typed-geojson

Strongly-typed GeoJSON for Rust. Feature<G, P> / FeatureCollection<G, P>: generic over Geometry and Properties, layered over the georust geojson crate. With the specta feature it exports to TypeScript that is mutually assignable with @types/geojson.

use serde::{Deserialize, Serialize};
use typed_geojson::{Feature, Geometry};

#[derive(Serialize, Deserialize, PartialEq, Debug)]
struct Station { id: u32, name: String, temp_c: f64 }

let raw = r#"{
    "type": "Feature",
    "geometry": { "type": "Point", "coordinates": [-96.8, 32.8] },
    "properties": { "id": 7, "name": "DFW", "temp_c": 31.5 }
}"#;

let feature: Feature<Geometry, Station> = serde_json::from_str(raw).unwrap();
assert_eq!(feature.properties.name, "DFW");

What you get

• Feature<G, P> / FeatureCollection<G, P>: native parameter order; G defaults to the [Geometry] union, P to an untyped JSON object.
• Typed geometry (Point, LineString, Polygon, MultiPoint, MultiLineString, MultiPolygon, GeometryCollection, and the Geometry union), each matching its native @types/geojson shape.
• serde that round-trips to/from spec GeoJSON: validates "type", tolerates foreign members, keeps id/bbox, omits an absent bbox.
• TryFrom bridges to/from the untyped geojson crate.

Nullability lives in G

Geometry is required but may be null (RFC 7946); like native, that nullability is a choice of G:

type Located   = Feature<Geometry, Props>;          // geometry: Geometry  (non-null)
type Unlocated = Feature<Option<Geometry>, Props>;  // geometry: Geometry | null
type PointFeat = Feature<Point, Props>;             // geometry: Point

TypeScript (specta feature)

Feature<Point, Props> exports to a TS Feature<Point, Props> assignable to and from GeoJSON.Feature<GeoJSON.Point, Props>: zero tsc errors, both ways.

let types = typed_geojson::specta_types();
let ts = specta_typescript::Typescript::default()
    .export(&types, specta_serde::Format)?;

Two details make it line up: bbox is a tuple union ([n,n,n,n] | [n,…×6]), not number[]; each geometry's "type" is a string literal. ts/ holds the assignability harness, gated in CI by tsc --noEmit.

Benchmarks

cargo bench, a 1k-point FeatureCollection with typed properties, vs the untyped geojson baseline:

Typed is ~30% faster to deserialize (typed properties skip the untyped JSON map); the untagged Geometry union adds ~16% on reads. Serialize is on par.

License

Licensed under either Apache-2.0 or MIT at your option. Contributions are dual-licensed as above unless stated otherwise.