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Return an iterator instead of a Vec in rustdoc Item::attributes #140441

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Return an iterator instead of a Vec in rustdoc Item::attributes #140441

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118 changes: 75 additions & 43 deletions src/librustdoc/clean/types.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -759,48 +759,9 @@ impl Item {
Some(tcx.visibility(def_id))
}

pub(crate) fn attributes(&self, tcx: TyCtxt<'_>, cache: &Cache, is_json: bool) -> Vec<String> {
const ALLOWED_ATTRIBUTES: &[Symbol] =
&[sym::export_name, sym::link_section, sym::no_mangle, sym::non_exhaustive];

fn adt_item_extra_attrs(&self, tcx: TyCtxt<'_>, document_private: bool) -> Option<String> {
use rustc_abi::IntegerType;

let mut attrs: Vec<String> = self
.attrs
.other_attrs
.iter()
.filter_map(|attr| {
if is_json {
match attr {
hir::Attribute::Parsed(AttributeKind::Deprecation { .. }) => {
// rustdoc-json stores this in `Item::deprecation`, so we
// don't want it it `Item::attrs`.
None
}
rustc_hir::Attribute::Parsed(rustc_attr_parsing::AttributeKind::Repr(
..,
)) => {
// We have separate pretty-printing logic for `#[repr(..)]` attributes.
// For example, there are circumstances where `#[repr(transparent)]`
// is applied but should not be publicly shown in rustdoc
// because it isn't public API.
None
}
_ => Some(rustc_hir_pretty::attribute_to_string(&tcx, attr)),
}
} else if attr.has_any_name(ALLOWED_ATTRIBUTES) {
Some(
rustc_hir_pretty::attribute_to_string(&tcx, attr)
.replace("\\\n", "")
.replace('\n', "")
.replace(" ", " "),
)
} else {
None
}
})
.collect();

// Add #[repr(...)]
if let Some(def_id) = self.def_id()
&& let ItemType::Struct | ItemType::Enum | ItemType::Union = self.type_()
Expand All @@ -814,7 +775,7 @@ impl Item {
if repr.transparent() {
// Render `repr(transparent)` iff the non-1-ZST field is public or at least one
// field is public in case all fields are 1-ZST fields.
let render_transparent = cache.document_private
let render_transparent = document_private
|| adt
.all_fields()
.find(|field| {
Expand Down Expand Up @@ -860,10 +821,55 @@ impl Item {
out.push(&int_s);
}
if !out.is_empty() {
attrs.push(format!("#[repr({})]", out.join(", ")));
return Some(format!("#[repr({})]", out.join(", ")));
}
}
attrs
None
}

pub(crate) fn attributes(
&self,
tcx: TyCtxt<'_>,
cache: &Cache,
is_json: bool,
) -> impl Iterator<Item = String> {
const ALLOWED_ATTRIBUTES: &[Symbol] =
&[sym::export_name, sym::link_section, sym::no_mangle, sym::non_exhaustive];

self.attrs
.other_attrs
.iter()
.filter_map(move |attr| {
if is_json {
match attr {
hir::Attribute::Parsed(AttributeKind::Deprecation { .. }) => {
// rustdoc-json stores this in `Item::deprecation`, so we
// don't want it it `Item::attrs`.
None
}
rustc_hir::Attribute::Parsed(rustc_attr_parsing::AttributeKind::Repr(
..,
)) => {
// We have separate pretty-printing logic for `#[repr(..)]` attributes.
// For example, there are circumstances where `#[repr(transparent)]`
// is applied but should not be publicly shown in rustdoc
// because it isn't public API.
None
}
_ => Some(rustc_hir_pretty::attribute_to_string(&tcx, attr)),
}
} else if attr.has_any_name(ALLOWED_ATTRIBUTES) {
let attr = rustc_hir_pretty::attribute_to_string(&tcx, attr);
Some(if attr.contains(['\n', '\\']) || attr.contains(" ") {
attr.replace("\\\n", "").replace('\n', "").replace(" ", " ")
} else {
attr
})
} else {
None
}
})
.chain(AttrIterator::new(self, cache.document_private, tcx))
}

pub fn is_doc_hidden(&self) -> bool {
Expand All @@ -875,6 +881,32 @@ impl Item {
}
}

struct AttrIterator<'a, 'tcx> {
item: &'a Item,
document_private: bool,
tcx: TyCtxt<'tcx>,
done: bool,
}

impl<'a, 'tcx> AttrIterator<'a, 'tcx> {
fn new(item: &'a Item, document_private: bool, tcx: TyCtxt<'tcx>) -> Self {
Self { item, document_private, tcx, done: false }
}
}

impl<'a, 'tcx> Iterator for AttrIterator<'a, 'tcx> {
type Item = String;

fn next(&mut self) -> Option<Self::Item> {
if self.done {
None
} else {
self.done = true;
self.item.adt_item_extra_attrs(self.tcx, self.document_private)
}
}
}

#[derive(Clone, Debug)]
pub(crate) enum ItemKind {
ExternCrateItem {
Expand Down
2 changes: 1 addition & 1 deletion src/librustdoc/json/conversions.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -40,7 +40,7 @@ impl JsonRenderer<'_> {
})
.collect();
let docs = item.opt_doc_value();
let attrs = item.attributes(self.tcx, self.cache(), true);
let attrs = item.attributes(self.tcx, self.cache(), true).collect::<Vec<_>>();
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@notriddle notriddle May 4, 2025

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Another potential memory-use improvement.

Suggested change
let attrs = item.attributes(self.tcx, self.cache(), true).collect::<Vec<_>>();
let attrs = item.attributes(self.tcx, self.cache(), true).collect::<ThinVec<_>>();

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@GuillaumeGomez GuillaumeGomez May 5, 2025

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This requires changing rustdoc-json-types so maybe in a follow-up. Let's see if the rest of your suggestions will work.

let span = item.span(self.tcx);
let visibility = item.visibility(self.tcx);
let clean::ItemInner { name, item_id, .. } = *item.inner;
Expand Down
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