From 854f619d6a023b15a8b5461a7923134f347b3bb6 Mon Sep 17 00:00:00 2001
From: Guillaume Gomez <guillaume1.gomez@gmail.com>
Date: Mon, 15 Dec 2025 14:36:18 +0100
Subject: [PATCH] Correctly encode doc attribute metadata

---
 .../rustc_hir/src/attrs/data_structures.rs    | 58 ++++++++++++++++++-
 compiler/rustc_metadata/src/rmeta/encoder.rs  | 10 +---
 2 files changed, 60 insertions(+), 8 deletions(-)

diff --git a/compiler/rustc_hir/src/attrs/data_structures.rs b/compiler/rustc_hir/src/attrs/data_structures.rs
index 34d78afca9b2c..5ebe121dd67ca 100644
--- a/compiler/rustc_hir/src/attrs/data_structures.rs
+++ b/compiler/rustc_hir/src/attrs/data_structures.rs
@@ -530,7 +530,7 @@ pub struct CfgHideShow {
     pub values: ThinVec<CfgInfo>,
 }
 
-#[derive(Clone, Debug, Default, HashStable_Generic, Encodable, Decodable, PrintAttribute)]
+#[derive(Clone, Debug, Default, HashStable_Generic, Decodable, PrintAttribute)]
 pub struct DocAttribute {
     pub aliases: FxIndexMap<Symbol, Span>,
     pub hidden: Option<Span>,
@@ -566,6 +566,62 @@ pub struct DocAttribute {
     pub no_crate_inject: Option<Span>,
 }
 
+impl<E: rustc_span::SpanEncoder> rustc_serialize::Encodable<E> for DocAttribute {
+    fn encode(&self, encoder: &mut E) {
+        let DocAttribute {
+            aliases,
+            hidden,
+            inline,
+            cfg,
+            auto_cfg,
+            auto_cfg_change,
+            fake_variadic,
+            keyword,
+            attribute,
+            masked,
+            notable_trait,
+            search_unbox,
+            html_favicon_url,
+            html_logo_url,
+            html_playground_url,
+            html_root_url,
+            html_no_source,
+            issue_tracker_base_url,
+            rust_logo,
+            test_attrs,
+            no_crate_inject,
+        } = self;
+        rustc_serialize::Encodable::<E>::encode(aliases, encoder);
+        rustc_serialize::Encodable::<E>::encode(hidden, encoder);
+
+        // FIXME: The `doc(inline)` attribute is never encoded, but is it actually the right thing
+        // to do? I suspect the condition was broken, should maybe instead not encode anything if we
+        // have `doc(no_inline)`.
+        let inline: ThinVec<_> =
+            inline.iter().filter(|(i, _)| *i != DocInline::Inline).cloned().collect();
+        rustc_serialize::Encodable::<E>::encode(&inline, encoder);
+
+        rustc_serialize::Encodable::<E>::encode(cfg, encoder);
+        rustc_serialize::Encodable::<E>::encode(auto_cfg, encoder);
+        rustc_serialize::Encodable::<E>::encode(auto_cfg_change, encoder);
+        rustc_serialize::Encodable::<E>::encode(fake_variadic, encoder);
+        rustc_serialize::Encodable::<E>::encode(keyword, encoder);
+        rustc_serialize::Encodable::<E>::encode(attribute, encoder);
+        rustc_serialize::Encodable::<E>::encode(masked, encoder);
+        rustc_serialize::Encodable::<E>::encode(notable_trait, encoder);
+        rustc_serialize::Encodable::<E>::encode(search_unbox, encoder);
+        rustc_serialize::Encodable::<E>::encode(html_favicon_url, encoder);
+        rustc_serialize::Encodable::<E>::encode(html_logo_url, encoder);
+        rustc_serialize::Encodable::<E>::encode(html_playground_url, encoder);
+        rustc_serialize::Encodable::<E>::encode(html_root_url, encoder);
+        rustc_serialize::Encodable::<E>::encode(html_no_source, encoder);
+        rustc_serialize::Encodable::<E>::encode(issue_tracker_base_url, encoder);
+        rustc_serialize::Encodable::<E>::encode(rust_logo, encoder);
+        rustc_serialize::Encodable::<E>::encode(test_attrs, encoder);
+        rustc_serialize::Encodable::<E>::encode(no_crate_inject, encoder);
+    }
+}
+
 /// Represents parsed *built-in* inert attributes.
 ///
 /// ## Overview
diff --git a/compiler/rustc_metadata/src/rmeta/encoder.rs b/compiler/rustc_metadata/src/rmeta/encoder.rs
index b15ed34fc3569..6abde26e7e6d1 100644
--- a/compiler/rustc_metadata/src/rmeta/encoder.rs
+++ b/compiler/rustc_metadata/src/rmeta/encoder.rs
@@ -879,13 +879,9 @@ fn analyze_attr(attr: &hir::Attribute, state: &mut AnalyzeAttrState<'_>) -> bool
             should_encode = true;
         }
     } else if let hir::Attribute::Parsed(AttributeKind::Doc(d)) = attr {
-        // If this is a `doc` attribute that doesn't have anything except maybe `inline` (as in
-        // `#[doc(inline)]`), then we can remove it. It won't be inlinable in downstream crates.
-        if d.inline.is_empty() {
-            should_encode = true;
-            if d.hidden.is_some() {
-                state.is_doc_hidden = true;
-            }
+        should_encode = true;
+        if d.hidden.is_some() {
+            state.is_doc_hidden = true;
         }
     } else if let &[sym::diagnostic, seg] = &*attr.path() {
         should_encode = rustc_feature::is_stable_diagnostic_attribute(seg, state.features);