admin::render_readmes: Support out of order tar files

Achieves this by pulling the entire tar file into
memory in the form of a hashmap. Then we can look for
the files as needed.

Before, we would stream the pkg response from the server
and un-tar it on the fly, but this behavior is incorrect
if the Cargo.toml isn't at the beginning of the archive.

Could imagine this might be problematic if the entire
archive won't fit in memory - but that seems unlikely?
We could mitigate by limiting to certain file types, but
we won't know what type the README will be.

Added a test to for this case - the test fails
before this change and passes with this change

src/admin/render_readmes.rs

@@ -4,7 +4,7 @@ use crate::{
     schema::{crates, readme_renderings, versions},
     uploaders::Uploader,
 };
-use std::{io::Read, path::Path, sync::Arc, thread};
+use std::{collections::HashMap, ffi::OsString, io::Read, sync::Arc, thread};
 
 use cargo_registry_markdown::text_to_html;
 use chrono::{TimeZone, Utc};
@@ -196,16 +196,28 @@ fn get_readme(
     render_pkg_readme(archive, &pkg_name)
 }
 
-fn render_pkg_readme<R: Read>(mut archive: Archive<R>, pkg_name: &str) -> Option<String> {
-    let mut entries = archive
+fn render_pkg_readme<R: Read>(mut pkg: Archive<R>, pkg_name: &str) -> Option<String> {
+    // Pulls the entire archive into memory - since we need to access files
+    // within the archive potentially out of order (first Cargo.toml, then README)
+    let entries: HashMap<_, _> = pkg
         .entries()
-        .unwrap_or_else(|_| panic!("[{}] Invalid tar archive entries", pkg_name));
+        .unwrap_or_else(|_| panic!("[{}] Invalid tar archive entries", pkg_name))
+        .filter_map(|e| {
+            let mut file = e.ok()?;
+            let path = file.path().ok()?.as_os_str().to_owned();
+            let mut contents = String::new();
+            file.read_to_string(&mut contents)
+                .unwrap_or_else(|_| panic!("[{}] Couldn't read file contents", pkg_name));
+            Some((path, contents))
+        })
+        .collect();
 
     let manifest: Manifest = {
         let path = format!("{}/Cargo.toml", pkg_name);
-        let contents = find_file_by_path(&mut entries, Path::new(&path), pkg_name)
+        let contents = entries
+            .get(&OsString::from(path))
             .unwrap_or_else(|| panic!("[{}] couldn't open file: Cargo.toml", pkg_name));
-        toml::from_str(&contents)
+        toml::from_str(contents)
             .unwrap_or_else(|_| panic!("[{}] Syntax error in manifest file", pkg_name))
     };
 
@@ -216,9 +228,9 @@ fn render_pkg_readme<R: Read>(mut archive: Archive<R>, pkg_name: &str) -> Option
             .clone()
             .unwrap_or_else(|| "README.md".into());
         let path = format!("{}/{}", pkg_name, readme_path);
-        let contents = find_file_by_path(&mut entries, Path::new(&path), pkg_name)?;
+        let contents = entries.get(&OsString::from(path))?;
         text_to_html(
-            &contents,
+            contents,
             &readme_path,
             manifest.package.repository.as_deref(),
         )
@@ -237,31 +249,6 @@ fn render_pkg_readme<R: Read>(mut archive: Archive<R>, pkg_name: &str) -> Option
     }
 }
 
-/// Search an entry by its path in a Tar archive.
-fn find_file_by_path<R: Read>(
-    entries: &mut tar::Entries<'_, R>,
-    path: &Path,
-    pkg_name: &str,
-) -> Option<String> {
-    let mut file = entries
-        .find(|entry| match *entry {
-            Err(_) => false,
-            Ok(ref file) => {
-                let filepath = match file.path() {
-                    Ok(p) => p,
-                    Err(_) => return false,
-                };
-                filepath == path
-            }
-        })?
-        .unwrap_or_else(|_| panic!("[{}] file is not present: {}", pkg_name, path.display()));
-
-    let mut contents = String::new();
-    file.read_to_string(&mut contents)
-        .unwrap_or_else(|_| panic!("[{}] Couldn't read file contents", pkg_name));
-    Some(contents)
-}
-
 #[cfg(test)]
 mod tests {
     use std::io::Write;
@@ -325,6 +312,24 @@ readme = "README.md"
         assert!(result.contains("readme"))
     }
 
+    #[test]
+    fn test_render_pkg_readme_tar_order_backward() {
+        let mut pkg = tar::Builder::new(vec![]);
+        add_file(&mut pkg, "foo-0.0.1/README.md", b"readme");
+        add_file(
+            &mut pkg,
+            "foo-0.0.1/Cargo.toml",
+            br#"
+[package]
+readme = "README.md"
+"#,
+        );
+        let serialized_archive = pkg.into_inner().unwrap();
+        let result =
+            render_pkg_readme(tar::Archive::new(&*serialized_archive), "foo-0.0.1").unwrap();
+        assert!(result.contains("readme"))
+    }
+
     #[test]
     fn test_render_pkg_readme_w_link() {
         let mut pkg = tar::Builder::new(vec![]);