Automation roots: compare canonical components exactly

crates/engine/src/file_access.rs

@@ -10,7 +10,8 @@
 //!   folder, the rest of the path being plain names (`..` below a missing folder is refused, and so
 //!   is a link that leads nowhere).
 //! - The result must lie inside one of the roots of its kind, compared by whole components
-//!   (`/work2` isn't inside `/work`), without regard to case on Windows.
+//!   (`/work2` isn't inside `/work`), by the case the disk stores (links are resolved first, so a
+//!   differently cased spelling of a root still lands inside it).
 //! - Read and write access are separate: a root given alone grants only its own kind of access.
 //!
 //! Roots are in force on a thread inside [`confine`], and in the whole process after
@@ -266,24 +267,12 @@ fn resolve(path: &Path) -> Result<PathBuf, String> {
     }
 }
 
-/// Is `path` (resolved) `root` or inside it, component by component (without regard to case on
-/// Windows, whose file systems ignore it)?
+/// Is `path` (resolved) `root` or inside it, component by component? Both come from
+/// `canonicalize`, which gives the name's case as the disk stores it, so equal means the same
+/// folder; folding case would equate two folders on a case-sensitive Windows directory.
 fn inside(path: &Path, root: &Path) -> bool {
     let mut path = path.components();
-    root.components().all(|r| path.next().is_some_and(|p| same_component(p, r)))
-}
-
-fn same_component(a: Component, b: Component) -> bool {
-    if a == b {
-        return true;
-    }
-    if !cfg!(windows) {
-        return false;
-    }
-    match (a.as_os_str().to_str(), b.as_os_str().to_str()) {
-        (Some(a), Some(b)) => a.to_lowercase() == b.to_lowercase(),
-        _ => false,
-    }
+    root.components().all(|r| path.next().is_some_and(|p| p == r))
 }
 
 /// A Windows device name (`CON`, `NUL`, `COM1`… also with an extension), which names no file.
@@ -476,7 +465,7 @@ mod tests {
 
     #[cfg(windows)]
     #[test]
-    fn windows_ignores_case_and_refuses_devices() {
+    fn windows_resolves_case_and_refuses_devices() {
         let (base, roots) = folders("case");
         let upper = s(base.join("IN/a.scraft"));
         assert_eq!(roots.check(&upper, Access::Read), Ok(()), "{upper}");