rustdoc: Output target feature information

src/librustdoc/json/mod.rs

@@ -121,6 +121,28 @@ impl<'tcx> JsonRenderer<'tcx> {
             Ok(())
         })
     }
+
+    pub(crate) fn target(&self) -> types::Target {
+        let sess = self.tcx.sess;
+
+        let globally_enabled_features: FxHashMap<&str, ()> =
+            sess.target_features.iter().map(|sym| (sym.as_str(), ())).collect();
+
+        types::Target {
+            target_features: sess
+                .target
+                .rust_target_features()
+                .into_iter()
+                .copied()
+                .map(|(name, stability, implied)| types::TargetFeature {
+                    name: name.into(),
+                    stable: matches!(stability, rustc_target::target_features::Stability::Stable),
+                    implies_features: implied.into_iter().copied().map(String::from).collect(),
+                    globally_enabled: globally_enabled_features.contains_key(name),
+                })
+                .collect(),
+        }
+    }
 }
 
 impl<'tcx> FormatRenderer<'tcx> for JsonRenderer<'tcx> {
@@ -288,6 +310,7 @@ impl<'tcx> FormatRenderer<'tcx> for JsonRenderer<'tcx> {
                     )
                 })
                 .collect(),
+            target: self.target(),
             format_version: types::FORMAT_VERSION,
         };
         if let Some(ref out_dir) = self.out_dir {

src/rustdoc-json-types/lib.rs

@@ -52,11 +52,35 @@ pub struct Crate {
     pub paths: HashMap<Id, ItemSummary>,
     /// Maps `crate_id` of items to a crate name and html_root_url if it exists.
     pub external_crates: HashMap<u32, ExternalCrate>,
+    /// Information about the target for which this documentation was generated
+    pub target: Target,
     /// A single version number to be used in the future when making backwards incompatible changes
     /// to the JSON output.
     pub format_version: u32,
 }
 
+/// Information about a target
+#[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize)]
+pub struct Target {
+    /// A list of `#[target_feature]` which exist for this target, along with their status in this
+    /// compiler session
+    pub target_features: Vec<TargetFeature>,
+}
+
+/// Information about a `#[target_feature]`
+#[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize)]
+pub struct TargetFeature {
+    /// The name of this feature
+    pub name: String,
+    /// Other feature(s) which are implied by this feature
+    pub implies_features: Vec<String>,
+    /// Whether this feature is stable
+    pub stable: bool,
+    /// Whether this feature is globally enabled for this target, for example, due to the
+    /// target's ABI requiring this feature, or due to compiler flags which enable it everywhere
+    pub globally_enabled: bool,
+}
+
 /// Metadata of a crate, either the same crate on which `rustdoc` was invoked, or its dependency.
 #[derive(Clone, Debug, PartialEq, Eq, Hash, Serialize, Deserialize)]
 pub struct ExternalCrate {

src/tools/jsondoclint/src/validator/tests.rs

@@ -42,6 +42,7 @@ fn errors_on_missing_links() {
         )]),
         paths: FxHashMap::default(),
         external_crates: FxHashMap::default(),
+        target: rustdoc_json_types::Target { target_features: vec![] },
         format_version: rustdoc_json_types::FORMAT_VERSION,
     };
 
@@ -112,6 +113,7 @@ fn errors_on_local_in_paths_and_not_index() {
             },
         )]),
         external_crates: FxHashMap::default(),
+        target: rustdoc_json_types::Target { target_features: vec![] },
         format_version: rustdoc_json_types::FORMAT_VERSION,
     };
 
@@ -216,6 +218,7 @@ fn errors_on_missing_path() {
             ItemSummary { crate_id: 0, path: vec!["foo".to_owned()], kind: ItemKind::Module },
         )]),
         external_crates: FxHashMap::default(),
+        target: rustdoc_json_types::Target { target_features: vec![] },
         format_version: rustdoc_json_types::FORMAT_VERSION,
     };
 
@@ -259,6 +262,7 @@ fn checks_local_crate_id_is_correct() {
         )]),
         paths: FxHashMap::default(),
         external_crates: FxHashMap::default(),
+        target: rustdoc_json_types::Target { target_features: vec![] },
         format_version: FORMAT_VERSION,
     };
     check(&krate, &[]);