1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131

use serde;

pub type OneOrMany<T> = Vec<T>;

pub fn deserialize<'de, T, D>(deserializer: D) -> Result<Vec<T>, D::Error>
    where T: serde::Deserialize<'de>,
          D: serde::Deserializer<'de>
{
    use std::marker::PhantomData;
    use std::fmt;

    use serde::de::{self, Deserialize, IntoDeserializer};
    use serde::de::value::{MapAccessDeserializer, SeqAccessDeserializer};

    struct OneOrManyDeserializer<T>(PhantomData<T>);
    impl<'de2, T> serde::de::Visitor<'de2> for OneOrManyDeserializer<T>
        where T: Deserialize<'de2>
    {
        type Value = Vec<T>;

        fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
            formatter.write_str("one or many")
        }

        fn visit_i64<E>(self, value: i64) -> Result<Vec<T>, E>
            where E: de::Error
        {
            Deserialize::deserialize(value.into_deserializer()).map(|v| vec![v])
        }

        fn visit_u64<E>(self, value: u64) -> Result<Vec<T>, E>
            where E: de::Error
        {
            Deserialize::deserialize(value.into_deserializer()).map(|v| vec![v])
        }

        fn visit_str<E>(self, value: &str) -> Result<Vec<T>, E>
            where E: de::Error
        {
            Deserialize::deserialize(value.into_deserializer()).map(|v| vec![v])
        }

        fn visit_string<E>(self, value: String) -> Result<Vec<T>, E>
            where E: de::Error
        {
            Deserialize::deserialize(value.into_deserializer()).map(|v| vec![v])
        }

        fn visit_map<V>(self, visitor: V) -> Result<Self::Value, V::Error>
            where V: serde::de::MapAccess<'de2>
        {
            Deserialize::deserialize(MapAccessDeserializer::new(visitor)).map(|v| vec![v])
        }

        fn visit_seq<V>(self, visitor: V) -> Result<Self::Value, V::Error>
            where V: serde::de::SeqAccess<'de2>
        {
            Deserialize::deserialize(SeqAccessDeserializer::new(visitor))
        }
    }
    deserializer.deserialize_any(OneOrManyDeserializer(PhantomData::<T>))
}

pub fn serialize<T, S>(value: &[T], serializer: S) -> Result<S::Ok, S::Error>
    where T: serde::Serialize,
          S: serde::Serializer
{
    use serde::Serialize;
    if value.len() == 1 {
        value[0].serialize(serializer)
    } else {
        value.serialize(serializer)
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    use serde::{Deserialize, Serialize};
    use serde_json::from_str;

    #[derive(PartialEq, Debug, Deserialize, Serialize)]
    struct OneOrMany<T>(#[serde(serialize_with="serialize", deserialize_with="deserialize")]
                        Vec<T>)
        where T: for<'de2> Deserialize<'de2> + Serialize;

    #[test]
    fn deserialize_one_int() {
        assert_eq!(from_str::<OneOrMany<i32>>("1").unwrap(), OneOrMany(vec![1]));
    }

    #[test]
    fn deserialize_many_int() {
        assert_eq!(from_str::<OneOrMany<i32>>("[1, 2, 3]").unwrap(),
                   OneOrMany(vec![1, 2, 3]));
    }

    #[derive(Deserialize, Serialize, Debug, PartialEq)]
    struct Test {
        x: i32,
        y: Option<String>,
    }

    #[test]
    fn deserialize_one_struct() {
        assert_eq!(from_str::<OneOrMany<Test>>(r#"{ "x" : 10, "y" : "test" }"#).unwrap(),
                   OneOrMany(vec![Test {
                                      x: 10,
                                      y: Some("test".to_string()),
                                  }]));
    }

    #[test]
    fn deserialize_one_struct_missing_field() {
        assert_eq!(from_str::<OneOrMany<Test>>(r#"{ "x" : 10 }"#).unwrap(),
                   OneOrMany(vec![Test { x: 10, y: None }]));
    }


    #[test]
    fn deserialize_many_struct() {
        assert_eq!(from_str::<OneOrMany<Test>>(r#"[{ "x" : 10 }, { "x" : 0, "y" : "a" }]"#)
                       .unwrap(),
                   OneOrMany(vec![Test { x: 10, y: None },
                                  Test {
                                      x: 0,
                                      y: Some("a".to_string()),
                                  }]));
    }
}