manifest: add count_files() to Manifest trait

Summary:
add count_files() to Manifest trait, this is a bit faster than calling files()
function, then count the files.

Reviewed By: muirdm

Differential Revision: D69528661

fbshipit-source-id: 7eefe9299841740afad1c00c4e502d8aace62591

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

@@ -336,6 +336,19 @@ impl Manifest for TreeManifest {
         Box::new(files)
     }
 
+    #[tracing::instrument(skip_all)]
+    fn count_files<'a, M: 'static + Matcher + Sync + Send>(&'a self, matcher: M) -> Result<u64> {
+        // PERF: the `bfs_iter()` can be optimized to avoid file path construction.
+        bfs_iter(self.store.clone(), &[&self.root], matcher).try_fold(0, |acc, result| {
+            let (_, metadata) = result?;
+            if let FsNodeMetadata::File(_) = metadata {
+                Ok(acc + 1)
+            } else {
+                Ok(acc)
+            }
+        })
+    }
+
     /// Returns an iterator over all the directories that are present in the
     /// tree.
     ///

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

@@ -89,6 +89,14 @@ pub trait Manifest {
         matcher: M,
     ) -> Box<dyn Iterator<Item = Result<File>> + 'a>;
 
+    /// Returns the number of files in the Manifest that satisfy the given Matcher.
+    fn count_files<'a, M: 'static + Matcher + Sync + Send>(&'a self, matcher: M) -> Result<u64> {
+        self.files(matcher).try_fold(0, |acc, result| {
+            let _ = result?;
+            Ok(acc + 1)
+        })
+    }
+
     /// Returns an iterator over all directories found in the paths of the files in the Manifest
     /// that satisfy the given Matcher.
     // TODO: add default implementation

eden/scm/sapling/utils/subtreeutil.py

@@ -366,7 +366,7 @@ def validate_file_count(repo, ctx, paths):
     mf = ctx.manifest()
     for p in paths:
         matcher = matchmod.match(repo.root, "", [f"path:{p}"])
-        count = mf.count(matcher)
+        count = mf.countfiles(matcher)
         if count > max_file_count:
             raise error.Abort(
                 _("subtree path '%s' includes too many files: %d (max: %d)")

eden/scm/saplingnative/bindings/modules/pymanifest/src/lib.rs

@@ -158,14 +158,14 @@ py_class!(pub class treemanifest |py| {
     }
 
     /// Count the number of files that match the predicate passed to the function.
-    def count(&self, pymatcher: PyObject) -> PyResult<u64> {
-        // PERF: the `tree.files()` can be optimized to avoid file path construction.
+    def countfiles(&self, pymatcher: PyObject) -> PyResult<u64> {
         let tree = self.underlying(py);
         let matcher = extract_matcher(py, pymatcher)?.0;
-        let count = py.allow_threads(move || -> u64 {
+        let result = py.allow_threads(move || -> Result<u64> {
             let tree = tree.read();
-            tree.files(matcher).fold(0, |acc, _f| acc + 1)
+            tree.count_files(matcher)
         });
+        let count = result.map_pyerr(py)?;
         Ok(count)
     }