ignore: fix performance regression on Windows

This commit fixes a performance regression in Windows that resulted from
fallout from fixing #705. In particular, we introduced an additional
stat call for every single directory entry, which can be quite
disastrous for performance.

There is a corresponding companion PR that fixes the same bug in
walkdir: https://github.com/BurntSushi/walkdir/pull/96

Fixes #820

Cargo.lock

@@ -125,7 +125,7 @@ dependencies = [
  "same-file 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "tempdir 0.3.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "thread_local 0.3.5 (registry+https://github.com/rust-lang/crates.io-index)",
- "walkdir 2.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "walkdir 2.1.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "winapi 0.3.4 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -331,7 +331,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
 name = "walkdir"
-version = "2.1.3"
+version = "2.1.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "same-file 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -401,7 +401,7 @@ dependencies = [
 "checksum unreachable 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)" = "382810877fe448991dfc7f0dd6e3ae5d58088fd0ea5e35189655f84e6814fa56"
 "checksum utf8-ranges 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)" = "662fab6525a98beff2921d7f61a39e7d59e0b425ebc7d0d9e66d316e55124122"
 "checksum void 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)" = "6a02e4885ed3bc0f2de90ea6dd45ebcbb66dacffe03547fadbb0eeae2770887d"
-"checksum walkdir 2.1.3 (registry+https://github.com/rust-lang/crates.io-index)" = "b167e9a4420d8dddb260e70c90a4a375a1e5691f21f70e715553da87b6c2503a"
+"checksum walkdir 2.1.4 (registry+https://github.com/rust-lang/crates.io-index)" = "63636bd0eb3d00ccb8b9036381b526efac53caf112b7783b730ab3f8e44da369"
 "checksum winapi 0.3.4 (registry+https://github.com/rust-lang/crates.io-index)" = "04e3bd221fcbe8a271359c04f21a76db7d0c6028862d1bb5512d85e1e2eb5bb3"
 "checksum winapi-i686-pc-windows-gnu 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)" = "ac3b87c63620426dd9b991e5ce0329eff545bccbbb34f3be09ff6fb6ab51b7b6"
 "checksum winapi-x86_64-pc-windows-gnu 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)" = "712e227841d057c1ee1cd2fb22fa7e5a5461ae8e48fa2ca79ec42cfc1931183f"

ignore/src/walk.rs

@@ -249,6 +249,14 @@ struct DirEntryRaw {
     /// The underlying inode number (Unix only).
     #[cfg(unix)]
     ino: u64,
+    /// The underlying metadata (Windows only). We store this on Windows
+    /// because this comes for free while reading a directory.
+    ///
+    /// We use this to determine whether an entry is a directory or not, which
+    /// works around a bug in Rust's standard library:
+    /// https://github.com/rust-lang/rust/issues/46484
+    #[cfg(windows)]
+    metadata: fs::Metadata,
 }
 
 impl fmt::Debug for DirEntryRaw {
@@ -274,6 +282,20 @@ impl DirEntryRaw {
     }
 
     fn metadata(&self) -> Result<Metadata, Error> {
+        self.metadata_internal()
+    }
+
+    #[cfg(windows)]
+    fn metadata_internal(&self) -> Result<fs::Metadata, Error> {
+        if self.follow_link {
+            fs::metadata(&self.path)
+        } else {
+            Ok(self.metadata.clone())
+        }.map_err(|err| Error::Io(io::Error::from(err)).with_path(&self.path))
+    }
+
+    #[cfg(not(windows))]
+    fn metadata_internal(&self) -> Result<fs::Metadata, Error> {
         if self.follow_link {
             fs::metadata(&self.path)
         } else {
@@ -309,21 +331,29 @@ impl DirEntryRaw {
                 err: Box::new(err),
             }
         })?;
-        Ok(DirEntryRaw::from_entry_os(depth, ent, ty))
+        DirEntryRaw::from_entry_os(depth, ent, ty)
     }
 
-    #[cfg(not(unix))]
+    #[cfg(windows)]
     fn from_entry_os(
         depth: usize,
         ent: &fs::DirEntry,
         ty: fs::FileType,
-    ) -> DirEntryRaw {
+    ) -> Result<DirEntryRaw, Error> {
-        DirEntryRaw {
+        let md = ent.metadata().map_err(|err| {
+            let err = Error::Io(io::Error::from(err)).with_path(ent.path());
+            Error::WithDepth {
+                depth: depth,
+                err: Box::new(err),
+            }
+        })?;
+        Ok(DirEntryRaw {
             path: ent.path(),
             ty: ty,
             follow_link: false,
             depth: depth,
-        }
+            metadata: md,
+        })
     }
 
     #[cfg(unix)]
@@ -331,16 +361,16 @@ impl DirEntryRaw {
         depth: usize,
         ent: &fs::DirEntry,
         ty: fs::FileType,
-    ) -> DirEntryRaw {
+    ) -> Result<DirEntryRaw, Error> {
         use std::os::unix::fs::DirEntryExt;
 
-        DirEntryRaw {
+        Ok(DirEntryRaw {
             path: ent.path(),
             ty: ty,
             follow_link: false,
             depth: depth,
             ino: ent.ino(),
-        }
+        })
     }
 
     #[cfg(not(unix))]
@@ -353,6 +383,7 @@ impl DirEntryRaw {
             ty: md.file_type(),
             follow_link: true,
             depth: depth,
+            metadata: md,
         })
     }