Chrono can't parse a date from iso8601

[iddm]

Some server sends me the date time in the json:

"creationTime": "2017-06-22 13:32:16Z",

But I can't parse it neither trough Datetime nor NaiveDateTime. However, if I change the space between the date and the time to T as in 2017-06-22T13:32:16Z it parses okay.

I could not find any information does this conform iso8601 or not, different sources say different answers, iso8601. If it is iso8601 so the chrono must be able to parse it.

[quodlibetor]

ISO 8601 (and RFC 3339) both require the T.

The readme contains examples for parsing a datetime that includes a space, if you'd like.

[iddm]

@quodlibetor I don't parse it manually, I use serde for this. If I did that manually, I would have everything okay of course. I have also found the resources you told but some other resources also treat a datetime stamp without T as correct, however, I have not seen anything like that before today. I have told the api writer of the service I use to add T to the timestamp.

[quodlibetor]

In that case if you need to use it you can write my_custom_deserializer module (like we have for timestamps) that parses your format, if the service you're interacting with doesn't support it.

Something like the following (untested) code:

pub mod custom_deserialize {
    use std::fmt;
    use serde::de;

    use chrono::NaiveDateTime;

    struct NaiveDateTimeFromMyFormatVisitor;

    pub fn deserialize<'de, D>(d: D) -> Result<NaiveDateTime, D::Error>
        where D: de::Deserializer<'de>
    {
        Ok(try!(d.deserialize_str(NaiveDateTimeFromMyFormatVisitor)))
    }

    impl<'de> de::Visitor<'de> for NaiveDateTimeFromSecondsVisitor {
        type Value = NaiveDateTime;

        fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result
        {
            write!(formatter, "a datetime string")
        }

        fn visit_str<E>(self, value: &str) -> Result<NaiveDateTime, E>
            where E: de::Error
        {
            DateTime::parse_from_str(value, "%Y-%m-%d %H:%M:%S%z")
                .map_err(|e| E::custom(format!("Parse error {} for {}", e, value)))
        }
    }
}

Should allow you to use serde's #[serde(deserialize_with = "custom_deserialize::deserialize")] attribute in your struct.

[iddm]

@quodlibetor thanks a lot, I will try that if the resource refuse to support the correct version of time stamp.

[iddm]

@quodlibetor the service api author gave me this link which says the T may be omitted. What do you think?

[quodlibetor]

Ha, the specific text in the note in wikipedia is:

4.3.2 NOTE: By mutual agreement of the partners in information interchange, the character [T] may be omitted in applications where there is no risk of confusing a date and time of day representation with others defined in this International Standard.

so, if you agree that the T may be omitted then the format can still be considered ISO-8601 compliant 😄 It still wouldn't be RFC 3339 compliant, though.

Adding the ability to accept the space would require an attempted parse and a fallback. That seems like an unacceptable hidden performance hit for default behavior.

I'll investigate alternate parsing techniques, but it won't be super fast, our current code is pretty... specific.

If you want to accept strings in the format that you are currently receiving I'd recommend going with the alternate deserialization I described in a previous comment.