2 files changed, 315 insertions, 0 deletions
diff --git a/src/tools/rust-analyzer/crates/paths/Cargo.toml b/src/tools/rust-analyzer/crates/paths/Cargo.toml
new file mode 100644
index 000000000..5e83de7d9
--- /dev/null
+++ b/src/tools/rust-analyzer/crates/paths/Cargo.toml
@@ -0,0 +1,16 @@
+[package]
+name = "paths"
+version = "0.0.0"
+description = "TBD"
+license = "MIT OR Apache-2.0"
+edition = "2021"
+rust-version = "1.57"
+
+[lib]
+doctest = false
+
+[dependencies]
+# Adding this dep sadly puts a lot of rust-analyzer crates after the
+# serde-derive crate. Even though we don't activate the derive feature here,
+# someone else in the crate graph certainly does!
+# serde = "1"
diff --git a/src/tools/rust-analyzer/crates/paths/src/lib.rs b/src/tools/rust-analyzer/crates/paths/src/lib.rs
new file mode 100644
index 000000000..025093f4a
--- /dev/null
+++ b/src/tools/rust-analyzer/crates/paths/src/lib.rs
@@ -0,0 +1,299 @@
+//! Thin wrappers around `std::path`, distinguishing between absolute and
+//! relative paths.
+
+#![warn(rust_2018_idioms, unused_lifetimes, semicolon_in_expressions_from_macros)]
+
+use std::{
+    borrow::Borrow,
+    ffi::OsStr,
+    ops,
+    path::{Component, Path, PathBuf},
+};
+
+/// Wrapper around an absolute [`PathBuf`].
+#[derive(Debug, Clone, Ord, PartialOrd, Eq, PartialEq, Hash)]
+pub struct AbsPathBuf(PathBuf);
+
+impl From<AbsPathBuf> for PathBuf {
+    fn from(AbsPathBuf(path_buf): AbsPathBuf) -> PathBuf {
+        path_buf
+    }
+}
+
+impl ops::Deref for AbsPathBuf {
+    type Target = AbsPath;
+    fn deref(&self) -> &AbsPath {
+        self.as_path()
+    }
+}
+
+impl AsRef<Path> for AbsPathBuf {
+    fn as_ref(&self) -> &Path {
+        self.0.as_path()
+    }
+}
+
+impl AsRef<AbsPath> for AbsPathBuf {
+    fn as_ref(&self) -> &AbsPath {
+        self.as_path()
+    }
+}
+
+impl Borrow<AbsPath> for AbsPathBuf {
+    fn borrow(&self) -> &AbsPath {
+        self.as_path()
+    }
+}
+
+impl TryFrom<PathBuf> for AbsPathBuf {
+    type Error = PathBuf;
+    fn try_from(path_buf: PathBuf) -> Result<AbsPathBuf, PathBuf> {
+        if !path_buf.is_absolute() {
+            return Err(path_buf);
+        }
+        Ok(AbsPathBuf(path_buf))
+    }
+}
+
+impl TryFrom<&str> for AbsPathBuf {
+    type Error = PathBuf;
+    fn try_from(path: &str) -> Result<AbsPathBuf, PathBuf> {
+        AbsPathBuf::try_from(PathBuf::from(path))
+    }
+}
+
+impl PartialEq<AbsPath> for AbsPathBuf {
+    fn eq(&self, other: &AbsPath) -> bool {
+        self.as_path() == other
+    }
+}
+
+impl AbsPathBuf {
+    /// Wrap the given absolute path in `AbsPathBuf`
+    ///
+    /// # Panics
+    ///
+    /// Panics if `path` is not absolute.
+    pub fn assert(path: PathBuf) -> AbsPathBuf {
+        AbsPathBuf::try_from(path)
+            .unwrap_or_else(|path| panic!("expected absolute path, got {}", path.display()))
+    }
+
+    /// Coerces to an `AbsPath` slice.
+    ///
+    /// Equivalent of [`PathBuf::as_path`] for `AbsPathBuf`.
+    pub fn as_path(&self) -> &AbsPath {
+        AbsPath::assert(self.0.as_path())
+    }
+
+    /// Equivalent of [`PathBuf::pop`] for `AbsPathBuf`.
+    ///
+    /// Note that this won't remove the root component, so `self` will still be
+    /// absolute.
+    pub fn pop(&mut self) -> bool {
+        self.0.pop()
+    }
+}
+
+/// Wrapper around an absolute [`Path`].
+#[derive(Debug, Ord, PartialOrd, Eq, PartialEq, Hash)]
+#[repr(transparent)]
+pub struct AbsPath(Path);
+
+impl AsRef<Path> for AbsPath {
+    fn as_ref(&self) -> &Path {
+        &self.0
+    }
+}
+
+impl<'a> TryFrom<&'a Path> for &'a AbsPath {
+    type Error = &'a Path;
+    fn try_from(path: &'a Path) -> Result<&'a AbsPath, &'a Path> {
+        if !path.is_absolute() {
+            return Err(path);
+        }
+        Ok(AbsPath::assert(path))
+    }
+}
+
+impl AbsPath {
+    /// Wrap the given absolute path in `AbsPath`
+    ///
+    /// # Panics
+    ///
+    /// Panics if `path` is not absolute.
+    pub fn assert(path: &Path) -> &AbsPath {
+        assert!(path.is_absolute());
+        unsafe { &*(path as *const Path as *const AbsPath) }
+    }
+
+    /// Equivalent of [`Path::parent`] for `AbsPath`.
+    pub fn parent(&self) -> Option<&AbsPath> {
+        self.0.parent().map(AbsPath::assert)
+    }
+
+    /// Equivalent of [`Path::join`] for `AbsPath`.
+    pub fn join(&self, path: impl AsRef<Path>) -> AbsPathBuf {
+        self.as_ref().join(path).try_into().unwrap()
+    }
+
+    /// Normalize the given path:
+    /// - Removes repeated separators: `/a//b` becomes `/a/b`
+    /// - Removes occurrences of `.` and resolves `..`.
+    /// - Removes trailing slashes: `/a/b/` becomes `/a/b`.
+    ///
+    /// # Example
+    /// ```
+    /// # use paths::AbsPathBuf;
+    /// let abs_path_buf = AbsPathBuf::assert("/a/../../b/.//c//".into());
+    /// let normalized = abs_path_buf.normalize();
+    /// assert_eq!(normalized, AbsPathBuf::assert("/b/c".into()));
+    /// ```
+    pub fn normalize(&self) -> AbsPathBuf {
+        AbsPathBuf(normalize_path(&self.0))
+    }
+
+    /// Equivalent of [`Path::to_path_buf`] for `AbsPath`.
+    pub fn to_path_buf(&self) -> AbsPathBuf {
+        AbsPathBuf::try_from(self.0.to_path_buf()).unwrap()
+    }
+
+    /// Equivalent of [`Path::strip_prefix`] for `AbsPath`.
+    ///
+    /// Returns a relative path.
+    pub fn strip_prefix(&self, base: &AbsPath) -> Option<&RelPath> {
+        self.0.strip_prefix(base).ok().map(RelPath::new_unchecked)
+    }
+    pub fn starts_with(&self, base: &AbsPath) -> bool {
+        self.0.starts_with(&base.0)
+    }
+    pub fn ends_with(&self, suffix: &RelPath) -> bool {
+        self.0.ends_with(&suffix.0)
+    }
+
+    // region:delegate-methods
+
+    // Note that we deliberately don't implement `Deref<Target = Path>` here.
+    //
+    // The problem with `Path` is that it directly exposes convenience IO-ing
+    // methods. For example, `Path::exists` delegates to `fs::metadata`.
+    //
+    // For `AbsPath`, we want to make sure that this is a POD type, and that all
+    // IO goes via `fs`. That way, it becomes easier to mock IO when we need it.
+
+    pub fn file_name(&self) -> Option<&OsStr> {
+        self.0.file_name()
+    }
+    pub fn extension(&self) -> Option<&OsStr> {
+        self.0.extension()
+    }
+    pub fn file_stem(&self) -> Option<&OsStr> {
+        self.0.file_stem()
+    }
+    pub fn as_os_str(&self) -> &OsStr {
+        self.0.as_os_str()
+    }
+    pub fn display(&self) -> std::path::Display<'_> {
+        self.0.display()
+    }
+    #[deprecated(note = "use std::fs::metadata().is_ok() instead")]
+    pub fn exists(&self) -> bool {
+        self.0.exists()
+    }
+    // endregion:delegate-methods
+}
+
+/// Wrapper around a relative [`PathBuf`].
+#[derive(Debug, Clone, Ord, PartialOrd, Eq, PartialEq, Hash)]
+pub struct RelPathBuf(PathBuf);
+
+impl From<RelPathBuf> for PathBuf {
+    fn from(RelPathBuf(path_buf): RelPathBuf) -> PathBuf {
+        path_buf
+    }
+}
+
+impl ops::Deref for RelPathBuf {
+    type Target = RelPath;
+    fn deref(&self) -> &RelPath {
+        self.as_path()
+    }
+}
+
+impl AsRef<Path> for RelPathBuf {
+    fn as_ref(&self) -> &Path {
+        self.0.as_path()
+    }
+}
+
+impl TryFrom<PathBuf> for RelPathBuf {
+    type Error = PathBuf;
+    fn try_from(path_buf: PathBuf) -> Result<RelPathBuf, PathBuf> {
+        if !path_buf.is_relative() {
+            return Err(path_buf);
+        }
+        Ok(RelPathBuf(path_buf))
+    }
+}
+
+impl TryFrom<&str> for RelPathBuf {
+    type Error = PathBuf;
+    fn try_from(path: &str) -> Result<RelPathBuf, PathBuf> {
+        RelPathBuf::try_from(PathBuf::from(path))
+    }
+}
+
+impl RelPathBuf {
+    /// Coerces to a `RelPath` slice.
+    ///
+    /// Equivalent of [`PathBuf::as_path`] for `RelPathBuf`.
+    pub fn as_path(&self) -> &RelPath {
+        RelPath::new_unchecked(self.0.as_path())
+    }
+}
+
+/// Wrapper around a relative [`Path`].
+#[derive(Debug, Ord, PartialOrd, Eq, PartialEq, Hash)]
+#[repr(transparent)]
+pub struct RelPath(Path);
+
+impl AsRef<Path> for RelPath {
+    fn as_ref(&self) -> &Path {
+        &self.0
+    }
+}
+
+impl RelPath {
+    /// Creates a new `RelPath` from `path`, without checking if it is relative.
+    pub fn new_unchecked(path: &Path) -> &RelPath {
+        unsafe { &*(path as *const Path as *const RelPath) }
+    }
+}
+
+/// Taken from <https://github.com/rust-lang/cargo/blob/79c769c3d7b4c2cf6a93781575b7f592ef974255/src/cargo/util/paths.rs#L60-L85>
+fn normalize_path(path: &Path) -> PathBuf {
+    let mut components = path.components().peekable();
+    let mut ret = if let Some(c @ Component::Prefix(..)) = components.peek().copied() {
+        components.next();
+        PathBuf::from(c.as_os_str())
+    } else {
+        PathBuf::new()
+    };
+
+    for component in components {
+        match component {
+            Component::Prefix(..) => unreachable!(),
+            Component::RootDir => {
+                ret.push(component.as_os_str());
+            }
+            Component::CurDir => {}
+            Component::ParentDir => {
+                ret.pop();
+            }
+            Component::Normal(c) => {
+                ret.push(c);
+            }
+        }
+    }
+    ret
+}