Rollup merge of #84101 - jyn514:early-pass, r=Manishearth

rustdoc: Move crate loader to collect_intra_doc_links::early

This groups the similar code together, and also allows making most of collect_intra_doc_links private again.

This builds on https://github.com/rust-lang/rust/pull/84066, but it wouldn't be too hard to base it off master if you want this to land first.
Helps with https://github.com/rust-lang/rust/issues/83761.

r? manishearth

Fixes https://github.com/rust-lang/rust/issues/84046

6 files changed, 220 insertions, 133 deletions

diff --git a/src/librustdoc/core.rs b/src/librustdoc/core.rs
index c9fdaa50534..be7bff1a29c 100644
--- a/src/librustdoc/core.rs
+++ b/src/librustdoc/core.rs
@@ -5,8 +5,8 @@ use rustc_driver::abort_on_err;
 use rustc_errors::emitter::{Emitter, EmitterWriter};
 use rustc_errors::json::JsonEmitter;
 use rustc_feature::UnstableFeatures;
-use rustc_hir::def::{Namespace::TypeNS, Res};
-use rustc_hir::def_id::{CrateNum, DefId, DefIndex, LocalDefId, CRATE_DEF_INDEX, LOCAL_CRATE};
+use rustc_hir::def::Res;
+use rustc_hir::def_id::{CrateNum, DefId, DefIndex, LocalDefId, LOCAL_CRATE};
 use rustc_hir::HirId;
 use rustc_hir::{
     intravisit::{self, NestedVisitorMap, Visitor},
@@ -356,55 +356,7 @@ crate fn create_resolver<'a>(
     let (krate, resolver, _) = &*parts;
     let resolver = resolver.borrow().clone();
 
-    // Letting the resolver escape at the end of the function leads to inconsistencies between the
-    // crates the TyCtxt sees and the resolver sees (because the resolver could load more crates
-    // after escaping). Hopefully `IntraLinkCrateLoader` gets all the crates we need ...
-    struct IntraLinkCrateLoader {
-        current_mod: DefId,
-        resolver: Rc<RefCell<interface::BoxedResolver>>,
-    }
-    impl ast::visit::Visitor<'_> for IntraLinkCrateLoader {
-        fn visit_attribute(&mut self, attr: &ast::Attribute) {
-            use crate::html::markdown::{markdown_links, MarkdownLink};
-            use crate::passes::collect_intra_doc_links::Disambiguator;
-
-            if let Some(doc) = attr.doc_str() {
-                for MarkdownLink { link, .. } in markdown_links(&doc.as_str()) {
-                    // FIXME: this misses a *lot* of the preprocessing done in collect_intra_doc_links
-                    // I think most of it shouldn't be necessary since we only need the crate prefix?
-                    let path_str = match Disambiguator::from_str(&link) {
-                        Ok(x) => x.map_or(link.as_str(), |(_, p)| p),
-                        Err(_) => continue,
-                    };
-                    self.resolver.borrow_mut().access(|resolver| {
-                        let _ = resolver.resolve_str_path_error(
-                            attr.span,
-                            path_str,
-                            TypeNS,
-                            self.current_mod,
-                        );
-                    });
-                }
-            }
-            ast::visit::walk_attribute(self, attr);
-        }
-
-        fn visit_item(&mut self, item: &ast::Item) {
-            use rustc_ast_lowering::ResolverAstLowering;
-
-            if let ast::ItemKind::Mod(..) = item.kind {
-                let new_mod =
-                    self.resolver.borrow_mut().access(|resolver| resolver.local_def_id(item.id));
-                let old_mod = mem::replace(&mut self.current_mod, new_mod.to_def_id());
-                ast::visit::walk_item(self, item);
-                self.current_mod = old_mod;
-            } else {
-                ast::visit::walk_item(self, item);
-            }
-        }
-    }
-    let crate_id = LocalDefId { local_def_index: CRATE_DEF_INDEX }.to_def_id();
-    let mut loader = IntraLinkCrateLoader { current_mod: crate_id, resolver };
+    let mut loader = crate::passes::collect_intra_doc_links::IntraLinkCrateLoader::new(resolver);
     ast::visit::walk_crate(&mut loader, krate);
 
     loader.resolver
diff --git a/src/librustdoc/passes/collect_intra_doc_links.rs b/src/librustdoc/passes/collect_intra_doc_links.rs
index 4bc7544e33d..6342110adfe 100644
--- a/src/librustdoc/passes/collect_intra_doc_links.rs
+++ b/src/librustdoc/passes/collect_intra_doc_links.rs
@@ -39,13 +39,16 @@ use crate::passes::Pass;
 
 use super::span_of_attrs;
 
+mod early;
+crate use early::IntraLinkCrateLoader;
+
 crate const COLLECT_INTRA_DOC_LINKS: Pass = Pass {
     name: "collect-intra-doc-links",
     run: collect_intra_doc_links,
     description: "resolves intra-doc links",
 };
 
-crate fn collect_intra_doc_links(krate: Crate, cx: &mut DocContext<'_>) -> Crate {
+fn collect_intra_doc_links(krate: Crate, cx: &mut DocContext<'_>) -> Crate {
     LinkCollector {
         cx,
         mod_ids: Vec::new(),
@@ -892,6 +895,117 @@ impl<'a, 'tcx> DocFolder for LinkCollector<'a, 'tcx> {
     }
 }
 
+enum PreprocessingError<'a> {
+    Anchor(AnchorFailure),
+    Disambiguator(Range<usize>, String),
+    Resolution(ResolutionFailure<'a>, String, Option<Disambiguator>),
+}
+
+impl From<AnchorFailure> for PreprocessingError<'_> {
+    fn from(err: AnchorFailure) -> Self {
+        Self::Anchor(err)
+    }
+}
+
+struct PreprocessingInfo {
+    path_str: String,
+    disambiguator: Option<Disambiguator>,
+    extra_fragment: Option<String>,
+    link_text: String,
+}
+
+/// Returns:
+/// - `None` if the link should be ignored.
+/// - `Some(Err)` if the link should emit an error
+/// - `Some(Ok)` if the link is valid
+///
+/// `link_buffer` is needed for lifetime reasons; it will always be overwritten and the contents ignored.
+fn preprocess_link<'a>(
+    ori_link: &'a MarkdownLink,
+) -> Option<Result<PreprocessingInfo, PreprocessingError<'a>>> {
+    // [] is mostly likely not supposed to be a link
+    if ori_link.link.is_empty() {
+        return None;
+    }
+
+    // Bail early for real links.
+    if ori_link.link.contains('/') {
+        return None;
+    }
+
+    let stripped = ori_link.link.replace("`", "");
+    let mut parts = stripped.split('#');
+
+    let link = parts.next().unwrap();
+    if link.trim().is_empty() {
+        // This is an anchor to an element of the current page, nothing to do in here!
+        return None;
+    }
+    let extra_fragment = parts.next();
+    if parts.next().is_some() {
+        // A valid link can't have multiple #'s
+        return Some(Err(AnchorFailure::MultipleAnchors.into()));
+    }
+
+    // Parse and strip the disambiguator from the link, if present.
+    let (path_str, disambiguator) = match Disambiguator::from_str(&link) {
+        Ok(Some((d, path))) => (path.trim(), Some(d)),
+        Ok(None) => (link.trim(), None),
+        Err((err_msg, relative_range)) => {
+            // Only report error if we would not have ignored this link. See issue #83859.
+            if !should_ignore_link_with_disambiguators(link) {
+                let no_backticks_range = range_between_backticks(&ori_link);
+                let disambiguator_range = (no_backticks_range.start + relative_range.start)
+                    ..(no_backticks_range.start + relative_range.end);
+                return Some(Err(PreprocessingError::Disambiguator(disambiguator_range, err_msg)));
+            } else {
+                return None;
+            }
+        }
+    };
+
+    if should_ignore_link(path_str) {
+        return None;
+    }
+
+    // We stripped `()` and `!` when parsing the disambiguator.
+    // Add them back to be displayed, but not prefix disambiguators.
+    let link_text =
+        disambiguator.map(|d| d.display_for(path_str)).unwrap_or_else(|| path_str.to_owned());
+
+    // Strip generics from the path.
+    let path_str = if path_str.contains(['<', '>'].as_slice()) {
+        match strip_generics_from_path(&path_str) {
+            Ok(path) => path,
+            Err(err_kind) => {
+                debug!("link has malformed generics: {}", path_str);
+                return Some(Err(PreprocessingError::Resolution(
+                    err_kind,
+                    path_str.to_owned(),
+                    disambiguator,
+                )));
+            }
+        }
+    } else {
+        path_str.to_owned()
+    };
+
+    // Sanity check to make sure we don't have any angle brackets after stripping generics.
+    assert!(!path_str.contains(['<', '>'].as_slice()));
+
+    // The link is not an intra-doc link if it still contains spaces after stripping generics.
+    if path_str.contains(' ') {
+        return None;
+    }
+
+    Some(Ok(PreprocessingInfo {
+        path_str,
+        disambiguator,
+        extra_fragment: extra_fragment.map(String::from),
+        link_text,
+    }))
+}
+
 impl LinkCollector<'_, '_> {
     /// This is the entry point for resolving an intra-doc link.
     ///
@@ -907,16 +1021,6 @@ impl LinkCollector<'_, '_> {
     ) -> Option<ItemLink> {
         trace!("considering link '{}'", ori_link.link);
 
-        // Bail early for real links.
-        if ori_link.link.contains('/') {
-            return None;
-        }
-
-        // [] is mostly likely not supposed to be a link
-        if ori_link.link.is_empty() {
-            return None;
-        }
-
         let diag_info = DiagnosticInfo {
             item,
             dox,
@@ -924,47 +1028,29 @@ impl LinkCollector<'_, '_> {
             link_range: ori_link.range.clone(),
         };
 
-        let link = ori_link.link.replace("`", "");
-        let no_backticks_range = range_between_backticks(&ori_link);
-        let parts = link.split('#').collect::<Vec<_>>();
-        let (link, extra_fragment) = if parts.len() > 2 {
-            // A valid link can't have multiple #'s
-            anchor_failure(self.cx, diag_info, AnchorFailure::MultipleAnchors);
-            return None;
-        } else if parts.len() == 2 {
-            if parts[0].trim().is_empty() {
-                // This is an anchor to an element of the current page, nothing to do in here!
-                return None;
-            }
-            (parts[0], Some(parts[1].to_owned()))
-        } else {
-            (parts[0], None)
-        };
-
-        // Parse and strip the disambiguator from the link, if present.
-        let (mut path_str, disambiguator) = match Disambiguator::from_str(&link) {
-            Ok(Some((d, path))) => (path.trim(), Some(d)),
-            Ok(None) => (link.trim(), None),
-            Err((err_msg, relative_range)) => {
-                if !should_ignore_link_with_disambiguators(link) {
-                    // Only report error if we would not have ignored this link.
-                    // See issue #83859.
-                    let disambiguator_range = (no_backticks_range.start + relative_range.start)
-                        ..(no_backticks_range.start + relative_range.end);
-                    disambiguator_error(self.cx, diag_info, disambiguator_range, &err_msg);
+        let PreprocessingInfo { path_str, disambiguator, extra_fragment, link_text } =
+            match preprocess_link(&ori_link)? {
+                Ok(x) => x,
+                Err(err) => {
+                    match err {
+                        PreprocessingError::Anchor(err) => anchor_failure(self.cx, diag_info, err),
+                        PreprocessingError::Disambiguator(range, msg) => {
+                            disambiguator_error(self.cx, diag_info, range, &msg)
+                        }
+                        PreprocessingError::Resolution(err, path_str, disambiguator) => {
+                            resolution_failure(
+                                self,
+                                diag_info,
+                                &path_str,
+                                disambiguator,
+                                smallvec![err],
+                            );
+                        }
+                    }
+                    return None;
                 }
-                return None;
-            }
-        };
-
-        if should_ignore_link(path_str) {
-            return None;
-        }
-
-        // We stripped `()` and `!` when parsing the disambiguator.
-        // Add them back to be displayed, but not prefix disambiguators.
-        let link_text =
-            disambiguator.map(|d| d.display_for(path_str)).unwrap_or_else(|| path_str.to_owned());
+            };
+        let mut path_str = &*path_str;
 
         // In order to correctly resolve intra-doc links we need to
         // pick a base AST node to work from.  If the documentation for
@@ -1029,39 +1115,12 @@ impl LinkCollector<'_, '_> {
             module_id = DefId { krate, index: CRATE_DEF_INDEX };
         }
 
-        // Strip generics from the path.
-        let stripped_path_string;
-        if path_str.contains(['<', '>'].as_slice()) {
-            stripped_path_string = match strip_generics_from_path(path_str) {
-                Ok(path) => path,
-                Err(err_kind) => {
-                    debug!("link has malformed generics: {}", path_str);
-                    resolution_failure(
-                        self,
-                        diag_info,
-                        path_str,
-                        disambiguator,
-                        smallvec![err_kind],
-                    );
-                    return None;
-                }
-            };
-            path_str = &stripped_path_string;
-        }
-        // Sanity check to make sure we don't have any angle brackets after stripping generics.
-        assert!(!path_str.contains(['<', '>'].as_slice()));
-
-        // The link is not an intra-doc link if it still contains spaces after stripping generics.
-        if path_str.contains(' ') {
-            return None;
-        }
-
         let (mut res, mut fragment) = self.resolve_with_disambiguator_cached(
             ResolutionInfo {
                 module_id,
                 dis: disambiguator,
                 path_str: path_str.to_owned(),
-                extra_fragment,
+                extra_fragment: extra_fragment.map(String::from),
             },
             diag_info.clone(), // this struct should really be Copy, but Range is not :(
             matches!(ori_link.kind, LinkType::Reference | LinkType::Shortcut),
@@ -1438,7 +1497,7 @@ fn should_ignore_link(path_str: &str) -> bool {
 
 #[derive(Copy, Clone, Debug, PartialEq, Eq, Hash)]
 /// Disambiguators for a link.
-crate enum Disambiguator {
+enum Disambiguator {
     /// `prim@`
     ///
     /// This is buggy, see <https://github.com/rust-lang/rust/pull/77875#discussion_r503583103>
@@ -1467,7 +1526,7 @@ impl Disambiguator {
     /// This returns `Ok(Some(...))` if a disambiguator was found,
     /// `Ok(None)` if no disambiguator was found, or `Err(...)`
     /// if there was a problem with the disambiguator.
-    crate fn from_str(link: &str) -> Result<Option<(Self, &str)>, (String, Range<usize>)> {
+    fn from_str(link: &str) -> Result<Option<(Self, &str)>, (String, Range<usize>)> {
         use Disambiguator::{Kind, Namespace as NS, Primitive};
 
         if let Some(idx) = link.find('@') {
diff --git a/src/librustdoc/passes/collect_intra_doc_links/early.rs b/src/librustdoc/passes/collect_intra_doc_links/early.rs
new file mode 100644
index 00000000000..7cba2523d1a
--- /dev/null
+++ b/src/librustdoc/passes/collect_intra_doc_links/early.rs
@@ -0,0 +1,63 @@
+use rustc_ast as ast;
+use rustc_hir::def::Namespace::TypeNS;
+use rustc_hir::def_id::{DefId, LocalDefId, CRATE_DEF_INDEX};
+use rustc_interface::interface;
+
+use std::cell::RefCell;
+use std::mem;
+use std::rc::Rc;
+
+// Letting the resolver escape at the end of the function leads to inconsistencies between the
+// crates the TyCtxt sees and the resolver sees (because the resolver could load more crates
+// after escaping). Hopefully `IntraLinkCrateLoader` gets all the crates we need ...
+crate struct IntraLinkCrateLoader {
+    current_mod: DefId,
+    crate resolver: Rc<RefCell<interface::BoxedResolver>>,
+}
+
+impl IntraLinkCrateLoader {
+    crate fn new(resolver: Rc<RefCell<interface::BoxedResolver>>) -> Self {
+        let crate_id = LocalDefId { local_def_index: CRATE_DEF_INDEX }.to_def_id();
+        Self { current_mod: crate_id, resolver }
+    }
+}
+
+impl ast::visit::Visitor<'_> for IntraLinkCrateLoader {
+    fn visit_attribute(&mut self, attr: &ast::Attribute) {
+        use crate::html::markdown::markdown_links;
+        use crate::passes::collect_intra_doc_links::preprocess_link;
+
+        if let Some(doc) = attr.doc_str() {
+            for link in markdown_links(&doc.as_str()) {
+                let path_str = if let Some(Ok(x)) = preprocess_link(&link) {
+                    x.path_str
+                } else {
+                    continue;
+                };
+                self.resolver.borrow_mut().access(|resolver| {
+                    let _ = resolver.resolve_str_path_error(
+                        attr.span,
+                        &path_str,
+                        TypeNS,
+                        self.current_mod,
+                    );
+                });
+            }
+        }
+        ast::visit::walk_attribute(self, attr);
+    }
+
+    fn visit_item(&mut self, item: &ast::Item) {
+        use rustc_ast_lowering::ResolverAstLowering;
+
+        if let ast::ItemKind::Mod(..) = item.kind {
+            let new_mod =
+                self.resolver.borrow_mut().access(|resolver| resolver.local_def_id(item.id));
+            let old_mod = mem::replace(&mut self.current_mod, new_mod.to_def_id());
+            ast::visit::walk_item(self, item);
+            self.current_mod = old_mod;
+        } else {
+            ast::visit::walk_item(self, item);
+        }
+    }
+}
diff --git a/src/test/rustdoc/intra-doc/auxiliary/empty.rs b/src/test/rustdoc/intra-doc/auxiliary/empty.rs
new file mode 100644
index 00000000000..d11c69f812a
--- /dev/null
+++ b/src/test/rustdoc/intra-doc/auxiliary/empty.rs
@@ -0,0 +1 @@
+// intentionally empty
diff --git a/src/test/rustdoc/intra-doc/auxiliary/empty2.rs b/src/test/rustdoc/intra-doc/auxiliary/empty2.rs
new file mode 100644
index 00000000000..d11c69f812a
--- /dev/null
+++ b/src/test/rustdoc/intra-doc/auxiliary/empty2.rs
@@ -0,0 +1 @@
+// intentionally empty
diff --git a/src/test/rustdoc/intra-doc/extern-crate-only-used-in-link.rs b/src/test/rustdoc/intra-doc/extern-crate-only-used-in-link.rs
index 0964c79de06..5d8dcf8bc1d 100644
--- a/src/test/rustdoc/intra-doc/extern-crate-only-used-in-link.rs
+++ b/src/test/rustdoc/intra-doc/extern-crate-only-used-in-link.rs
@@ -1,8 +1,19 @@
+// This test is just a little cursed.
 // aux-build:issue-66159-1.rs
 // aux-crate:priv:issue_66159_1=issue-66159-1.rs
+// aux-build:empty.rs
+// aux-crate:priv:empty=empty.rs
+// aux-build:empty2.rs
+// aux-crate:priv:empty2=empty2.rs
 // build-aux-docs
-// compile-flags:-Z unstable-options
+// compile-flags:-Z unstable-options --edition 2018
 
 // @has extern_crate_only_used_in_link/index.html
 // @has - '//a[@href="../issue_66159_1/struct.Something.html"]' 'issue_66159_1::Something'
 //! [issue_66159_1::Something]
+
+// @has - '//a[@href="../empty/index.html"]' 'empty'
+//! [`empty`]
+
+// @has - '//a[@href="../empty2/index.html"]' 'empty2'
+//! [empty2<x>]