Support absolute PATHS in x.py test [PATHS]

src/bootstrap/src/core/builder.rs

@@ -274,7 +274,7 @@ fn check(p: &TaskPath, needle: &Path, module: Kind) -> bool {
     /// This is used for `StepDescription::krate`, which passes all matching crates at once to
     /// `Step::make_run`, rather than calling it many times with a single crate.
     /// See `tests.rs` for examples.
-    fn intersection_removing_matches(&self, needles: &mut Vec<&Path>, module: Kind) -> PathSet {
+    fn intersection_removing_matches(&self, needles: &mut Vec<PathBuf>, module: Kind) -> PathSet {
         let mut check = |p| {
             for (i, n) in needles.iter().enumerate() {
                 let matched = Self::check(p, n, module);
@@ -346,7 +346,7 @@ pub fn assert_single_path(&self) -> &TaskPath {
     ),
 ];
 
-fn remap_paths(paths: &mut Vec<&Path>) {
+fn remap_paths(paths: &mut Vec<PathBuf>) {
     let mut remove = vec![];
     let mut add = vec![];
     for (i, path) in paths.iter().enumerate().filter_map(|(i, path)| path.to_str().map(|s| (i, s)))
@@ -355,7 +355,7 @@ fn remap_paths(paths: &mut Vec<&Path>) {
             // Remove leading and trailing slashes so `tests/` and `tests` are equivalent
             if path.trim_matches(std::path::is_separator) == search {
                 remove.push(i);
-                add.extend(replace.iter().map(Path::new));
+                add.extend(replace.iter().map(PathBuf::from));
                 break;
             }
         }
@@ -438,8 +438,25 @@ fn run(v: &[StepDescription], builder: &Builder<'_>, paths: &[PathBuf]) {
             }
         }
 
-        // strip CurDir prefix if present
+        // Attempt to resolve paths to be relative to the builder source directory.
-        let mut paths: Vec<_> = paths.iter().map(|p| p.strip_prefix(".").unwrap_or(p)).collect();
+        let mut paths: Vec<PathBuf> = paths
+            .iter()
+            .map(|p| {
+                // If the path does not exist, it may represent the name of a Step, such as `tidy` in `x test tidy`
+                if !p.exists() {
+                    return p.clone();
+                }
+
+                // Make the path absolute, strip the prefix, and convert to a PathBuf.
+                match std::path::absolute(p) {
+                    Ok(p) => p.strip_prefix(&builder.src).unwrap_or(&p).to_path_buf(),
+                    Err(e) => {
+                        eprintln!("ERROR: {:?}", e);
+                        panic!("Due to the above error, failed to resolve path: {:?}", p);
+                    }
+                }
+            })
+            .collect();
 
         remap_paths(&mut paths);
 
@@ -629,7 +646,7 @@ pub fn never(mut self) -> ShouldRun<'a> {
     /// (for now, just `all_krates` and `paths`, but we may want to add an `aliases` function in the future?)
     fn pathset_for_paths_removing_matches(
         &self,
-        paths: &mut Vec<&Path>,
+        paths: &mut Vec<PathBuf>,
         kind: Kind,
     ) -> Vec<PathSet> {
         let mut sets = vec![];

src/bootstrap/src/core/builder/tests.rs

@@ -122,11 +122,14 @@ fn test_intersection() {
         PathSet::Set(paths.into_iter().map(|p| TaskPath { path: p.into(), kind: None }).collect())
     };
     let library_set = set(&["library/core", "library/alloc", "library/std"]);
-    let mut command_paths =
+    let mut command_paths = vec![
-        vec![Path::new("library/core"), Path::new("library/alloc"), Path::new("library/stdarch")];
+        PathBuf::from("library/core"),
+        PathBuf::from("library/alloc"),
+        PathBuf::from("library/stdarch"),
+    ];
     let subset = library_set.intersection_removing_matches(&mut command_paths, Kind::Build);
     assert_eq!(subset, set(&["library/core", "library/alloc"]),);
-    assert_eq!(command_paths, vec![Path::new("library/stdarch")]);
+    assert_eq!(command_paths, vec![PathBuf::from("library/stdarch")]);
 }
 
 #[test]