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//! Derive macro for `bevy_simple_prefs`.
extern crate proc_macro;
use proc_macro::TokenStream;
use quote::quote;
use syn::{Data, DeriveInput, Fields, parse_macro_input};
/// Derive macro for `bevy_simple_prefs`.
#[proc_macro_derive(Prefs)]
pub fn prefs_derive(input: TokenStream) -> TokenStream {
// Parse the input tokens into a syntax tree
let input = parse_macro_input!(input as DeriveInput);
// Get the struct name
let name = &input.ident;
// Generate the code
let expanded = match input.data {
Data::Struct(ref data_struct) => {
let mut field_bindings = Vec::new();
let mut field_checks = Vec::new();
let mut fields = Vec::new();
let mut field_assignments = Vec::new();
let mut field_inits = Vec::new();
let mut field_inserts = Vec::new();
// This ensures field_checks will not generate an empty if expression.
field_checks.push(quote! { true });
// Iterate over the fields of the struct
match &data_struct.fields {
Fields::Named(fields_named) => {
for field in &fields_named.named {
let field_name = &field.ident;
let field_type = &field.ty;
field_bindings.push(quote! {
let #field_name = world.get_resource_ref::<#field_type>().unwrap();
});
field_checks.push(quote! {
!#field_name.is_changed()
});
fields.push(quote! {
#field_name: #field_type
});
field_assignments.push(quote! {
#field_name: #field_name.clone()
});
field_inits.push(quote! {
app.init_resource::<#field_type>();
});
field_inserts.push(quote! {
world.insert_resource(val.#field_name);
});
}
}
_ => {
unimplemented!("Prefs can only be derived for structs with named fields")
}
}
quote! {
impl Prefs for #name {
fn save(world: &mut World) {
#(#field_bindings)*
if #(#field_checks)&&* {
return;
}
// Prevent saving from happening on the initial change detection after
// inserting the resources on load.
let status = world.get_resource_ref::<::bevy_simple_prefs::PrefsStatus<#name>>().unwrap();
if status.is_changed() {
return;
}
::bevy::log::debug!("Spawning save task");
let to_save = #name {
#(#field_assignments,)*
};
let settings = world.resource::<::bevy_simple_prefs::PrefsSettings<#name>>();
#[cfg(not(target_arch = "wasm32"))]
let path = settings.path.clone();
#[cfg(target_arch = "wasm32")]
let local_storage_key = settings.local_storage_key.clone();
::bevy::tasks::IoTaskPool::get()
.spawn(async move {
let Ok(serialized_value) = ::bevy_simple_prefs::serialize(&to_save) else {
::bevy::log::error!("Failed to serialize prefs.");
return;
};
#[cfg(not(target_arch = "wasm32"))]
{
::bevy::log::debug!("Saving {}", path.to_string_lossy());
::bevy_simple_prefs::save_str(&path, &serialized_value);
}
#[cfg(target_arch = "wasm32")]
{
::bevy::log::debug!("Saving {}", local_storage_key);
::bevy_simple_prefs::save_str(&local_storage_key, &serialized_value);
}
}).detach();
}
fn load(world: &mut World) {
::bevy::log::debug!("Spawning load task");
let settings = world.resource::<::bevy_simple_prefs::PrefsSettings<#name>>();
#[cfg(not(target_arch = "wasm32"))]
let path = settings.path.clone();
#[cfg(target_arch = "wasm32")]
let local_storage_key = settings.local_storage_key.clone();
let entity = world.spawn_empty().id();
let task = ::bevy::tasks::IoTaskPool::get().spawn(async move {
let val = (|| {
#[cfg(not(target_arch = "wasm32"))]
let maybe_serialized_value = {
::bevy::log::debug!("Loading {}", path.to_string_lossy());
::bevy_simple_prefs::load_str(&path)
};
#[cfg(target_arch = "wasm32")]
let maybe_serialized_value = {
::bevy::log::debug!("Loading {}", local_storage_key);
::bevy_simple_prefs::load_str(&local_storage_key)
};
let Some(serialized_value) = maybe_serialized_value else {
return #name::default();
};
match ::bevy_simple_prefs::deserialize(&serialized_value) {
Ok(v) => v,
Err(e) => {
::bevy::log::error!("Failed to deserialize prefs: {}", e);
return #name::default();
}
}
})();
let mut command_queue = ::bevy::ecs::world::CommandQueue::default();
command_queue.push(move |world: &mut World| {
#(#field_inserts;)*;
world.resource_mut::<::bevy_simple_prefs::PrefsStatus<#name>>().loaded = true;
world.despawn(entity);
});
command_queue
});
world.entity_mut(entity).insert(::bevy_simple_prefs::LoadPrefsTask(task));
}
fn init(app: &mut App) {
#(#field_inits;)*
}
}
}
}
_ => unimplemented!("Prefs can only be derived for structs"),
};
// Hand the output tokens back to the compiler
TokenStream::from(expanded)
}