Generate unstable docs with items under feature

Add the items to the autogenerated stubs
Make unstable-book-gen use the top stage instead of stage 0
Generate the full docs, only print and save optional notes

Author: albertlarsan68

Cargo.lock

@@ -5906,6 +5906,9 @@ name = "unstable-book-gen"
 version = "0.1.0"
 dependencies = [
  "num-traits",
+ "rustdoc-json-types",
+ "serde_json",
+ "syn",
  "tidy",
 ]
 

src/bootstrap/src/core/build_steps/doc.rs

@@ -965,6 +965,13 @@ impl Step for UnstableBookGen {
 
     fn run(self, builder: &Builder<'_>) {
         let target = self.target;
+        let host = builder.build.build;
+
+        builder.ensure(Std {
+            stage: builder.top_stage,
+            target: host,
+            format: DocumentationFormat::JSON,
+        });
 
         builder.info(&format!("Generating unstable book md files ({target})"));
         let out = builder.md_doc_out(target).join("unstable-book");
@@ -974,6 +981,7 @@ impl Step for UnstableBookGen {
         cmd.arg(builder.src.join("library"));
         cmd.arg(builder.src.join("compiler"));
         cmd.arg(builder.src.join("src"));
+        cmd.arg(builder.json_doc_out(host));
         cmd.arg(out);
 
         builder.run(&mut cmd);

src/bootstrap/src/tests/builder.rs

@@ -312,7 +312,7 @@ mod dist {
         // Make sure rustdoc is only built once.
         assert_eq!(
             first(cache.all::<tool::Rustdoc>()),
-            &[tool::Rustdoc { compiler: Compiler { host: a, stage: 2 } },]
+            &[tool::Rustdoc { compiler: Compiler { host: a, stage: 2 } }]
         );
     }
 
@@ -636,7 +636,7 @@ mod dist {
         // stage minus 1 if --stage is not 0. Very confusing!
         assert_eq!(
             first(builder.cache.all::<tool::Rustdoc>()),
-            &[tool::Rustdoc { compiler: Compiler { host: a, stage: 2 } },]
+            &[tool::Rustdoc { compiler: Compiler { host: a, stage: 2 } }]
         );
     }
 

src/doc/unstable-book/src/library-features/allocator-api.md

@@ -1,11 +1,3 @@
-# `allocator_api`
-
-The tracking issue for this feature is [#32838]
-
-[#32838]: https://github.com/rust-lang/rust/issues/32838
-
-------------------------
-
 Sometimes you want the memory for one collection to use a different
 allocator than the memory for another collection. In this case,
 replacing the global allocator is not a workable option. Instead,

src/doc/unstable-book/src/library-features/c-variadic.md

@@ -1,11 +1,3 @@
-# `c_variadic`
-
-The tracking issue for this feature is: [#44930]
-
-[#44930]: https://github.com/rust-lang/rust/issues/44930
-
-------------------------
-
 The `c_variadic` library feature exposes the `VaList` structure,
 Rust's analogue of C's `va_list` type.
 

src/doc/unstable-book/src/library-features/c-void-variant.md

@@ -1,11 +1,3 @@
-# `concat_idents`
-
-The tracking issue for this feature is: [#29599]
-
-[#29599]: https://github.com/rust-lang/rust/issues/29599
-
-------------------------
-
 The `concat_idents` feature adds a macro for concatenating multiple identifiers
 into one identifier.