vfs: Flesh out MemoryBackend

vfs/src/lib.rs

@@ -65,7 +65,7 @@ pub trait VfsBackend: sealed::Sealed + Send + 'static {
 ///
 /// [std::fs::DirEntry]: https://doc.rust-lang.org/stable/std/fs/struct.DirEntry.html
 pub struct DirEntry {
-    path: PathBuf,
+    pub(crate) path: PathBuf,
 }
 
 impl DirEntry {
@@ -78,7 +78,7 @@ impl DirEntry {
 ///
 /// [std::fs::ReadDir]: https://doc.rust-lang.org/stable/std/fs/struct.ReadDir.html
 pub struct ReadDir {
-    inner: Box<dyn Iterator<Item = io::Result<DirEntry>>>,
+    pub(crate) inner: Box<dyn Iterator<Item = io::Result<DirEntry>>>,
 }
 
 impl Iterator for ReadDir {
@@ -94,7 +94,7 @@ impl Iterator for ReadDir {
 /// [std::fs::Metadata]: https://doc.rust-lang.org/stable/std/fs/struct.Metadata.html
 #[derive(Debug)]
 pub struct Metadata {
-    is_file: bool,
+    pub(crate) is_file: bool,
 }
 
 impl Metadata {

vfs/src/memory_backend.rs

@@ -1,8 +1,8 @@
-use std::collections::{BTreeSet, HashMap};
+use std::collections::{BTreeSet, HashMap, VecDeque};
 use std::io;
 use std::path::{Path, PathBuf};
 
-use crate::{Metadata, ReadDir, VfsBackend, VfsEvent, VfsSnapshot};
+use crate::{DirEntry, Metadata, ReadDir, VfsBackend, VfsEvent, VfsSnapshot};
 
 /// `VfsBackend` that reads from an in-memory filesystem, intended for setting
 /// up testing scenarios quickly.
@@ -20,7 +20,11 @@ impl MemoryBackend {
         }
     }
 
-    pub fn load_snapshot<P: Into<PathBuf>>(&mut self, path: P, snapshot: VfsSnapshot) {
+    pub fn load_snapshot<P: Into<PathBuf>>(
+        &mut self,
+        path: P,
+        snapshot: VfsSnapshot,
+    ) -> io::Result<()> {
         let path = path.into();
 
         if let Some(parent_path) = path.parent() {
@@ -28,10 +32,7 @@ impl MemoryBackend {
                 if let Entry::Dir { children } = parent_entry {
                     children.insert(path.clone());
                 } else {
-                    panic!(
-                        "Tried to load snapshot as child of file, {}",
-                        parent_path.display()
-                    );
+                    return must_be_dir(parent_path);
                 }
             } else {
                 self.orphans.insert(path.clone());
@@ -54,10 +55,25 @@ impl MemoryBackend {
 
                 for (child_name, child) in children {
                     let full_path = path.join(child_name);
-                    self.load_snapshot(full_path, child);
+                    self.load_snapshot(full_path, child)?;
                 }
             }
-        };
+        }
+
+        Ok(())
+    }
+
+    fn remove(&mut self, root_path: PathBuf) {
+        self.orphans.remove(&root_path);
+
+        let mut to_remove = VecDeque::new();
+        to_remove.push_back(root_path);
+
+        while let Some(path) = to_remove.pop_front() {
+            if let Some(Entry::Dir { children }) = self.entries.remove(&path) {
+                to_remove.extend(children);
+            }
+        }
     }
 }
 
@@ -69,46 +85,68 @@ enum Entry {
 }
 
 impl VfsBackend for MemoryBackend {
-    fn read(&mut self, _path: &Path) -> io::Result<Vec<u8>> {
-        Err(io::Error::new(
-            io::ErrorKind::Other,
-            "MemoryBackend doesn't do anything",
-        ))
+    fn read(&mut self, path: &Path) -> io::Result<Vec<u8>> {
+        match self.entries.get(path) {
+            Some(Entry::File { contents }) => Ok(contents.clone()),
+            Some(Entry::Dir { .. }) => must_be_file(path),
+            None => not_found(path),
+        }
     }
 
-    fn write(&mut self, _path: &Path, _data: &[u8]) -> io::Result<()> {
-        Err(io::Error::new(
-            io::ErrorKind::Other,
-            "MemoryBackend doesn't do anything",
-        ))
+    fn write(&mut self, path: &Path, data: &[u8]) -> io::Result<()> {
+        self.load_snapshot(
+            path,
+            VfsSnapshot::File {
+                contents: data.to_owned(),
+            },
+        )
     }
 
-    fn read_dir(&mut self, _path: &Path) -> io::Result<ReadDir> {
-        Err(io::Error::new(
-            io::ErrorKind::Other,
-            "MemoryBackend doesn't do anything",
-        ))
+    fn read_dir(&mut self, path: &Path) -> io::Result<ReadDir> {
+        match self.entries.get(path) {
+            Some(Entry::Dir { children }) => {
+                let iter = children
+                    .clone()
+                    .into_iter()
+                    .map(|path| Ok(DirEntry { path }));
+
+                Ok(ReadDir {
+                    inner: Box::new(iter),
+                })
+            }
+            Some(Entry::File { .. }) => must_be_dir(path),
+            None => not_found(path),
+        }
     }
 
-    fn remove_file(&mut self, _path: &Path) -> io::Result<()> {
-        Err(io::Error::new(
-            io::ErrorKind::Other,
-            "MemoryBackend doesn't do anything",
-        ))
+    fn remove_file(&mut self, path: &Path) -> io::Result<()> {
+        match self.entries.get(path) {
+            Some(Entry::File { .. }) => {
+                self.remove(path.to_owned());
+                Ok(())
+            }
+            Some(Entry::Dir { .. }) => must_be_file(path),
+            None => not_found(path),
+        }
     }
 
-    fn remove_dir_all(&mut self, _path: &Path) -> io::Result<()> {
-        Err(io::Error::new(
-            io::ErrorKind::Other,
-            "MemoryBackend doesn't do anything",
-        ))
+    fn remove_dir_all(&mut self, path: &Path) -> io::Result<()> {
+        match self.entries.get(path) {
+            Some(Entry::Dir { .. }) => {
+                self.remove(path.to_owned());
+                Ok(())
+            }
+            Some(Entry::File { .. }) => must_be_dir(path),
+            None => not_found(path),
+        }
     }
 
-    fn metadata(&mut self, _path: &Path) -> io::Result<Metadata> {
-        Err(io::Error::new(
-            io::ErrorKind::Other,
-            "MemoryBackend doesn't do anything",
-        ))
+    fn metadata(&mut self, path: &Path) -> io::Result<Metadata> {
+        match self.entries.get(path) {
+            Some(Entry::File { .. }) => Ok(Metadata { is_file: true }),
+            Some(Entry::Dir { .. }) => Ok(Metadata { is_file: false }),
+            None => not_found(path),
+        }
     }
 
     fn event_receiver(&self) -> crossbeam_channel::Receiver<VfsEvent> {
@@ -116,16 +154,37 @@ impl VfsBackend for MemoryBackend {
     }
 
     fn watch(&mut self, _path: &Path) -> io::Result<()> {
-        Err(io::Error::new(
-            io::ErrorKind::Other,
-            "MemoryBackend doesn't do anything",
-        ))
+        Ok(())
     }
 
     fn unwatch(&mut self, _path: &Path) -> io::Result<()> {
-        Err(io::Error::new(
-            io::ErrorKind::Other,
-            "MemoryBackend doesn't do anything",
-        ))
+        Ok(())
     }
 }
+
+fn must_be_file<T>(path: &Path) -> io::Result<T> {
+    Err(io::Error::new(
+        io::ErrorKind::Other,
+        format!(
+            "path {} was a directory, but must be a file",
+            path.display()
+        ),
+    ))
+}
+
+fn must_be_dir<T>(path: &Path) -> io::Result<T> {
+    Err(io::Error::new(
+        io::ErrorKind::Other,
+        format!(
+            "path {} was a file, but must be a directory",
+            path.display()
+        ),
+    ))
+}
+
+fn not_found<T>(path: &Path) -> io::Result<T> {
+    Err(io::Error::new(
+        io::ErrorKind::NotFound,
+        format!("path {} not found", path.display()),
+    ))
+}