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|
use proc_macro::TokenStream;
use quote::{quote, ToTokens};
use syn::spanned::Spanned;
use syn::{parse, Attribute, Ident, Item, ItemEnum, ItemStruct, ItemUnion};
#[proc_macro_derive(Component, attributes(component))]
pub fn component_derive(input: TokenStream) -> TokenStream
{
let item: TypeItem = parse::<Item>(input).unwrap().try_into().unwrap();
let item_ident = item.ident();
let component_attr = item.component_attribute().unwrap_or_default();
let drop_last = component_attr.drop_last;
quote! {
impl ecs::component::Component for #item_ident
{
fn drop_last(&self) -> bool {
#drop_last
}
fn as_any_mut(&mut self) -> &mut dyn std::any::Any
{
self
}
fn as_any(&self) -> &dyn std::any::Any
{
self
}
}
impl ecs::system::Input for #item_ident {}
impl ecs::type_name::TypeName for #item_ident
{
fn type_name(&self) -> &'static str
{
std::any::type_name::<Self>()
}
}
}
.into()
}
enum TypeItem
{
Struct(ItemStruct),
Enum(ItemEnum),
Union(ItemUnion),
}
impl TypeItem
{
fn ident(&self) -> &Ident
{
match self {
Self::Struct(struct_item) => &struct_item.ident,
Self::Enum(enum_item) => &enum_item.ident,
Self::Union(union_item) => &union_item.ident,
}
}
fn component_attribute(&self) -> Option<ComponentAttribute>
{
let item_attrs = match &self {
Self::Struct(struct_item) => &struct_item.attrs,
&Self::Enum(enum_item) => &enum_item.attrs,
&Self::Union(union_item) => &union_item.attrs,
};
let mut component_attr: Option<&Attribute> = None;
for item_attr in item_attrs {
if component_attr.is_some() {
panic!("Expected only one component attribute");
}
if item_attr.path().get_ident()? == "component" {
component_attr = Some(item_attr);
}
}
Some(ComponentAttribute::from_attribute(component_attr?).unwrap())
}
}
impl TryFrom<Item> for TypeItem
{
type Error = syn::Error;
fn try_from(item: Item) -> Result<Self, Self::Error>
{
match item {
Item::Struct(struct_item) => Ok(Self::Struct(struct_item)),
Item::Enum(enum_item) => Ok(Self::Enum(enum_item)),
Item::Union(union_item) => Ok(Self::Union(union_item)),
_ => Err(syn::Error::new(
item.span(),
"Expected a struct, a enum or a union",
)),
}
}
}
impl ToTokens for TypeItem
{
fn to_tokens(&self, tokens: &mut proc_macro2::TokenStream)
{
match self {
Self::Struct(struct_item) => struct_item.to_tokens(tokens),
Self::Enum(enum_item) => enum_item.to_tokens(tokens),
Self::Union(union_item) => union_item.to_tokens(tokens),
}
}
}
#[derive(Debug, Default)]
struct ComponentAttribute
{
drop_last: bool,
}
impl ComponentAttribute
{
fn from_attribute(attribute: &Attribute) -> Result<Self, syn::Error>
{
let mut drop_last = false;
attribute.parse_nested_meta(|meta| {
if meta
.path
.get_ident()
.is_some_and(|flag| flag == "drop_last")
{
drop_last = true;
return Ok(());
}
Err(meta.error("Unrecognized token"))
})?;
Ok(Self { drop_last })
}
}
|
