From 91009ca8800e4dad1537c03ffc4e9363d3946ee6 Mon Sep 17 00:00:00 2001
From: ffccites <99155080+PDGGK@users.noreply.github.com>
Date: Wed, 12 Aug 2026 11:22:59 +1000
Subject: [PATCH] fix(services/upyun): do not panic when creating the service
 root

create_dir sliced the last byte off the absolute path to drop its
trailing slash:

    let path = build_abs_path(&self.root, path);
    let path = path[..path.len() - 1].to_string();

build_abs_path returns an empty string when the root is / and the path
is /, so path.len() - 1 underflows and the call panics with "attempt to
subtract with overflow" rather than returning a Result.

The root is reachable from the public API: Operator::create_dir only
rejects a path that does not end with /, and / does end with /, so
op.create_dir("/") on a default-rooted upyun operator panics inside the
library.

This was the only `len() - 1]` slice left in core/services; the sibling
services already use trim_end_matches('/') for this, which is total and
identical for a normalized path since normalize_path leaves exactly one
trailing slash.

Two unit tests. The root one panics against the previous expression;
the trailing-slash one passes either way, so it is a control rather
than a second copy of the same assertion.
---
 core/services/upyun/src/core.rs | 30 ++++++++++++++++++++++++++++--
 1 file changed, 28 insertions(+), 2 deletions(-)

diff --git a/core/services/upyun/src/core.rs b/core/services/upyun/src/core.rs
index 6a0aa6b65008..c7b928292e0a 100644
--- a/core/services/upyun/src/core.rs
+++ b/core/services/upyun/src/core.rs
@@ -68,6 +68,16 @@ pub struct UpyunCore {
     pub signer: UpyunSigner,
 }
 
+/// Build the folder key for a directory path, without its trailing slash.
+///
+/// `build_abs_path` returns an empty string for the root of a service whose root is `/`, so
+/// slicing off the last byte underflows there. `Operator::create_dir` only checks that the path
+/// ends with `/`, and `/` does, so the root reaches this code and a library call panics instead of
+/// returning an error. `trim_end_matches` is what the sibling services use and is total.
+fn folder_path(root: &str, path: &str) -> String {
+    build_abs_path(root, path).trim_end_matches('/').to_string()
+}
+
 impl Debug for UpyunCore {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         f.debug_struct("UpyunCore")
@@ -292,8 +302,7 @@ impl UpyunCore {
     }
 
     pub async fn create_dir(&self, ctx: &OperationContext, path: &str) -> Result<Response<Buffer>> {
-        let path = build_abs_path(&self.root, path);
-        let path = path[..path.len() - 1].to_string();
+        let path = folder_path(&self.root, path);
 
         let url = format!(
             "https://v0.api.upyun.com/{}/{}",
@@ -654,3 +663,20 @@ mod error {
 }
 
 pub(super) use error::*;
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn folder_path_handles_the_service_root() {
+        // build_abs_path yields "" here; the previous `path[..path.len() - 1]` underflowed.
+        assert_eq!(folder_path("/", "/"), "");
+    }
+
+    #[test]
+    fn folder_path_drops_the_trailing_slash() {
+        assert_eq!(folder_path("/", "a/b/"), "a/b");
+        assert_eq!(folder_path("/prefix/", "a/"), "prefix/a");
+    }
+}