fix more redirect loops in redirector handler

src/web/extractors/rustdoc.rs

@@ -20,6 +20,13 @@ use std::borrow::Cow;
 const INDEX_HTML: &str = "index.html";
 const FOLDER_AND_INDEX_HTML: &str = "/index.html";
 
+pub(crate) const ROOT_RUSTDOC_HTML_FILES: &[&str] = &[
+    "all.html",
+    "help.html",
+    "settings.html",
+    "scrape-examples-help.html",
+];
+
 #[derive(Clone, Debug, PartialEq)]
 pub(crate) enum PageKind {
     Rustdoc,
@@ -723,27 +730,38 @@ fn generate_rustdoc_path_for_url(
         && !path.is_empty()
         && path != INDEX_HTML
     {
-        if let Some(target_name) = target_name
-            && path == target_name
-        {
-            // Sometimes people add a path that is just the target name.
-            // This matches our `rustdoc_redirector_handler` route,
-            // without trailing slash (`/{name}/{version}/{target}`).
-            //
-            // Even though the rustdoc html handler would also be capable
-            // handling this input, we want to redirect to the trailing
-            // slash version (`/{name}/{version}/{target}/`),
-            // so they are separate.
-            format!("{}/", target_name)
-        } else {
+        // for none-elements paths we have to guarantee that we have a
+        // trailing slash, otherwise the rustdoc-url won't hit the html-handler and
+        // lead to redirect loops.
+        if path.contains('/') {
             // just use the given inner to start, if:
             // * it's not empty
             // * it's not just "index.html"
+            // * we have a slash in the path.
             path.to_string()
+        } else if ROOT_RUSTDOC_HTML_FILES.contains(&path) {
+            // special case: some files are at the root of the rustdoc output,
+            // without a trailing slash, and the routes are fine with that.
+            // e.g. `/help.html`, `/settings.html`, `/all.html`, ...
+            path.to_string()
+        } else if let Some(target_name) = target_name {
+            if target_name == path {
+                // when we have the target name as path, without a trailing slash,
+                // just add the slash.
+                format!("{}/", path)
+            } else {
+                // when someone just attaches some path to the URL, like
+                // `/{krate}/{version}/somefile.html`, we assume they meant
+                // `/{krate}/{version}/{target_name}/somefile.html`.
+                format!("{}/{}", target_name, path)
+            }
+        } else {
+            // fallback: just attach a slash and redirect.
+            format!("{}/", path)
         }
     } else if let Some(target_name) = target_name {
         // after having no usable given path, we generate one with the
-        // target name, if we have one.
+        // target name, if we have one/.
         format!("{}/", target_name)
     } else {
         // no usable given path:
@@ -1000,12 +1018,17 @@ mod tests {
     )]
     #[test_case(
         None, Some("something"), false,
-        None, "something", "something";
+        None, "something", "krate/something";
         "without trailing slash"
     )]
+    #[test_case(
+        None, Some("settings.html"), false,
+        None, "settings.html", "settings.html";
+        "without trailing slash, but known root name"
+    )]
     #[test_case(
         None, Some("/something"), false,
-        None, "something", "something";
+        None, "something", "krate/something";
         "leading slash is cut"
     )]
     #[test_case(
@@ -1027,7 +1050,7 @@ mod tests {
     )]
     #[test_case(
         None, Some(&format!("{DEFAULT_TARGET}/one")), false,
-        Some(DEFAULT_TARGET), "one", "one";
+        Some(DEFAULT_TARGET), "one", "krate/one";
         "target + one without trailing slash"
     )]
     #[test_case(
@@ -1073,7 +1096,7 @@ mod tests {
     )]
     #[test_case(
         Some(UNKNOWN_TARGET), None, false,
-        None, UNKNOWN_TARGET, UNKNOWN_TARGET;
+        None, UNKNOWN_TARGET, &format!("krate/{UNKNOWN_TARGET}");
         "unknown target without trailing slash"
     )]
     #[test_case(
@@ -1639,23 +1662,26 @@ mod tests {
         assert_eq!(params.rustdoc_url(), "/krate/latest/krate/");
     }
 
-    #[test_case(Some(PageKind::Rustdoc))]
-    #[test_case(None)]
-    fn test_only_target_name_without_slash(page_kind: Option<PageKind>) {
+    #[test_case("other_path.html", "/krate/latest/krate/other_path.html")]
+    #[test_case("other_path", "/krate/latest/krate/other_path"; "without .html")]
+    #[test_case("other_path.html", "/krate/latest/krate/other_path.html"; "with .html")]
+    #[test_case("settings.html", "/krate/latest/settings.html"; "static routes")]
+    #[test_case(KRATE, "/krate/latest/krate/"; "same as target name, without slash")]
+    fn test_redirect_some_odd_paths_we_saw(inner_path: &str, expected_url: &str) {
         // test for https://github.com/rust-lang/docs.rs/issues/2989
         let params = RustdocParams::new(KRATE)
-            .with_maybe_page_kind(page_kind)
-            .try_with_original_uri("/dummy/latest/dummy")
+            .with_page_kind(PageKind::Rustdoc)
+            .try_with_original_uri(format!("/{KRATE}/latest/{inner_path}"))
             .unwrap()
             .with_req_version(ReqVersion::Latest)
             .with_maybe_doc_target(None::<String>)
-            .with_inner_path(KRATE)
+            .with_inner_path(inner_path)
             .with_default_target(DEFAULT_TARGET)
             .with_target_name(KRATE)
             .with_doc_targets(TARGETS.iter().cloned());
 
         dbg!(&params);
 
-        assert_eq!(params.rustdoc_url(), "/krate/latest/krate/");
+        assert_eq!(params.rustdoc_url(), expected_url);
     }
 }

src/web/rustdoc.rs

@@ -34,7 +34,7 @@ use axum::{
     http::StatusCode,
     response::{IntoResponse, Response as AxumResponse},
 };
-use http::{HeaderValue, Uri, header};
+use http::{HeaderValue, Uri, header, uri::Authority};
 use serde::Deserialize;
 use std::{
     collections::HashMap,
@@ -219,6 +219,7 @@ pub(crate) async fn rustdoc_redirector_handler(
     let params = params.with_page_kind(PageKind::Rustdoc);
 
     fn redirect_to_doc(
+        original_uri: Option<&Uri>,
         url: EscapedURI,
         cache_policy: CachePolicy,
         path_in_crate: Option<&str>,
@@ -229,6 +230,19 @@ pub(crate) async fn rustdoc_redirector_handler(
             url
         };
 
+        if let Some(original_uri) = original_uri
+            && original_uri.path() == url.path()
+            && (url.authority().is_none()
+                || url.authority() == Some(&Authority::from_static("docs.rs")))
+        {
+            return Err(anyhow!(
+                "infinite redirect detected, \noriginal_uri = {}, redirect_url = {}",
+                original_uri,
+                url
+            )
+            .into());
+        }
+
         trace!(%url, ?cache_policy, path_in_crate, "redirect to doc");
         Ok(axum_cached_redirect(url, cache_policy)?)
     }
@@ -266,6 +280,7 @@ pub(crate) async fn rustdoc_redirector_handler(
         let target_uri =
             EscapedURI::from_uri(description.href.clone()).append_raw_query(original_query);
         return redirect_to_doc(
+            params.original_uri(),
             target_uri,
             CachePolicy::ForeverInCdnAndStaleInBrowser,
             path_in_crate.as_deref(),
@@ -329,6 +344,7 @@ pub(crate) async fn rustdoc_redirector_handler(
 
     if matched_release.rustdoc_status() {
         Ok(redirect_to_doc(
+            params.original_uri(),
             params.rustdoc_url().append_raw_query(original_query),
             if matched_release.is_latest_url() {
                 CachePolicy::ForeverInCdn
@@ -3345,7 +3361,9 @@ mod test {
     #[tokio::test(flavor = "multi_thread")]
     #[test_case("/dummy/"; "only krate")]
     #[test_case("/dummy/latest/"; "with version")]
-    #[test_case("/dummy/latest/dummy"; "full without trailing slash")]
+    #[test_case("/dummy/latest/dummy"; "target-name as path, without trailing slash")]
+    #[test_case("/dummy/latest/other_path"; "other path, without trailing slash")]
+    #[test_case("/dummy/latest/other_path.html"; "other html path, without trailing slash")]
     #[test_case("/dummy/latest/dummy/"; "final target")]
     async fn test_full_latest_url_without_trailing_slash(path: &str) -> Result<()> {
         // test for https://github.com/rust-lang/docs.rs/issues/2989