flag, rather than depending on hours being negative.

[bgrainger]

Fixed in 0.42.1.