serde/test_suite/tests/bytes/mod.rs

use serde::de::{Deserializer, Error, SeqAccess, Visitor};
use std::fmt;

pub fn deserialize<'de, D>(deserializer: D) -> Result<Vec<u8>, D::Error>
where
    D: Deserializer<'de>,
{
    deserializer.deserialize_byte_buf(ByteBufVisitor)
}

struct ByteBufVisitor;

impl<'de> Visitor<'de> for ByteBufVisitor {
    type Value = Vec<u8>;

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

    fn visit_seq<V>(self, mut visitor: V) -> Result<Self::Value, V::Error>
    where
        V: SeqAccess<'de>,
    {
        let mut values = Vec::new();
        while let Some(value) = visitor.next_element()? {
            values.push(value);
        }
        Ok(values)
    }

    fn visit_bytes<E>(self, v: &[u8]) -> Result<Self::Value, E>
    where
        E: Error,
    {
        Ok(v.to_vec())
    }

    fn visit_byte_buf<E>(self, v: Vec<u8>) -> Result<Self::Value, E>
    where
        E: Error,
    {
        Ok(v)
    }

    fn visit_str<E>(self, v: &str) -> Result<Self::Value, E>
    where
        E: Error,
    {
        Ok(v.as_bytes().to_vec())
    }

    fn visit_string<E>(self, v: String) -> Result<Self::Value, E>
    where
        E: Error,
    {
        Ok(v.into_bytes())
    }
}