rulemorph 0.3.3

YAML-based declarative data transformation engine for CSV/JSON to JSON
Documentation 
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use std::collections::HashSet;
use std::fmt;

use serde::Deserializer;
use serde::de::{self, DeserializeSeed, MapAccess, SeqAccess, Visitor};
use serde_json::{Map as JsonMap, Number as JsonNumber, Value as JsonValue};

pub fn parse_json_value_strict(source: &str) -> Result<JsonValue, String> {
    let mut deserializer = serde_json::Deserializer::from_str(source);
    let value = JsonValueSeed
        .deserialize(&mut deserializer)
        .map_err(|err| err.to_string())?;
    deserializer.end().map_err(|err| err.to_string())?;
    Ok(value)
}

struct JsonValueSeed;

impl<'de> DeserializeSeed<'de> for JsonValueSeed {
    type Value = JsonValue;

    fn deserialize<D>(self, deserializer: D) -> Result<Self::Value, D::Error>
    where
        D: Deserializer<'de>,
    {
        deserializer.deserialize_any(JsonValueVisitor)
    }
}

struct JsonValueVisitor;

impl<'de> Visitor<'de> for JsonValueVisitor {
    type Value = JsonValue;

    fn expecting(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
        formatter.write_str("a JSON value")
    }

    fn visit_bool<E>(self, value: bool) -> Result<Self::Value, E> {
        Ok(JsonValue::Bool(value))
    }

    fn visit_i64<E>(self, value: i64) -> Result<Self::Value, E> {
        Ok(JsonValue::Number(value.into()))
    }

    fn visit_u64<E>(self, value: u64) -> Result<Self::Value, E> {
        Ok(JsonValue::Number(value.into()))
    }

    fn visit_f64<E>(self, value: f64) -> Result<Self::Value, E>
    where
        E: de::Error,
    {
        JsonNumber::from_f64(value)
            .map(JsonValue::Number)
            .ok_or_else(|| E::custom("non-finite JSON number is not allowed"))
    }

    fn visit_str<E>(self, value: &str) -> Result<Self::Value, E>
    where
        E: de::Error,
    {
        Ok(JsonValue::String(value.to_string()))
    }

    fn visit_string<E>(self, value: String) -> Result<Self::Value, E>
    where
        E: de::Error,
    {
        Ok(JsonValue::String(value))
    }

    fn visit_none<E>(self) -> Result<Self::Value, E> {
        Ok(JsonValue::Null)
    }

    fn visit_unit<E>(self) -> Result<Self::Value, E> {
        Ok(JsonValue::Null)
    }

    fn visit_seq<A>(self, mut seq: A) -> Result<Self::Value, A::Error>
    where
        A: SeqAccess<'de>,
    {
        let mut values = Vec::with_capacity(seq.size_hint().unwrap_or(0));
        while let Some(value) = seq.next_element_seed(JsonValueSeed)? {
            values.push(value);
        }
        Ok(JsonValue::Array(values))
    }

    fn visit_map<A>(self, mut map: A) -> Result<Self::Value, A::Error>
    where
        A: MapAccess<'de>,
    {
        let mut values = JsonMap::new();
        let mut keys = HashSet::new();
        while let Some(key) = map.next_key::<String>()? {
            if !keys.insert(key.clone()) {
                return Err(de::Error::custom(format!("duplicate key `{}`", key)));
            }
            let value = map.next_value_seed(JsonValueSeed)?;
            values.insert(key, value);
        }
        Ok(JsonValue::Object(values))
    }
}