formars

Schema validation for Rust, behind one dependency and one import. Schemas are values you compose with builders — not attributes on structs — then parse, validate, and inspect. Opt-in feature tiers add reactive headless form state, Leptos UI components, and a derive macro.

use formars::prelude::*;

let user = object()
    .field("email", string().email())
    .field("age", coerced::<u32>()); // HTML form inputs arrive as strings

let mut input = formars::formars_core::value::Object::new();
input.insert("email", Value::from("ada@example.com"));
input.insert("age", Value::from("36"));

let parsed = user.parse(&input).expect("valid input");
assert_eq!(parsed.get("age"), Some(&Value::I64(36)));

This is the default tier — schemas and typed errors, zero extra dependencies. Feature flags unlock the rest:

Enable tiers in Cargo.toml:

[dependencies]
formars = { version = "0.1", features = ["ui", "derive"] }

• Reactive forms: FormController registers fields, tracks touched/dirty, brackets submits, and merges server errors — headless and wasm-friendly (formars-signals).
• Leptos components: <Form> submit wrapper with double-submit shielding, <TextField> with bidirectional value bridging (formars-ui, Leptos 0.8).
• Derive: #[derive(FormSchema)] generates a companion schema from a plain named-field struct (formars-derive; the macro runs on the host compiler, so wasm consumers pay nothing extra).

Status

Pre-0.1: the API is still allowed to change before the first release.

Repository

See the workspace README for the full guide, architecture notes, and the CI gate battery.

License

MIT — see LICENSE.