Fill missing ids

A hand-written entry may leave id out. The checker warns about it as missing-id, the scene still loads, and references to it go by name. Project::fix fills the missing ids of every file a scene or prefab reads: the file, its includes, its libraries, the prefabs it places and its proxies file.

use std::path::Path;

use pfx_scene::Project;

fn main() {
    let project = Project::open(Path::new("my-game")).unwrap();
    let group = project.fix(Path::new("scenes/room.scene.toml")).unwrap();
    if group.is_empty() {
        println!("every entry has its id");
        return;
    }
    for file in group.files() {
        println!("fills ids in {}", file.display());
    }
    group.write().unwrap();
}

fix writes nothing itself: it returns the patch group, checked as a whole, and write() writes it, refused when a file no longer holds the text the group starts from. A scene that does not load is refused with its errors in EditError::diagnostics, and a format 0 file is refused too: migrate it, which writes its ids. An editor that opens a scene through SceneEdit fills them on its first write of each file.

How a filled id is made

A filled id is derived, not random: Id::derive of the file’s project-relative path, the entry’s kind and its name, the first 50 bits of their SHA-256. Running fix twice on the same project gives the same ids, and an id already taken anywhere in the project is skipped. The crate reads no clock and no system randomness.

Ids for new entries

When your tool adds an entry, give it an id: random for an entry a person adds, or derived from a stable key your tool owns, so a build gives the same bytes for the same input.

use pfx_scene::Id;

let random_bits: u64 = 0x1234_5678_9abc;
let made = Id::from_bits(random_bits);
let derived = Id::derive(b"levels/one.scene.toml\nobject\ndoor");

Id::from_bits keeps the low 50 bits. An id is 10 lowercase Crockford base32 characters; once written it never changes, so renaming or moving an entry keeps its references.