manifest-tree: implement TryFrom for directly converting from a serialized manifest tree entry to a manifest::List

Summary: Allow `manifest-tree::Entry` to be constructed directly by other crates, and introduce a `TryFrom` conversion to `manifest::List::Directory`. This will be used by the scmstore `BackingStore` implementation to avoid having to rely on the `TreeStore` trait, which does not support batching.

Reviewed By: kulshrax

Differential Revision: D30282738

fbshipit-source-id: 590350dd53217fa8a181e91b194abca753a8adbe

eden/scm/lib/manifest-tree/src/lib.rs

@@ -29,7 +29,10 @@ use pathmatcher::Matcher;
 use types::{HgId, Key, PathComponent, PathComponentBuf, RepoPath, RepoPathBuf};
 
 pub(crate) use self::link::Link;
-pub use self::{diff::Diff, store::TreeStore};
+pub use self::{
+    diff::Diff,
+    store::{Entry as TreeEntry, TreeStore},
+};
 use crate::{
     iter::{BfsIter, DfsCursor, Step},
     link::{DirLink, Durable, DurableEntry, Ephemeral, Leaf},

eden/scm/lib/manifest-tree/src/store.rs

@@ -6,6 +6,7 @@
  */
 
 use std::{
+    convert::TryFrom,
     str::{from_utf8, FromStr},
     sync::Arc,
 };
@@ -13,7 +14,7 @@ use std::{
 use anyhow::{format_err, Result};
 use bytes::{Bytes, BytesMut};
 
-use manifest::FileType;
+use manifest::{FileMetadata, FileType, FsNodeMetadata};
 use types::{HgId, Key, PathComponent, PathComponentBuf, RepoPath};
 
 /// The `TreeStore` is an abstraction layer for the tree manifest that decouples how or where the
@@ -100,7 +101,7 @@ impl InnerStore {
 /// representation. For this serialization format it is important that they don't contain
 /// `\0` or `\n`.
 #[derive(Clone, Debug, Eq, Hash, Ord, PartialEq, PartialOrd)]
-pub struct Entry(Bytes);
+pub struct Entry(pub Bytes);
 
 pub struct EntryMut(BytesMut);
 
@@ -200,6 +201,27 @@ impl<'a> Iterator for Elements<'a> {
     }
 }
 
+impl TryFrom<Entry> for manifest::List {
+    type Error = anyhow::Error;
+
+    fn try_from(v: Entry) -> Result<Self> {
+        let mut entries = Vec::new();
+        for entry in v.elements() {
+            let entry = entry?;
+            entries.push((
+                entry.component,
+                match entry.flag {
+                    Flag::Directory => FsNodeMetadata::Directory(Some(entry.hgid)),
+                    Flag::File(file_type) => {
+                        FsNodeMetadata::File(FileMetadata::new(entry.hgid, file_type))
+                    }
+                },
+            ))
+        }
+        Ok(manifest::List::Directory(entries))
+    }
+}
+
 impl Element {
     pub fn new(component: PathComponentBuf, hgid: HgId, flag: Flag) -> Element {
         Element {