Auto merge of #148660 - fmease:cross-crate-cfg, r=GuillaumeGomez

Encode cfg trace, not its early counterpart to fix cross-crate `doc(auto_cfg)`

Fixes #141301.

<details><summary>Rambling about <code>target_feature</code> which I didn't touch here</summary>

Regarding #141301 (comment) (`#[target_feature(enable = …)]` on inlined cross-crate re-exports), it has the same underlying cause (namely, we neither encode `target_feature` nor `AttributeKind::TargetFeature` in the crate metadata). However, I didn't make that change because I first want to experiment with querying `TyCtxt::codegen_fn_attrs` in rustdoc instead which already works cross-crate (and also use to it for reconstructing `no_mangle`, `export_name`, `link_section` to avoid encoding these attributes unnecessarily (basically reverting #144050) as suggested in #144004 (comment)).

</details>

r? GuillaumeGomez

Author: bors

compiler/rustc_feature/src/builtin_attrs.rs

@@ -425,15 +425,15 @@ pub static BUILTIN_ATTRIBUTES: &[BuiltinAttribute] = &[
             List: &["predicate"],
             "https://doc.rust-lang.org/reference/conditional-compilation.html#the-cfg-attribute"
         ),
-        DuplicatesOk, EncodeCrossCrate::Yes
+        DuplicatesOk, EncodeCrossCrate::No
     ),
     ungated!(
         cfg_attr, Normal,
         template!(
             List: &["predicate, attr1, attr2, ..."],
             "https://doc.rust-lang.org/reference/conditional-compilation.html#the-cfg_attr-attribute"
         ),
-        DuplicatesOk, EncodeCrossCrate::Yes
+        DuplicatesOk, EncodeCrossCrate::No
     ),
 
     // Testing:
@@ -1115,7 +1115,7 @@ pub static BUILTIN_ATTRIBUTES: &[BuiltinAttribute] = &[
     // can only be generated by the compiler.
     ungated!(
         cfg_trace, Normal, template!(Word /* irrelevant */), DuplicatesOk,
-        EncodeCrossCrate::No
+        EncodeCrossCrate::Yes
     ),
     ungated!(
         cfg_attr_trace, Normal, template!(Word /* irrelevant */), DuplicatesOk,

tests/rustdoc/doc_auto_cfg.rs

@@ -1,4 +1,4 @@
-// Test covering RFC 3631 features.
+// Basic tests covering RFC 3631 features.
 
 #![crate_name = "foo"]
 #![feature(doc_cfg)]

tests/rustdoc/inline_cross/auxiliary/doc-auto-cfg.rs

@@ -0,0 +1,11 @@
+//@ compile-flags: --cfg extension
+
+#[cfg(extension)]
+pub fn compute() {}
+
+pub struct Type;
+
+impl Type {
+    #[cfg(extension)]
+    pub fn transform(self) -> Self { self }
+}

tests/rustdoc/inline_cross/auxiliary/u_default_generic_args.rs

@@ -0,0 +1,53 @@
+// Test that `doc(auto_cfg)` works with inlined cross-crate re-exports.
+//@ compile-flags: --cfg feature="extra" --cfg feature="addon"
+
+#![feature(doc_cfg)]
+#![crate_name = "it"]
+
+//@ aux-build: doc-auto-cfg.rs
+extern crate doc_auto_cfg;
+
+// The cfg is on the reexported item.
+// issue: <https://github.com/rust-lang/rust/issues/141301>
+pub mod pre {
+    //@ has 'it/pre/index.html' '//*[@class="stab portability"]' 'extension'
+    //@ has 'it/pre/fn.compute.html' '//*[@class="stab portability"]' \
+    //      'Available on extension only.'
+    pub use doc_auto_cfg::*;
+
+    // Indeed, this reexport doesn't have a cfg badge!
+    // That's because this crate (`it`) wouldn't've compiled in the first place
+    // if `--cfg extension` wasn't passed when compiling the auxiliary crate
+    // contrary to the glob import above since `compute` wouldn't exist.
+    //
+    //@ !has 'it/pre/fn.calculate.html' '//*[@class="stab portability"]' \
+    //      'Available on extension only.'
+    pub use doc_auto_cfg::compute as calculate;
+
+    // FIXME(HtmlDocCk): Ideally I would've used the following XPath here:
+    // `*[@class="impl-items"][*[@id="method.transform"]]//*[@class="stab portability"]`
+    //
+    //@ has 'it/pre/struct.Kind.html' '//*[@id="method.transform"]' ''
+    //@ has - '//*[@class="impl-items"]//*[@class="stab portability"]' \
+    //        'Available on extension only.'
+    pub use doc_auto_cfg::Type as Kind;
+}
+
+// The cfg is on the reexport.
+pub mod post {
+    // issue: <https://github.com/rust-lang/rust/issues/113982>
+    //@ has 'it/post/index.html' '//*[@class="stab portability"]' 'extra'
+    //@ has - '//*[@class="stab portability"]' 'extra and extension'
+    //@ has 'it/post/struct.Type.html' '//*[@class="stab portability"]' \
+    //      'Available on crate feature extra only.'
+    //@ has 'it/post/fn.compute.html' '//*[@class="stab portability"]' \
+    //      'Available on crate feature extra and extension only.'
+    #[cfg(feature = "extra")]
+    pub use doc_auto_cfg::*;
+
+    //@ has 'it/post/index.html' '//*[@class="stab portability"]' 'addon'
+    //@ has 'it/post/struct.Addon.html' '//*[@class="stab portability"]' \
+    //      'Available on crate feature addon only.'
+    #[cfg(feature = "addon")]
+    pub use doc_auto_cfg::Type as Addon;
+}

tests/rustdoc/inline_cross/doc-auto-cfg.rs

@@ -1,4 +1,4 @@
-// This test ensures that non-glob reexports don't get their attributes merge with
+// This test ensures that non-glob reexports don't get their attributes merged with
 // the reexported item whereas glob reexports do with the `doc_auto_cfg` feature.
 
 #![crate_name = "foo"]