1 files changed, 290 insertions, 0 deletions
diff --git a/src/utils.rs b/src/utils.rs
new file mode 100644
index 0000000..c8b3457
--- /dev/null
+++ b/src/utils.rs
@@ -0,0 +1,290 @@
+use serde::{
+    de::{self, DeserializeSeed, Deserializer, EnumAccess, SeqAccess, VariantAccess, Visitor},
+    forward_to_deserialize_any,
+    ser::{self, Impossible, Serialize, SerializeSeq, SerializeTupleVariant, Serializer},
+};
+use std::fmt;
+
+/// A wrapper for serializing and deserializing enums in the way Yojson expects. Based off of
+/// [this](https://github.com/serde-rs/serde/issues/979#issuecomment-350340431).
+pub struct EnumAsArray<T>(pub T);
+
+fn expected_enum<T, E>() -> Result<T, E>
+where
+    E: ser::Error,
+{
+    Err(ser::Error::custom(
+        "EnumAsArray expected to operate on an enum type",
+    ))
+}
+
+impl<S> Serializer for EnumAsArray<S>
+where
+    S: Serializer,
+{
+    type Ok = S::Ok;
+    type Error = S::Error;
+
+    type SerializeSeq = Impossible<Self::Ok, Self::Error>;
+    type SerializeTuple = Impossible<Self::Ok, Self::Error>;
+    type SerializeTupleStruct = Impossible<Self::Ok, Self::Error>;
+    type SerializeTupleVariant = EnumAsArray<S::SerializeSeq>;
+    type SerializeMap = Impossible<Self::Ok, Self::Error>;
+    type SerializeStruct = Impossible<Self::Ok, Self::Error>;
+    type SerializeStructVariant = Impossible<Self::Ok, Self::Error>;
+
+    fn serialize_bool(self, _v: bool) -> Result<Self::Ok, Self::Error> {
+        expected_enum()
+    }
+    fn serialize_i8(self, _v: i8) -> Result<Self::Ok, Self::Error> {
+        expected_enum()
+    }
+    fn serialize_i16(self, _v: i16) -> Result<Self::Ok, Self::Error> {
+        expected_enum()
+    }
+    fn serialize_i32(self, _v: i32) -> Result<Self::Ok, Self::Error> {
+        expected_enum()
+    }
+    fn serialize_i64(self, _v: i64) -> Result<Self::Ok, Self::Error> {
+        expected_enum()
+    }
+    fn serialize_u8(self, _v: u8) -> Result<Self::Ok, Self::Error> {
+        expected_enum()
+    }
+    fn serialize_u16(self, _v: u16) -> Result<Self::Ok, Self::Error> {
+        expected_enum()
+    }
+    fn serialize_u32(self, _v: u32) -> Result<Self::Ok, Self::Error> {
+        expected_enum()
+    }
+    fn serialize_u64(self, _v: u64) -> Result<Self::Ok, Self::Error> {
+        expected_enum()
+    }
+    fn serialize_f32(self, _v: f32) -> Result<Self::Ok, Self::Error> {
+        expected_enum()
+    }
+    fn serialize_f64(self, _v: f64) -> Result<Self::Ok, Self::Error> {
+        expected_enum()
+    }
+    fn serialize_char(self, _v: char) -> Result<Self::Ok, Self::Error> {
+        expected_enum()
+    }
+    fn serialize_str(self, _v: &str) -> Result<Self::Ok, Self::Error> {
+        expected_enum()
+    }
+    fn serialize_bytes(self, _v: &[u8]) -> Result<Self::Ok, Self::Error> {
+        expected_enum()
+    }
+    fn serialize_none(self) -> Result<Self::Ok, Self::Error> {
+        expected_enum()
+    }
+    fn serialize_some<T: ?Sized + Serialize>(self, _value: &T) -> Result<Self::Ok, Self::Error> {
+        expected_enum()
+    }
+    fn serialize_unit(self) -> Result<Self::Ok, Self::Error> {
+        expected_enum()
+    }
+    fn serialize_unit_struct(self, _name: &'static str) -> Result<Self::Ok, Self::Error> {
+        expected_enum()
+    }
+    fn serialize_unit_variant(
+        self,
+        _name: &'static str,
+        _variant_index: u32,
+        variant: &'static str,
+    ) -> Result<Self::Ok, Self::Error> {
+        let mut seq = self.0.serialize_seq(Some(1))?;
+        seq.serialize_element(variant)?;
+        seq.end()
+    }
+    fn serialize_newtype_struct<T: ?Sized + Serialize>(
+        self,
+        _name: &'static str,
+        _value: &T,
+    ) -> Result<Self::Ok, Self::Error> {
+        expected_enum()
+    }
+    fn serialize_newtype_variant<T: ?Sized + Serialize>(
+        self,
+        _name: &'static str,
+        _variant_index: u32,
+        variant: &'static str,
+        value: &T,
+    ) -> Result<Self::Ok, Self::Error> {
+        let mut seq = self.0.serialize_seq(Some(2))?;
+        seq.serialize_element(variant)?;
+        seq.serialize_element(value)?;
+        seq.end()
+    }
+    fn serialize_seq(self, _len: Option<usize>) -> Result<Self::SerializeSeq, Self::Error> {
+        expected_enum()
+    }
+    fn serialize_tuple(self, _len: usize) -> Result<Self::SerializeTuple, Self::Error> {
+        expected_enum()
+    }
+    fn serialize_tuple_struct(
+        self,
+        _name: &'static str,
+        _len: usize,
+    ) -> Result<Self::SerializeTupleStruct, Self::Error> {
+        expected_enum()
+    }
+    fn serialize_tuple_variant(
+        self,
+        _name: &'static str,
+        _variant_index: u32,
+        variant: &'static str,
+        len: usize,
+    ) -> Result<Self::SerializeTupleVariant, Self::Error> {
+        let mut seq = self.0.serialize_seq(Some(1 + len))?;
+        seq.serialize_element(variant)?;
+        Ok(EnumAsArray(seq))
+    }
+    fn serialize_map(self, _len: Option<usize>) -> Result<Self::SerializeMap, Self::Error> {
+        expected_enum()
+    }
+    fn serialize_struct(
+        self,
+        _name: &'static str,
+        _len: usize,
+    ) -> Result<Self::SerializeStruct, Self::Error> {
+        expected_enum()
+    }
+    fn serialize_struct_variant(
+        self,
+        _name: &'static str,
+        _variant_index: u32,
+        _variant: &'static str,
+        _len: usize,
+    ) -> Result<Self::SerializeStructVariant, Self::Error> {
+        Err(ser::Error::custom(
+            "enum_as_array::serialize does not support struct variants",
+        ))
+    }
+}
+
+impl<S> SerializeTupleVariant for EnumAsArray<S>
+where
+    S: SerializeSeq,
+{
+    type Ok = S::Ok;
+    type Error = S::Error;
+
+    fn serialize_field<T: ?Sized + Serialize>(&mut self, value: &T) -> Result<(), Self::Error> {
+        self.0.serialize_element(value)
+    }
+    fn end(self) -> Result<Self::Ok, Self::Error> {
+        self.0.end()
+    }
+}
+
+impl<'de, D> Deserializer<'de> for EnumAsArray<D>
+where
+    D: Deserializer<'de>,
+{
+    type Error = D::Error;
+
+    fn deserialize_any<V>(self, _visitor: V) -> Result<V::Value, Self::Error>
+    where
+        V: Visitor<'de>,
+    {
+        Err(de::Error::custom(
+            "EnumAsArray expected to operate on an enum type",
+        ))
+    }
+
+    fn deserialize_enum<V>(
+        self,
+        _name: &'static str,
+        _variants: &'static [&'static str],
+        visitor: V,
+    ) -> Result<V::Value, Self::Error>
+    where
+        V: Visitor<'de>,
+    {
+        self.0.deserialize_seq(EnumAsArray(visitor))
+    }
+
+    forward_to_deserialize_any! {
+        bool i8 i16 i32 i64 u8 u16 u32 u64 f32 f64 char str string bytes
+        byte_buf option unit unit_struct newtype_struct seq tuple
+        tuple_struct map struct identifier ignored_any
+    }
+}
+
+impl<'de, V> Visitor<'de> for EnumAsArray<V>
+where
+    V: Visitor<'de>,
+{
+    type Value = V::Value;
+
+    fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        self.0.expecting(formatter)
+    }
+
+    fn visit_seq<A>(self, seq: A) -> Result<Self::Value, A::Error>
+    where
+        A: SeqAccess<'de>,
+    {
+        self.0.visit_enum(EnumAsArray(seq))
+    }
+}
+
+impl<'de, A> EnumAccess<'de> for EnumAsArray<A>
+where
+    A: SeqAccess<'de>,
+{
+    type Error = A::Error;
+    type Variant = Self;
+
+    fn variant_seed<V>(mut self, seed: V) -> Result<(V::Value, Self::Variant), Self::Error>
+    where
+        V: DeserializeSeed<'de>,
+    {
+        match self.0.next_element_seed(seed)? {
+            Some(first) => Ok((first, self)),
+            None => Err(de::Error::custom("expected at least one element")),
+        }
+    }
+}
+
+impl<'de, A> VariantAccess<'de> for EnumAsArray<A>
+where
+    A: SeqAccess<'de>,
+{
+    type Error = A::Error;
+
+    fn unit_variant(self) -> Result<(), Self::Error> {
+        Ok(())
+    }
+
+    fn newtype_variant_seed<T>(mut self, seed: T) -> Result<T::Value, Self::Error>
+    where
+        T: DeserializeSeed<'de>,
+    {
+        match self.0.next_element_seed(seed)? {
+            Some(newtype) => Ok(newtype),
+            None => Err(de::Error::custom("missing newtype variant value")),
+        }
+    }
+
+    fn tuple_variant<V>(self, _len: usize, visitor: V) -> Result<V::Value, Self::Error>
+    where
+        V: Visitor<'de>,
+    {
+        visitor.visit_seq(self.0)
+    }
+
+    fn struct_variant<V>(
+        self,
+        _fields: &'static [&'static str],
+        _visitor: V,
+    ) -> Result<V::Value, Self::Error>
+    where
+        V: Visitor<'de>,
+    {
+        Err(de::Error::custom(
+            "EnumAsArray does not support struct variants",
+        ))
+    }
+}