rustdoc: Add support for local resources

src/librustdoc/formats/cache.rs

@@ -1,4 +1,5 @@
 use std::mem;
+use std::path::PathBuf;
 
 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
 use rustc_hir::def_id::{CrateNum, DefId, DefIdMap, DefIdSet};
@@ -121,6 +122,8 @@ pub(crate) struct Cache {
     pub(crate) intra_doc_links: FxHashMap<ItemId, Vec<clean::ItemLink>>,
     /// Cfg that have been hidden via #![doc(cfg_hide(...))]
     pub(crate) hidden_cfg: FxHashSet<clean::cfg::Cfg>,
+    /// Local resources that are copied into the rustdoc output directory.
+    pub(crate) local_resources: LocalResources,
 }
 
 /// This struct is used to wrap the `cache` and `tcx` in order to run `DocFolder`.
@@ -516,6 +519,33 @@ impl<'a, 'tcx> DocFolder for CacheBuilder<'a, 'tcx> {
     }
 }
 
+#[derive(Default)]
+pub(crate) struct LocalResources {
+    /// The key is the original location of the resource. The value is the new name.
+    pub(crate) resources_to_copy: FxHashMap<PathBuf, String>,
+    /// This will be used when generating the HTML, once everything is generated, we copy these
+    /// files into the static folder.
+    ///
+    /// The key is the depth and the value is hashmap where the key is the path of the resource in
+    /// the markdown and the value is the new path to the resources in the rustdoc output folder.
+    pub(crate) resources_correspondance: FxHashMap<usize, FxHashMap<String, String>>,
+    pub(crate) total_entries: usize,
+}
+
+impl LocalResources {
+    pub(crate) fn add_entry_at_depth(&mut self, depth: usize, key: String, value: String) {
+        if self
+            .resources_correspondance
+            .entry(depth)
+            .or_insert_with(FxHashMap::default)
+            .insert(key, value)
+            .is_none()
+        {
+            self.total_entries += 1;
+        }
+    }
+}
+
 pub(crate) struct OrphanImplItem {
     pub(crate) parent: DefId,
     pub(crate) item: clean::Item,

src/librustdoc/html/mod.rs

@@ -13,3 +13,5 @@ mod url_parts_builder;
 
 #[cfg(test)]
 mod tests;
+
+pub(crate) const LOCAL_RESOURCES_FOLDER_NAME: &str = "local_resources";

src/librustdoc/html/render/context.rs

@@ -129,6 +129,10 @@ pub(crate) struct SharedContext<'tcx> {
     pub(crate) call_locations: AllCallLocations,
 }
 
+pub(crate) fn root_path(depth: usize) -> String {
+    "../".repeat(depth)
+}
+
 impl SharedContext<'_> {
     pub(crate) fn ensure_dir(&self, dst: &Path) -> Result<(), Error> {
         let mut dirs = self.created_dirs.borrow_mut();
@@ -165,7 +169,7 @@ impl<'tcx> Context<'tcx> {
     /// String representation of how to get back to the root path of the 'doc/'
     /// folder in terms of a relative URL.
     pub(super) fn root_path(&self) -> String {
-        "../".repeat(self.current.len())
+        root_path(self.current.len())
     }
 
     fn render_item(&mut self, it: &clean::Item, is_module: bool) -> String {

src/librustdoc/passes/collect_local_resources.rs

@@ -0,0 +1,137 @@
+//! This file will go through all doc comments and retrieve local resources to then store them
+//! in the rustdoc output directory.
+
+use pulldown_cmark::{Event, Parser, Tag};
+
+use rustc_span::def_id::LOCAL_CRATE;
+use rustc_span::FileName;
+
+use crate::clean::{Crate, Item};
+use crate::core::DocContext;
+use crate::html::markdown::main_body_opts;
+use crate::html::render::root_path;
+use crate::html::LOCAL_RESOURCES_FOLDER_NAME;
+use crate::passes::Pass;
+use crate::visit::DocVisitor;
+
+use std::path::{Path, PathBuf};
+
+pub(crate) const COLLECT_LOCAL_RESOURCES: Pass = Pass {
+    name: "collect-local-resources",
+    run: collect_local_resources,
+    description: "resolves intra-doc links",
+};
+
+fn span_file_path(cx: &DocContext<'_>, item: &Item) -> Option<PathBuf> {
+    item.span(cx.tcx).and_then(|span| match span.filename(cx.sess()) {
+        FileName::Real(ref path) => Some(path.local_path_if_available().into()),
+        _ => None,
+    })
+}
+
+struct ResourcesCollector<'a, 'tcx> {
+    cx: &'a mut DocContext<'tcx>,
+    /// The depth is used to know how many "../" needs to be generated to get the original file
+    /// path.
+    depth: usize,
+}
+
+fn collect_local_resources(krate: Crate, cx: &mut DocContext<'_>) -> Crate {
+    let mut collector = ResourcesCollector { cx, depth: 1 };
+    collector.visit_crate(&krate);
+    krate
+}
+
+impl<'a, 'tcx> ResourcesCollector<'a, 'tcx> {
+    pub fn handle_event(
+        &mut self,
+        event: Event<'_>,
+        current_path: &mut Option<PathBuf>,
+        item: &Item,
+    ) {
+        if let Event::Start(Tag::Image(_, ref ori_path, _)) = event &&
+            !ori_path.starts_with("http://") &&
+            !ori_path.starts_with("https://")
+        {
+            let ori_path = ori_path.to_string();
+            if self.cx.cache.local_resources.resources_correspondance
+                .get(&self.depth)
+                .and_then(|entry| entry.get(&ori_path))
+                .is_some()
+            {
+                // We already have this entry so nothing to be done!
+                return;
+            }
+            if current_path.is_none() {
+                *current_path = span_file_path(self.cx, item);
+            }
+            let Some(current_path) = current_path else { return };
+
+            let path = match current_path.parent()
+                .unwrap_or_else(|| Path::new("."))
+                .join(&ori_path)
+                .canonicalize()
+            {
+                Ok(p) => p,
+                Err(_) => {
+                    self.cx.tcx.sess.struct_span_err(
+                        item.attr_span(self.cx.tcx),
+                        &format!("`{ori_path}`: No such file"),
+                    ).emit();
+                    return;
+                }
+            };
+
+            if !path.is_file() {
+                self.cx.tcx.sess.struct_span_err(
+                    item.attr_span(self.cx.tcx),
+                    &format!("`{ori_path}`: No such file (expanded into `{}`)", path.display()),
+                ).emit();
+                return;
+            }
+
+            // We now enter the file into the `resources_to_copy` in case it's not already in
+            // and then generate a path the file that we store into `resources_correspondance`
+            // with the `add_entry_at_depth` method.
+            let current_nb = self.cx.cache.local_resources.resources_to_copy.len();
+            let file_name = self.cx.cache.local_resources.resources_to_copy
+                .entry(path.clone())
+                .or_insert_with(|| {
+                    let extension = path.extension();
+                    let (extension, dot) = match extension.and_then(|e| e.to_str()) {
+                        Some(e) => (e, "."),
+                        None => ("", ""),
+                    };
+                    format!(
+                        "{current_nb}{}{dot}{extension}",
+                        self.cx.render_options.resource_suffix,
+                    )
+                });
+            let file = format!(
+                "{}{LOCAL_RESOURCES_FOLDER_NAME}/{}/{file_name}",
+                root_path(self.depth),
+                self.cx.tcx.crate_name(LOCAL_CRATE).as_str(),
+            );
+            self.cx.cache.local_resources.add_entry_at_depth(self.depth, ori_path, file);
+        }
+    }
+}
+
+impl<'a, 'tcx> DocVisitor for ResourcesCollector<'a, 'tcx> {
+    fn visit_item(&mut self, item: &Item) {
+        if let Some(md) = item.collapsed_doc_value() {
+            let mut current_path = None;
+            for event in Parser::new_ext(&md, main_body_opts()).into_iter() {
+                self.handle_event(event, &mut current_path, item);
+            }
+        }
+
+        if item.is_mod() && !item.is_crate() {
+            self.depth += 1;
+            self.visit_item_recur(item);
+            self.depth -= 1;
+        } else {
+            self.visit_item_recur(item)
+        }
+    }
+}

src/librustdoc/passes/mod.rs

@@ -27,6 +27,9 @@ pub(crate) use self::propagate_doc_cfg::PROPAGATE_DOC_CFG;
 pub(crate) mod collect_intra_doc_links;
 pub(crate) use self::collect_intra_doc_links::COLLECT_INTRA_DOC_LINKS;
 
+pub(crate) mod collect_local_resources;
+pub(crate) use self::collect_local_resources::COLLECT_LOCAL_RESOURCES;
+
 mod check_doc_test_visibility;
 pub(crate) use self::check_doc_test_visibility::CHECK_DOC_TEST_VISIBILITY;
 
@@ -77,6 +80,7 @@ pub(crate) const PASSES: &[Pass] = &[
     PROPAGATE_DOC_CFG,
     COLLECT_INTRA_DOC_LINKS,
     COLLECT_TRAIT_IMPLS,
+    COLLECT_LOCAL_RESOURCES,
     CALCULATE_DOC_COVERAGE,
     RUN_LINTS,
 ];
@@ -89,6 +93,7 @@ pub(crate) const DEFAULT_PASSES: &[ConditionalPass] = &[
     ConditionalPass::new(STRIP_PRIVATE, WhenNotDocumentPrivate),
     ConditionalPass::new(STRIP_PRIV_IMPORTS, WhenDocumentPrivate),
     ConditionalPass::always(COLLECT_INTRA_DOC_LINKS),
+    ConditionalPass::always(COLLECT_LOCAL_RESOURCES),
     ConditionalPass::always(PROPAGATE_DOC_CFG),
     ConditionalPass::always(RUN_LINTS),
 ];