5 files changed, 117 insertions, 2 deletions

diff --git a/crates/vfs/src/file_set.rs b/crates/vfs/src/file_set.rs
index 348b6dbfd..0a4590c8d 100644
--- a/crates/vfs/src/file_set.rs
+++ b/crates/vfs/src/file_set.rs
@@ -83,7 +83,12 @@ impl fmt::Debug for FileSet {
 /// ```
 #[derive(Debug)]
 pub struct FileSetConfig {
+    /// Number of sets that `self` can partition a [`Vfs`] into.
+    ///
+    /// This should be the number of sets in `self.map` + 1 for files that don't fit in any
+    /// defined set.
     n_file_sets: usize,
+    /// Map from encoded paths to the set they belong to.
     map: fst::Map<Vec<u8>>,
 }
 
@@ -111,9 +116,15 @@ impl FileSetConfig {
         }
         res
     }
+
+    /// Number of sets that `self` can partition a [`Vfs`] into.
     fn len(&self) -> usize {
         self.n_file_sets
     }
+
+    /// Returns the set index for the given `path`.
+    ///
+    /// `scratch_space` is used as a buffer and will be entirely replaced.
     fn classify(&self, path: &VfsPath, scratch_space: &mut Vec<u8>) -> usize {
         scratch_space.clear();
         path.encode(scratch_space);
@@ -169,11 +180,15 @@ impl FileSetConfigBuilder {
     }
 }
 
+/// Implements [`fst::Automaton`]
+///
+/// It will match if `prefix_of` is a prefix of the given data.
 struct PrefixOf<'a> {
     prefix_of: &'a [u8],
 }
 
 impl<'a> PrefixOf<'a> {
+    /// Creates a new `PrefixOf` from the given slice.
     fn new(prefix_of: &'a [u8]) -> Self {
         Self { prefix_of }
     }
diff --git a/crates/vfs/src/lib.rs b/crates/vfs/src/lib.rs
index bae2c6118..e075d752b 100644
--- a/crates/vfs/src/lib.rs
+++ b/crates/vfs/src/lib.rs
@@ -176,6 +176,14 @@ impl Vfs {
     pub fn take_changes(&mut self) -> Vec<ChangedFile> {
         mem::take(&mut self.changes)
     }
+
+    /// Returns the id associated with `path`
+    ///
+    /// - If `path` does not exists in the `Vfs`, allocate a new id for it, associated with a
+    /// deleted file;
+    /// - Else, returns `path`'s id.
+    ///
+    /// Does not record a change.
     fn alloc_file_id(&mut self, path: VfsPath) -> FileId {
         let file_id = self.interner.intern(path);
         let idx = file_id.0 as usize;
@@ -183,9 +191,21 @@ impl Vfs {
         self.data.resize_with(len, || None);
         file_id
     }
+
+    /// Returns the content associated with the given `file_id`.
+    ///
+    /// # Panics
+    ///
+    /// Panics if no file is associated to that id.
     fn get(&self, file_id: FileId) -> &Option<Vec<u8>> {
         &self.data[file_id.0 as usize]
     }
+
+    /// Mutably returns the content associated with the given `file_id`.
+    ///
+    /// # Panics
+    ///
+    /// Panics if no file is associated to that id.
     fn get_mut(&mut self, file_id: FileId) -> &mut Option<Vec<u8>> {
         &mut self.data[file_id.0 as usize]
     }
diff --git a/crates/vfs/src/loader.rs b/crates/vfs/src/loader.rs
index 399015043..d3bdae562 100644
--- a/crates/vfs/src/loader.rs
+++ b/crates/vfs/src/loader.rs
@@ -147,6 +147,13 @@ impl Directories {
     pub fn contains_dir(&self, path: &AbsPath) -> bool {
         self.includes_path(path)
     }
+
+    /// Returns `true` if `path` is included in `self`.
+    ///
+    /// It is included if
+    ///   - An element in `self.include` is a prefix of `path`.
+    ///   - This path is longer than any element in `self.exclude` that is a prefix
+    ///     of `path`. In case of equality, exclusion wins.
     fn includes_path(&self, path: &AbsPath) -> bool {
         let mut include: Option<&AbsPathBuf> = None;
         for incl in &self.include {
@@ -170,6 +177,14 @@ impl Directories {
     }
 }
 
+/// Returns :
+/// ```text
+/// Directories {
+///     extensions: ["rs"],
+///     include: [base],
+///     exclude: [base/<exclude>],
+/// }
+/// ```
 fn dirs(base: AbsPathBuf, exclude: &[&str]) -> Directories {
     let exclude = exclude.iter().map(|it| base.join(it)).collect::<Vec<_>>();
     Directories { extensions: vec!["rs".to_string()], include: vec![base], exclude }
diff --git a/crates/vfs/src/path_interner.rs b/crates/vfs/src/path_interner.rs
index 4f70d61e8..2189e5e25 100644
--- a/crates/vfs/src/path_interner.rs
+++ b/crates/vfs/src/path_interner.rs
@@ -5,6 +5,7 @@ use rustc_hash::FxHashMap;
 
 use crate::{FileId, VfsPath};
 
+/// Structure to map between [`VfsPath`] and [`FileId`].
 #[derive(Default)]
 pub(crate) struct PathInterner {
     map: FxHashMap<VfsPath, FileId>,
@@ -12,9 +13,17 @@ pub(crate) struct PathInterner {
 }
 
 impl PathInterner {
+    /// Get the id corresponding to `path`.
+    ///
+    /// If `path` does not exists in `self`, returns [`None`].
     pub(crate) fn get(&self, path: &VfsPath) -> Option<FileId> {
         self.map.get(path).copied()
     }
+
+    /// Insert `path` in `self`.
+    ///
+    /// - If `path` already exists in `self`, returns its associated id;
+    /// - Else, returns a newly allocated id.
     pub(crate) fn intern(&mut self, path: VfsPath) -> FileId {
         if let Some(id) = self.get(&path) {
             return id;
@@ -25,6 +34,11 @@ impl PathInterner {
         id
     }
 
+    /// Returns the path corresponding to `id`.
+    ///
+    /// # Panics
+    ///
+    /// Panics if `id` does not exists in `self`.
     pub(crate) fn lookup(&self, id: FileId) -> &VfsPath {
         &self.vec[id.0 as usize]
     }
diff --git a/crates/vfs/src/vfs_path.rs b/crates/vfs/src/vfs_path.rs
index 74b6333e2..2b3d7fd84 100644
--- a/crates/vfs/src/vfs_path.rs
+++ b/crates/vfs/src/vfs_path.rs
@@ -102,7 +102,14 @@ impl VfsPath {
         }
     }
 
-    // Don't make this `pub`
+    /// **Don't make this `pub`**
+    ///
+    /// Encode the path in the given buffer.
+    ///
+    /// The encoding will be `0` if [`AbsPathBuf`], `1` if [`VirtualPath`], followed
+    /// by `self`'s representation.
+    ///
+    /// Note that this encoding is dependent on the operating system.
     pub(crate) fn encode(&self, buf: &mut Vec<u8>) {
         let tag = match &self.0 {
             VfsPathRepr::PathBuf(_) => 0,
@@ -259,6 +266,7 @@ mod windows_paths {
     }
 }
 
+/// Internal, private representation of [`VfsPath`].
 #[derive(Clone, Ord, PartialOrd, Eq, PartialEq, Hash)]
 enum VfsPathRepr {
     PathBuf(AbsPathBuf),
@@ -295,13 +303,34 @@ impl fmt::Debug for VfsPathRepr {
     }
 }
 
+/// `/`-separated virtual path.
+///
+/// This is used to describe files that do not reside on the file system.
 #[derive(Debug, Clone, Ord, PartialOrd, Eq, PartialEq, Hash)]
 struct VirtualPath(String);
 
 impl VirtualPath {
+    /// Returns `true` if `other` is a prefix of `self` (as strings).
     fn starts_with(&self, other: &VirtualPath) -> bool {
         self.0.starts_with(&other.0)
     }
+
+    /// Remove the last component of `self`.
+    ///
+    /// This will find the last `'/'` in `self`, and remove everything after it,
+    /// including the `'/'`.
+    ///
+    /// If `self` contains no `'/'`, returns `false`; else returns `true`.
+    ///
+    /// # Example
+    ///
+    /// ```rust,ignore
+    /// let mut path = VirtualPath("/foo/bar".to_string());
+    /// path.pop();
+    /// assert_eq!(path.0, "/foo");
+    /// path.pop();
+    /// assert_eq!(path.0, "");
+    /// ```
     fn pop(&mut self) -> bool {
         let pos = match self.0.rfind('/') {
             Some(pos) => pos,
@@ -310,6 +339,17 @@ impl VirtualPath {
         self.0 = self.0[..pos].to_string();
         true
     }
+
+    /// Append the given *relative* path `path` to `self`.
+    ///
+    /// This will resolve any leading `"../"` in `path` before appending it.
+    ///
+    /// Returns [`None`] if `path` has more leading `"../"` than the number of
+    /// components in `self`.
+    ///
+    /// # Notes
+    ///
+    /// In practice, appending here means `self/path` as strings.
     fn join(&self, mut path: &str) -> Option<VirtualPath> {
         let mut res = self.clone();
         while path.starts_with("../") {
@@ -322,7 +362,18 @@ impl VirtualPath {
         Some(res)
     }
 
-    pub(crate) fn name_and_extension(&self) -> Option<(&str, Option<&str>)> {
+    /// Returns `self`'s base name and file extension.
+    ///
+    /// # Returns
+    /// - `None` if `self` ends with `"//"`.
+    /// - `Some((name, None))` if `self`'s base contains no `.`, or only one `.` at
+    /// the start.
+    /// - `Some((name, Some(extension))` else.
+    ///
+    /// # Note
+    /// The extension will not contains `.`. This means `"/foo/bar.baz.rs"` will
+    /// return `Some(("bar.baz", Some("rs"))`.
+    fn name_and_extension(&self) -> Option<(&str, Option<&str>)> {
         let file_path = if self.0.ends_with('/') { &self.0[..&self.0.len() - 1] } else { &self.0 };
         let file_name = match file_path.rfind('/') {
             Some(position) => &file_path[position + 1..],