Add `Dir` equivalents of `fs::metadata` & `fs::symlink_metadata` by RalfJung · Pull Request #163024 · rust-lang/rust

RalfJung · 2026-09-19T15:29:18Z

This adds methods to Dir that allow querying the metadata of files/directories relative to a Dir. Miri would really like to be able to do this so I figured I'd give it a shot. :)

The first commit refactors the Unix DirEntry methods a bit with cfg_select to avoid repeating the cfg condition.

Tracking issue: #120426

try-jobs: test-x86_64-msvc-1

rustbot · 2026-09-19T15:29:22Z

Any special-casing of Miri in the standard library requires review.

cc @rust-lang/miri

rustbot · 2026-09-19T15:29:24Z

r? @Mark-Simulacrum

rustbot has assigned @Mark-Simulacrum.
They will have a look at your PR within the next two weeks and either review your PR or reassign to another reviewer.

Use r? to explicitly pick a reviewer

Why was this reviewer chosen?

The reviewer was selected based on:

Owners of files modified in this PR: @ChrisDenton, libs
@ChrisDenton, libs expanded to 13 candidates
Random selection from 6 candidates

RalfJung · 2026-09-19T15:32:42Z

+    fn metadata_at_native(&self, path: &[u16], reparse: ReparsePoint) -> io::Result<FileAttr> {
+        let mut opts = OpenOptions::new();
+        // No read or write permissions are necessary
+        opts.access_mode(0);
+        opts.custom_flags(c::FILE_FLAG_BACKUP_SEMANTICS | reparse.as_flag());
+
+        // Attempt to open the file normally.
+        // FIXME: `fs::metadata` has a fallback path when that fails. That has not (yet) been ported
+        // to directory handles.
+        let name = UnicodeStrRef::from_slice(path);
+        let object_attributes = c::OBJECT_ATTRIBUTES {
+            RootDirectory: self.handle.as_raw_handle(),
+            ObjectName: name.as_ptr().cast_mut(),
+            ..c::OBJECT_ATTRIBUTES::with_length()
+        };
+        let create_opt = 0; // We don't want to create anything, only open existing things.
+        let handle = unsafe { nt_create_file(&opts, &object_attributes, create_opt)? };
+        File { handle }.file_attr()
+    }


@ChrisDenton I hope this makes sense, I am mostly guessing here.^^ Especially about passing 0 for create_opt; the only other caller passes if dir { c::FILE_DIRECTORY_FILE } else { c::FILE_NON_DIRECTORY_FILE } but we cannot know in advance whether this is a directory or a file...

I also didn't copy the complicated fallback stuff from fs::metadata as I had no idea what that would look like with directory handles. I hope this first step is still useful and we can always add more fallback code later?

View changes since the review

I left some notes but essentially NT APIs are a bit different to the higher level win32 APIs. I'm ok with a partial implementation since I think I'm likely going to be rewriting (or at least refactoring) a lot of this anyway.

Add `Dir::metadata_at` & `Dir::symlink_metadata_at` try-job: test*msvc*

RalfJung · 2026-09-19T17:44:34Z

Hm...

thread 'fs::tests::test_dir_metadata_at' (6552) panicked at library\std\src\fs\tests.rs:2812:5:
dir.open_file_with("subdir/bar.txt",
&OpenOptions::new().create(true).write(true)) failed with: The filename, directory name, or volume label syntax is incorrect. (os error 123)

Does this not support /? That would then likely affect the other Dir methods as well and would be inconsistent with the normal fs methods AFAIK.

This isn't even in my new method, the failure is from

dir.open_file_with("subdir/bar.txt", &OpenOptions::new().create(true).write(true))

I should file an issue... EDIT: #163032

Add `Dir::metadata_at` & `Dir::symlink_metadata_at` try-job: test-*-msvc-1

RalfJung · 2026-09-19T18:00:48Z

+    /// }
+    /// ```
+    #[unstable(feature = "dirfd", issue = "120426")]
+    pub fn metadata_at<P: AsRef<Path>>(&self, path: P) -> io::Result<Metadata> {


The name does match the operation in fs that it corresponds to -- but Dir::metadata is already taken. So I went for a new name, inspired by the Linux naming scheme with the *at calls working on directory handles.

Alternatives that have been suggested or that I can think of:

Use just metadata for this, and ask people to write dir.metadata(".") to get the metadata of the directory itself. But that seems silly in terms of the extra syscalls it causes.

Use just metadata for this, and use self_metadata/metadata_self or so for the metadata of the directory handle itself.

View changes since the review

I'll be honest, I don't love the name and it would be especially weird if this would be our only use of the _at suffix (imho).

Another alternative I can think of is just making people open the fd and call fstat but I think that would be more controversial.

Fair. I got rid of the _at suffix and renamed the old method to self_metadata.

Add `Dir::metadata_at` & `Dir::symlink_metadata_at` try-job: test-*-msvc-1

RalfJung · 2026-09-29T10:02:08Z

@bors try jobs=various,android

rust-bors · 2026-09-29T10:02:11Z

❌ Encountered an error while executing command

RalfJung · 2026-09-29T10:02:24Z

@bors try jobs=various,android

rust-bors · 2026-09-29T10:02:27Z

❌ Encountered an error while executing command

RalfJung · 2026-09-29T10:23:07Z

@bors try jobs=various,android

rust-bors · 2026-09-29T10:23:09Z

❌ Encountered an error while executing command

RalfJung · 2026-09-29T10:23:19Z

@bors try cancel

rust-bors · 2026-09-29T10:23:21Z

❌ Encountered an error while executing command

Kobzol · 2026-09-29T10:30:52Z

@bors r-

rust-bors · 2026-09-29T10:30:55Z

❌ Encountered an error while executing command

Kobzol · 2026-09-29T10:50:17Z

@bors try jobs=various,android

Add `Dir` equivalents of `fs::metadata` & `fs::symlink_metadata` try-job: *various* try-job: *android*

rust-bors · 2026-09-29T12:47:24Z

☀️ Try build successful (CI)
Build commit: a624b40 (a624b4007ca55a0d20290262ae550d452880c639)
Base parent: 80a4f6c (80a4f6cdbdc30afa1f27c830386361d22b161286)

RalfJung · 2026-09-29T12:48:13Z

@bors r=ChrisDenton

rust-bors · 2026-09-29T12:48:16Z

📌 Commit 5b172d9 has been approved by ChrisDenton

It is now in the queue for this repository.

…enton Add `Dir` equivalents of `fs::metadata` & `fs::symlink_metadata` This adds methods to `Dir` that allow querying the metadata of files/directories relative to a `Dir`. Miri would [really like](rust-lang/miri#5327) to be able to do this so I figured I'd give it a shot. :) The first commit refactors the Unix `DirEntry` methods a bit with `cfg_select` to avoid repeating the `cfg` condition. Tracking issue: rust-lang#120426 try-jobs: test-x86_64-msvc-1

…uwer Rollup of 3 pull requests Successful merges: - #163024 (Add `Dir` equivalents of `fs::metadata` & `fs::symlink_metadata`) - #163279 (const and NonZero impl for clamp_magnitude()) - #163361 (Specialize `advance_back_by` like the forward version)

…uwer Rollup of 4 pull requests Successful merges: - #163024 (Add `Dir` equivalents of `fs::metadata` & `fs::symlink_metadata`) - #162839 (Bump min Emscripten version to 4.0, drop deprecated -sWASM_BIGINT for wasm32-unknown-emscripten) - #163370 (Fix incorrect typo suggestion for `struct field` shorthands) - #163471 (do not suggest capturing `'_` twice in `use<...>` for E0700)

Rollup merge of #163024 - RalfJung:dir-metadata-at, r=ChrisDenton Add `Dir` equivalents of `fs::metadata` & `fs::symlink_metadata` This adds methods to `Dir` that allow querying the metadata of files/directories relative to a `Dir`. Miri would [really like](rust-lang/miri#5327) to be able to do this so I figured I'd give it a shot. :) The first commit refactors the Unix `DirEntry` methods a bit with `cfg_select` to avoid repeating the `cfg` condition. Tracking issue: #120426 try-jobs: test-x86_64-msvc-1

…uwer Rollup of 4 pull requests Successful merges: - rust-lang/rust#163024 (Add `Dir` equivalents of `fs::metadata` & `fs::symlink_metadata`) - rust-lang/rust#162839 (Bump min Emscripten version to 4.0, drop deprecated -sWASM_BIGINT for wasm32-unknown-emscripten) - rust-lang/rust#163370 (Fix incorrect typo suggestion for `struct field` shorthands) - rust-lang/rust#163471 (do not suggest capturing `'_` twice in `use<...>` for E0700)

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-libs Relevant to the library team, which will review and decide on the PR/issue. labels Sep 19, 2026

rustbot assigned Mark-Simulacrum Sep 19, 2026

RalfJung mentioned this pull request Sep 19, 2026

Tracking Issue for directory handles #120426

Open

4 of 13 tasks

RalfJung commented Sep 19, 2026

View reviewed changes

This comment was marked as resolved.

Sign in to view