Module discovery

Allows dependent crates to statically discover classes registered by this extension.

Rationale

The idea is to provide a mechanism that allows tools and integrations to query information about an extension at build time. For example, this allows validations, data extraction/generation, etc. It is limited to downstream crates depending on the crate declaring the extension, in particular their build.rs file. If a crate is used for discovery, then it must declare crate-type = ["cdylib", "rlib"], i.e. both a C dynamic library for GDExtension and a Rust library.

The API is kept deliberately minimal – it does not strive to cover the entire reflection API that Godot provides. Many tools may be better fitted as a direct integration into the Godot editor, or as runtime code querying Godot’s ClassDB API. If you believe this API is lacking, please provide a detailed use case.

Usage

To make use of discovery, your entry point trait needs to have the discover attribute:

/// Your tag must be public.
pub struct MyCoolGame;

/// The `discovery` attributes adds an associated `MyExtension::discover()` function to the `MyExtension` tag.
/// It also declares a module `godot_discovery` in the current scope, which re-exports symbols from `godot::init::discovery`.
/// This allows your dependent crate to not depend on `godot` directly.
#[gdextension(discovery)]
unsafe impl ExtensionLibrary for MyCoolGame {}

To access the exposed API in a dependent crate in build.rs, you can call MyExtension::discover():

use my_crate::MyCoolGame;
use my_crate::godot_discovery::DiscoveredExtension;

fn main() {
   let api: DiscoveredExtension = MyCoolGame::discover();
   for c in api.classes() {
       println!("Discovered class {}.", c.name());
   }
}

Structs

• DiscoveredClass
• DiscoveredExtension