Support multiple crate versions in --extern-html-root-url

compiler/rustc_metadata/src/creader.rs

@@ -12,6 +12,7 @@ use rustc_data_structures::fx::FxHashSet;
 use rustc_data_structures::owned_slice::OwnedSlice;
 use rustc_data_structures::svh::Svh;
 use rustc_data_structures::sync::{self, FreezeReadGuard, FreezeWriteGuard};
+use rustc_data_structures::unord::UnordMap;
 use rustc_errors::DiagCtxtHandle;
 use rustc_expand::base::SyntaxExtension;
 use rustc_fs_util::try_canonicalize;
@@ -68,6 +69,9 @@ pub struct CStore {
     /// This crate has a `#[alloc_error_handler]` item.
     has_alloc_error_handler: bool,
 
+    /// Names that were used to load the crates via `extern crate` or paths.
+    resolved_externs: UnordMap<Symbol, CrateNum>,
+
     /// Unused externs of the crate
     unused_externs: Vec<Symbol>,
 }
@@ -268,6 +272,22 @@ impl CStore {
         self.metas[cnum] = Some(Box::new(data));
     }
 
+    /// Save the name used to resolve the extern crate in the local crate
+    ///
+    /// The name isn't always the crate's own name, because `sess.opts.externs` can assign it another name.
+    /// It's also not always the same as the `DefId`'s symbol due to renames `extern crate name as defid_name`.
+    pub(crate) fn set_resolved_extern_crate_name(&mut self, name: Symbol, extern_crate: CrateNum) {
+        self.resolved_externs.insert(name, extern_crate);
+    }
+
+    /// Crate resolved and loaded via the given extern name
+    /// (corresponds to names in `sess.opts.externs`)
+    ///
+    /// May be `None` if the crate wasn't used
+    pub fn resolved_extern_crate(&self, externs_name: Symbol) -> Option<CrateNum> {
+        self.resolved_externs.get(&externs_name).copied()
+    }
+
     pub(crate) fn iter_crate_data(&self) -> impl Iterator<Item = (CrateNum, &CrateMetadata)> {
         self.metas
             .iter_enumerated()
@@ -494,6 +514,7 @@ impl CStore {
             alloc_error_handler_kind: None,
             has_global_allocator: false,
             has_alloc_error_handler: false,
+            resolved_externs: UnordMap::default(),
             unused_externs: Vec::new(),
         }
     }
@@ -533,7 +554,7 @@ impl<'a, 'tcx> CrateLoader<'a, 'tcx> {
             // We're also sure to compare *paths*, not actual byte slices. The
             // `source` stores paths which are normalized which may be different
             // from the strings on the command line.
-            let source = self.cstore.get_crate_data(cnum).cdata.source();
+            let source = data.source();
             if let Some(entry) = self.sess.opts.externs.get(name.as_str()) {
                 // Only use `--extern crate_name=path` here, not `--extern crate_name`.
                 if let Some(mut files) = entry.files() {
@@ -1302,6 +1323,7 @@ impl<'a, 'tcx> CrateLoader<'a, 'tcx> {
                 let path_len = definitions.def_path(def_id).data.len();
                 self.cstore.update_extern_crate(
                     cnum,
+                    name,
                     ExternCrate {
                         src: ExternCrateSource::Extern(def_id.to_def_id()),
                         span: item.span,
@@ -1320,6 +1342,7 @@ impl<'a, 'tcx> CrateLoader<'a, 'tcx> {
 
         self.cstore.update_extern_crate(
             cnum,
+            name,
             ExternCrate {
                 src: ExternCrateSource::Path,
                 span,

compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs

@@ -630,14 +630,29 @@ impl CStore {
         }
     }
 
-    pub(crate) fn update_extern_crate(&mut self, cnum: CrateNum, extern_crate: ExternCrate) {
+    /// Track how an extern crate has been loaded
+    ///
+    /// * the `name` is for [`Self::set_resolved_extern_crate_name`]
+    /// * `extern_crate` is for diagnostics
+    pub(crate) fn update_extern_crate(
+        &mut self,
+        cnum: CrateNum,
+        name: Symbol,
+        extern_crate: ExternCrate,
+    ) {
+        debug_assert_eq!(extern_crate.dependency_of, LOCAL_CRATE);
+        self.set_resolved_extern_crate_name(name, cnum);
+        self.update_extern_crate_inner(cnum, extern_crate);
+    }
+
+    fn update_extern_crate_inner(&mut self, cnum: CrateNum, extern_crate: ExternCrate) {
         let cmeta = self.get_crate_data_mut(cnum);
         if cmeta.update_extern_crate(extern_crate) {
             // Propagate the extern crate info to dependencies if it was updated.
             let extern_crate = ExternCrate { dependency_of: cnum, ..extern_crate };
             let dependencies = mem::take(&mut cmeta.dependencies);
             for &dep_cnum in &dependencies {
-                self.update_extern_crate(dep_cnum, extern_crate);
+                self.update_extern_crate_inner(dep_cnum, extern_crate);
             }
             self.get_crate_data_mut(cnum).dependencies = dependencies;
         }

src/librustdoc/formats/cache.rs

@@ -3,6 +3,7 @@ use std::mem;
 use rustc_attr_data_structures::StabilityLevel;
 use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexMap, FxIndexSet};
 use rustc_hir::def_id::{CrateNum, DefId, DefIdMap, DefIdSet};
+use rustc_metadata::creader::CStore;
 use rustc_middle::ty::{self, TyCtxt};
 use rustc_span::Symbol;
 use tracing::debug;
@@ -158,18 +159,31 @@ impl Cache {
         assert!(cx.external_traits.is_empty());
         cx.cache.traits = mem::take(&mut krate.external_traits);
 
+        let render_options = &cx.render_options;
+        let extern_url_takes_precedence = render_options.extern_html_root_takes_precedence;
+        let dst = &render_options.output;
+
+        // Make `--extern-html-root-url` support the same names as `--extern` whenever possible
+        let cstore = CStore::from_tcx(tcx);
+        for (name, extern_url) in &render_options.extern_html_root_urls {
+            if let Some(crate_num) = cstore.resolved_extern_crate(Symbol::intern(name)) {
+                let e = ExternalCrate { crate_num };
+                let location = e.location(Some(extern_url), extern_url_takes_precedence, dst, tcx);
+                cx.cache.extern_locations.insert(e.crate_num, location);
+            }
+        }
+
         // Cache where all our extern crates are located
         // FIXME: this part is specific to HTML so it'd be nice to remove it from the common code
         for &crate_num in tcx.crates(()) {
             let e = ExternalCrate { crate_num };
 
             let name = e.name(tcx);
-            let render_options = &cx.render_options;
-            let extern_url = render_options.extern_html_root_urls.get(name.as_str()).map(|u| &**u);
-            let extern_url_takes_precedence = render_options.extern_html_root_takes_precedence;
-            let dst = &render_options.output;
-            let location = e.location(extern_url, extern_url_takes_precedence, dst, tcx);
-            cx.cache.extern_locations.insert(e.crate_num, location);
+            cx.cache.extern_locations.entry(e.crate_num).or_insert_with(|| {
+                let extern_url =
+                    render_options.extern_html_root_urls.get(name.as_str()).map(|u| &**u);
+                e.location(extern_url, extern_url_takes_precedence, dst, tcx)
+            });
             cx.cache.external_paths.insert(e.def_id(), (vec![name], ItemType::Module));
         }
 

tests/rustdoc/extern/extern-html-alias.rs

@@ -0,0 +1,8 @@
+//@ compile-flags:-Z unstable-options --extern-html-root-url extern_prelude_name=https://renamed.example.com  --extern-html-root-url empty=https://bad.invalid
+//@ aux-crate:extern_prelude_name=empty.rs
+
+extern crate extern_prelude_name as internal_ident_name;
+
+//@ has extern_html_alias/index.html
+//@ has - '//a/@href' 'https://renamed.example.com/empty/index.html'
+pub use internal_ident_name as yet_different_name;