Add --generate-redirect-map option to replace HTML redirection file with a unique JSON map

src/librustdoc/config.rs

@@ -265,6 +265,8 @@ crate struct RenderOptions {
     crate document_private: bool,
     /// Document items that have `doc(hidden)`.
     crate document_hidden: bool,
+    /// If `true`, generate a JSON file in the crate folder instead of HTML redirection files.
+    crate generate_redirect_map: bool,
     crate unstable_features: rustc_feature::UnstableFeatures,
 }
 
@@ -586,6 +588,7 @@ impl Options {
         let document_private = matches.opt_present("document-private-items");
         let document_hidden = matches.opt_present("document-hidden-items");
         let run_check = matches.opt_present("check");
+        let generate_redirect_map = matches.opt_present("generate-redirect-map");
 
         let (lint_opts, describe_lints, lint_cap) = get_cmd_lint_options(matches, error_format);
 
@@ -643,6 +646,7 @@ impl Options {
                 generate_search_filter,
                 document_private,
                 document_hidden,
+                generate_redirect_map,
                 unstable_features: rustc_feature::UnstableFeatures::from_environment(
                     crate_name.as_deref(),
                 ),

src/librustdoc/html/render/mod.rs

@@ -111,6 +111,10 @@ crate struct Context<'tcx> {
     /// real location of an item. This is used to allow external links to
     /// publicly reused items to redirect to the right location.
     crate render_redirect_pages: bool,
+    /// `None` by default, depends on the `generate-redirect-map` option flag. If this field is set
+    /// to `Some(...)`, it'll store redirections and then generate a JSON file at the top level of
+    /// the crate.
+    crate redirections: Option<Rc<RefCell<FxHashMap<String, String>>>>,
     /// The map used to ensure all generated 'id=' attributes are unique.
     id_map: Rc<RefCell<IdMap>>,
     /// Tracks section IDs for `Deref` targets so they match in both the main
@@ -405,6 +409,7 @@ impl<'tcx> FormatRenderer<'tcx> for Context<'tcx> {
             static_root_path,
             generate_search_filter,
             unstable_features,
+            generate_redirect_map,
             ..
         } = options;
 
@@ -510,6 +515,11 @@ impl<'tcx> FormatRenderer<'tcx> for Context<'tcx> {
             all: Rc::new(RefCell::new(AllTypes::new())),
             errors: Rc::new(receiver),
             cache: Rc::new(cache),
+            redirections: if generate_redirect_map {
+                Some(Rc::new(RefCell::new(FxHashMap::default())))
+            } else {
+                None
+            },
         };
 
         CURRENT_DEPTH.with(|s| s.set(0));
@@ -588,6 +598,15 @@ impl<'tcx> FormatRenderer<'tcx> for Context<'tcx> {
             &style_files,
         );
         self.shared.fs.write(&settings_file, v.as_bytes())?;
+        if let Some(redirections) = self.redirections.take() {
+            if !redirections.borrow().is_empty() {
+                let redirect_map_path =
+                    self.dst.join(&*krate.name.as_str()).join("redirect-map.json");
+                let paths = serde_json::to_string(&*redirections.borrow()).unwrap();
+                self.shared.ensure_dir(&self.dst.join(&*krate.name.as_str()))?;
+                self.shared.fs.write(&redirect_map_path, paths.as_bytes())?;
+            }
+        }
 
         // Flush pending errors.
         Arc::get_mut(&mut self.shared).unwrap().fs.close();
@@ -664,9 +683,9 @@ impl<'tcx> FormatRenderer<'tcx> for Context<'tcx> {
         if !buf.is_empty() {
             let name = item.name.as_ref().unwrap();
             let item_type = item.type_();
-            let file_name = &item_path(item_type, &name.as_str());
+            let file_name = item_path(item_type, &name.as_str());
             self.shared.ensure_dir(&self.dst)?;
-            let joint_dst = self.dst.join(file_name);
+            let joint_dst = self.dst.join(&file_name);
             self.shared.fs.write(&joint_dst, buf.as_bytes())?;
 
             if !self.render_redirect_pages {
@@ -676,11 +695,19 @@ impl<'tcx> FormatRenderer<'tcx> for Context<'tcx> {
             // to the new one (without).
             if item_type == ItemType::Macro {
                 let redir_name = format!("{}.{}!.html", item_type, name);
+                if let Some(ref redirections) = self.redirections {
+                    let crate_name = &self.shared.layout.krate;
+                    redirections.borrow_mut().insert(
+                        format!("{}/{}", crate_name, redir_name),
+                        format!("{}/{}", crate_name, file_name),
+                    );
+                } else {
+                    let v = layout::redirect(&file_name);
                     let redir_dst = self.dst.join(redir_name);
-                let v = layout::redirect(file_name);
                     self.shared.fs.write(&redir_dst, v.as_bytes())?;
                 }
             }
+        }
         Ok(())
     }
 
@@ -1588,19 +1615,29 @@ impl Context<'_> {
                 &self.shared.style_files,
             )
         } else {
-            let mut url = self.root_path();
             if let Some(&(ref names, ty)) = self.cache.paths.get(&it.def_id) {
+                let mut path = String::new();
                 for name in &names[..names.len() - 1] {
-                    url.push_str(name);
+                    path.push_str(name);
-                    url.push('/');
+                    path.push('/');
+                }
+                path.push_str(&item_path(ty, names.last().unwrap()));
+                match self.redirections {
+                    Some(ref redirections) => {
+                        let mut current_path = String::new();
+                        for name in &self.current {
+                            current_path.push_str(name);
+                            current_path.push('/');
+                        }
+                        current_path.push_str(&item_path(ty, names.last().unwrap()));
+                        redirections.borrow_mut().insert(current_path, path);
+                    }
+                    None => return layout::redirect(&format!("{}{}", self.root_path(), path)),
+                }
             }
-                url.push_str(&item_path(ty, names.last().unwrap()));
-                layout::redirect(&url)
-            } else {
             String::new()
         }
     }
-    }
 
     /// Construct a map of items shown in the sidebar to a plain-text summary of their docs.
     fn build_sidebar_items(&self, m: &clean::Module) -> BTreeMap<String, Vec<NameDoc>> {

src/librustdoc/lib.rs

@@ -423,6 +423,13 @@ fn opts() -> Vec<RustcOptGroup> {
             o.optopt("", "test-builder", "The rustc-like binary to use as the test builder", "PATH")
         }),
         unstable("check", |o| o.optflag("", "check", "Run rustdoc checks")),
+        unstable("generate-redirect-map", |o| {
+            o.optflag(
+                "",
+                "generate-redirect-map",
+                "Generate JSON file at the top level instead of generating HTML redirection files",
+            )
+        }),
     ]
 }