deser-value

A dynamic value type for deser. Value can hold anything the deser data model can express. Use it for data whose structure is not known up front, to inspect or transform data before it's deserialized into a type, or to convert between formats:

use deser_value::{Value, value};

let mut config: Value =
    deser_json::from_str(r#"{"name": "app", "port": 8080}"#).unwrap();
config["port"] = value!(9090);
config["tags"] = value!(["web", "prod"]);
assert_eq!(
    deser_json::to_string(&config).unwrap(),
    r#"{"name":"app","port":9090,"tags":["web","prod"]}"#
);

Unlike most value types, a Value keeps as much of the input as possible. Deserializing a value and serializing it again gives you the same output:

Any keys: map keys can be any value (for instance integers in CBOR or complex keys in YAML). Maps keep the order of their entries.
Extensions: date-times, UUIDs, exact numbers and other extension values keep their type. A TOML date-time stays a date-time, and JSON numbers that don't fit into an f64 keep their text.
Event data: information that is not part of the data model, such as CBOR tags, YAML tags and formatting hints, is kept in the meta data of each value.
Locations: if the format tracks locations, values remember where they came from. Types deserialized from such values report errors at the original location, even after values were moved around or merged from different files:

use deser::{Context, Deserialize, TrackLocations};
use deser_value::{Value, from_value};

#[derive(Debug, Deserialize)]
struct Config {
    port: u16,
}

let config = deser_json::DeserializerConfig::builder()
    .context(Context::with(TrackLocations(true)))
    .build();
let value: Value = config.from_str("{\n  \"port\": \"80\"\n}").unwrap();
let err = from_value::<Config>(&value).unwrap_err();
assert_eq!((err.line(), err.column()), (Some(2), Some(11)));

Values are converted from and into other types with to_value and from_value. To configure the conversion (for instance to add layers) use deser_value::Serializer and deser_value::Deserializer, which work like the serializers and deserializers of the formats.

Like the rest of deser, values do not use recursion. Deeply nested values can be deserialized, serialized, cloned, compared, formatted and dropped without overflowing the stack.

deser-value 0.10.0

deser-value