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//! Module: node::def
//! Responsibility: derive-side node parsing.
//! Does not own: runtime schema semantics.
//! Boundary: macro metadata to node models.
use crate::prelude::*;
///
/// Def
///
/// the default gets overridden after the initial darling::from_list() call
/// Schema declarations are concrete types; generic parameters are rejected before emission.
///
#[derive(Debug, Default)]
pub struct Def {
pub(crate) item: Option<ItemStruct>,
paths: Option<CratePaths>,
}
impl Def {
/// Refuse authored state that generated schema types cannot preserve.
pub(crate) fn validate_declaration(item: &ItemStruct) -> Result<(), DarlingError> {
if !item.generics.params.is_empty() {
return Err(DarlingError::custom(
"schema declarations must not have generic parameters",
)
.with_span(&item.generics));
}
if !item.fields.is_empty() {
return Err(DarlingError::custom(
"schema declarations must have empty bodies; declare fields in the macro arguments",
)
.with_span(&item.fields));
}
Ok(())
}
/// Build one derive-side definition wrapper from the parsed item.
#[must_use]
pub const fn new(item: ItemStruct, paths: CratePaths) -> Self {
Self {
item: Some(item),
paths: Some(paths),
}
}
/// Preserve authored outer attributes on the main generated type.
/// Only the macro's own debug switch is consumed instead of forwarded.
pub(crate) fn type_attributes(&self) -> impl Iterator<Item = &syn::Attribute> {
self.item
.iter()
.flat_map(|item| &item.attrs)
.filter(|attr| !attr.path().is_ident("debug"))
}
/// Return the invocation paths attached before validation and emission.
///
/// # Panics
/// Panics before parsed definition metadata has been attached.
pub(crate) const fn paths(&self) -> &CratePaths {
self.paths
.as_ref()
.expect("derive definition must include resolved crate paths")
}
/// Return the parsed item identifier.
///
/// # Panics
///
/// Panics if called before darling has attached the parsed item metadata.
pub fn ident(&self) -> Ident {
self.item
.as_ref()
.unwrap_or_else(|| panic!("derive definition metadata must include the parsed item"))
.ident
.clone()
}
}
impl HasSchemaPart for Def {
fn schema_part(&self, paths: &CratePaths) -> TokenStream {
let model = &paths.model;
let ident = quote_one(&self.ident(), to_str_lit);
// quote
quote! {
#model::node::Def::new(module_path!(), #ident)
}
}
}
#[cfg(test)]
mod tests;