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//! Propagates [`#[doc(cfg(...))]`](https://github.com/rust-lang/rust/issues/43781) to child items.
use std::sync::Arc;
use crate::clean::cfg::Cfg;
use crate::clean::inline::{load_attrs, merge_attrs};
use crate::clean::{Crate, Item, ItemKind};
use crate::core::DocContext;
use crate::fold::DocFolder;
use crate::passes::Pass;
use rustc_hir::def_id::LocalDefId;
pub(crate) const PROPAGATE_DOC_CFG: Pass = Pass {
name: "propagate-doc-cfg",
run: propagate_doc_cfg,
description: "propagates `#[doc(cfg(...))]` to child items",
};
pub(crate) fn propagate_doc_cfg(cr: Crate, cx: &mut DocContext<'_>) -> Crate {
CfgPropagator { parent_cfg: None, parent: None, cx }.fold_crate(cr)
}
struct CfgPropagator<'a, 'tcx> {
parent_cfg: Option<Arc<Cfg>>,
parent: Option<LocalDefId>,
cx: &'a mut DocContext<'tcx>,
}
impl<'a, 'tcx> CfgPropagator<'a, 'tcx> {
// Some items need to merge their attributes with their parents' otherwise a few of them
// (mostly `cfg` ones) will be missing.
fn merge_with_parent_attributes(&mut self, item: &mut Item) {
let check_parent = match &*item.kind {
// impl blocks can be in different modules with different cfg and we need to get them
// as well.
ItemKind::ImplItem(_) => false,
kind if kind.is_non_assoc() => true,
_ => return,
};
let Some(def_id) = item.item_id.as_def_id().and_then(|def_id| def_id.as_local())
else { return };
if check_parent {
let expected_parent = self.cx.tcx.opt_local_parent(def_id);
// If parents are different, it means that `item` is a reexport and we need
// to compute the actual `cfg` by iterating through its "real" parents.
if self.parent.is_some() && self.parent == expected_parent {
return;
}
}
let mut attrs = Vec::new();
let mut next_def_id = def_id;
while let Some(parent_def_id) = self.cx.tcx.opt_local_parent(next_def_id) {
attrs.extend_from_slice(load_attrs(self.cx, parent_def_id.to_def_id()));
next_def_id = parent_def_id;
}
let (_, cfg) =
merge_attrs(self.cx, item.attrs.other_attrs.as_slice(), Some((&attrs, None)));
item.cfg = cfg;
}
}
impl<'a, 'tcx> DocFolder for CfgPropagator<'a, 'tcx> {
fn fold_item(&mut self, mut item: Item) -> Option<Item> {
let old_parent_cfg = self.parent_cfg.clone();
self.merge_with_parent_attributes(&mut item);
let new_cfg = match (self.parent_cfg.take(), item.cfg.take()) {
(None, None) => None,
(Some(rc), None) | (None, Some(rc)) => Some(rc),
(Some(mut a), Some(b)) => {
let b = Arc::try_unwrap(b).unwrap_or_else(|rc| Cfg::clone(&rc));
*Arc::make_mut(&mut a) &= b;
Some(a)
}
};
self.parent_cfg = new_cfg.clone();
item.cfg = new_cfg;
let old_parent =
if let Some(def_id) = item.item_id.as_def_id().and_then(|def_id| def_id.as_local()) {
self.parent.replace(def_id)
} else {
self.parent.take()
};
let result = self.fold_item_recur(item);
self.parent_cfg = old_parent_cfg;
self.parent = old_parent;
Some(result)
}
}
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