fix(settings): remove overrides set on a path before it became a symlink

Overrides are keyed by canonical path, so `rustup override unset --path`
resolved a symlink and removed the override of its target instead. An
override set on the path before it was turned into a symlink stayed
behind, with no way to remove it (rust-lang#1138).

`Settings::remove_override()` now first tries the key of the path
itself, i.e. its canonical parent joined with its file name, and only
falls back to the resolved path when there is no such override.

Author: cachebag

src/settings.rs

@@ -2,7 +2,7 @@ use std::{
     cell::RefCell,
     collections::BTreeMap,
     fmt,
-    path::{Path, PathBuf},
+    path::{Path, PathBuf, absolute},
     str::FromStr,
 };
 
@@ -113,6 +113,17 @@ impl Settings {
     }
 
     pub(crate) fn remove_override(&mut self, path: &Path) -> bool {
+        // `path_to_key()` resolves symlinks, but `path` might have only become a
+        // symlink after its override was set, leaving that override keyed by
+        // `path` itself. Remove it first rather than the override of the target.
+        let unresolved_key = absolute(path).ok().and_then(|abs_path| {
+            let parent = abs_path.parent()?.canonicalize().ok()?;
+            Some(parent.join(abs_path.file_name()?).display().to_string())
+        });
+        if unresolved_key.is_some_and(|key| self.overrides.remove(&key).is_some()) {
+            return true;
+        }
+
         let key = Self::path_to_key(path);
         self.overrides.remove(&key).is_some()
     }

tests/suite/cli_exact.rs

@@ -530,7 +530,7 @@ info: override toolchain for '[PATH]' removed
             .extend_redactions([("[OLD]", old), ("[NEW]", new)])
             .is_ok()
             .with_stdout(snapbox::str![[r#"
-[OLD]	nightly             
+[NEW]	nightly             
 
 "#]])
             .with_stderr(snapbox::str![[""]]);