plugins/agent/provider-protocol/src/field.rs

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

//! Three-state fields for vendor metadata where absence and explicit null have
//! distinct meanings. Business options that collapse null still use Option.
use serde::{Deserialize, Deserializer, Serialize, Serializer};

#[derive(Debug, Clone, Default)]
pub enum Field<T> {
    #[default]
    Missing,
    Null,
    Value(T),
}
impl<T> Field<T> {
    pub fn is_missing(&self) -> bool {
        matches!(self, Self::Missing)
    }
    pub fn value(&self) -> Option<&T> {
        match self {
            Self::Value(value) => Some(value),
            _ => None,
        }
    }
}
impl<'de, T: Deserialize<'de>> Deserialize<'de> for Field<T> {
    fn deserialize<D: Deserializer<'de>>(deserializer: D) -> Result<Self, D::Error> {
        Ok(match Option::<T>::deserialize(deserializer)? {
            Some(value) => Self::Value(value),
            None => Self::Null,
        })
    }
}
impl<T: Serialize> Serialize for Field<T> {
    fn serialize<S: Serializer>(&self, serializer: S) -> Result<S::Ok, S::Error> {
        match self {
            Self::Value(value) => value.serialize(serializer),
            Self::Null | Self::Missing => serializer.serialize_none(),
        }
    }
}