Add std::fs::{Home|Media}Dirs

library/std/src/env.rs

@@ -606,7 +606,6 @@ impl Error for JoinPathsError {
 /// For example, [XDG Base Directories] on Unix or the `LOCALAPPDATA` and `APPDATA` environment variables on Windows.
 ///
 /// [XDG Base Directories]: https://specifications.freedesktop.org/basedir-spec/latest/
-//  feature(xdg_basedir): This should link to std::os::unix::xdg once it's stabilized
 ///
 /// # Unix
 ///

library/std/src/fs.rs

@@ -48,6 +48,13 @@ use crate::sys::{AsInner, AsInnerMut, FromInner, IntoInner, fs as fs_imp};
 use crate::time::SystemTime;
 use crate::{error, fmt};
 
+pub(crate) mod dirs;
+
+#[unstable(feature = "dir_discovery", issue = "157515")]
+pub use self::dirs::HomeDirs;
+#[unstable(feature = "media_dir_discovery", issue = "157515")]
+pub use self::dirs::MediaDirs;
+
 /// An object providing access to an open file on the filesystem.
 ///
 /// An instance of a `File` can be read and/or written depending on what options

library/std/src/os/darwin/fs.rs

@@ -7,6 +7,13 @@ use crate::fs::{self, Metadata};
 use crate::sys::{AsInner, AsInnerMut, IntoInner};
 use crate::time::SystemTime;
 
+mod dirs;
+
+#[unstable(feature = "dir_discovery", issue = "157515")]
+pub use self::dirs::HomeDirsExt;
+#[unstable(feature = "media_dir_discovery", issue = "157515")]
+pub use self::dirs::MediaDirsExt;
+
 /// OS-specific extensions to [`fs::Metadata`].
 ///
 /// [`fs::Metadata`]: crate::fs::Metadata

library/std/src/os/darwin/fs/dirs.rs

@@ -0,0 +1,320 @@
+use crate::env;
+use crate::fs::{HomeDirs, MediaDirs};
+use crate::io::{self, ErrorKind, const_error};
+use crate::path::PathBuf;
+
+trait Sealed {}
+impl Sealed for HomeDirs {}
+impl Sealed for MediaDirs {}
+
+/// Darwin-specific extensions to [`fs::HomeDirs`](HomeDirs).
+#[unstable(feature = "dir_discovery", issue = "157515")]
+#[expect(private_bounds, reason = "sealed")]
+pub trait HomeDirsExt: Sized + Sealed {
+    /// Load the standard user directory paths for the current user.
+    ///
+    /// On iOS, tvOS, watchOS, visionOS, and sandboxed macOS applications,
+    /// these directories are within the application's sandbox bundle. Outside
+    /// the sandbox, these are subdirectories of the `~/Library` directory on
+    /// macOS.
+    ///
+    /// The produced directory paths are not guaranteed to be the canonical
+    /// paths to the directories; they are allowed to be sandbox-redirected
+    /// paths as long as the directory is accessible there.
+    ///
+    /// The loaded common directories are:
+    ///
+    /// | `HomeDirs` | [`NSSearchPathDirectory`] |
+    /// | ---------- | ----------------------- |
+    /// | [`cache_home`] | [`NSCachesDirectory`] (`~/Library/Caches`) |
+    /// | [`config_home`] | [`NSApplicationSupportDirectory`] (`~/Library/Application Support`) |
+    /// | [`data_home`] | [`NSApplicationSupportDirectory`] (`~/Library/Application Support`) |
+    /// | [`state_home`] | [`NSApplicationSupportDirectory`] (`~/Library/Application Support`) |
+    ///
+    /// Note that the Application Support directory is used for the config,
+    /// data, and state directories. It is always possible for multiple user
+    /// directories to be configured to the same path, but this is the common
+    /// configuration on Apple platforms, making it even more important to not
+    /// assume files in different user directories cannot alias each other.
+    ///
+    /// # Errors
+    ///
+    /// Errors if the the [user home](env::home_dir) cannot be determined.
+    //  Errors due to the underlying sysdir(3) API should never occur, as
+    //  - the user domain only has one directory for each search path;
+    //  - the user domain always returns subdirectory paths of `~`;
+    //  - the username plus OS defined path segments cannot exceed PATH_MAX; and
+    //  - the username and OS defined path segments are always valid UTF-8.
+    ///
+    /// # Implementation-specific behavior
+    ///
+    /// Uses the `sysdir(3)` API from `libSystem` to discover the standard
+    /// user directories.
+    ///
+    /// This behavior may change in the future. One example change that we
+    /// explicitly reserve the right to make is to load additional common
+    /// directories not currently in this list.
+    ///
+    /// [`cache_home`]: HomeDirs::cache_home
+    /// [`config_home`]: HomeDirs::config_home
+    /// [`data_home`]: HomeDirs::data_home
+    /// [`state_home`]: HomeDirs::state_home
+    ///
+    /// [`NSSearchPathDirectory`]: https://developer.apple.com/documentation/foundation/filemanager/searchpathdirectory?language=objc
+    /// [`NSCachesDirectory`]: https://developer.apple.com/documentation/foundation/filemanager/searchpathdirectory/cachesdirectory?language=objc
+    /// [`NSApplicationSupportDirectory`]: https://developer.apple.com/documentation/foundation/filemanager/searchpathdirectory/applicationsupportdirectory?language=objc
+    #[unstable(feature = "dir_discovery", issue = "157515")]
+    fn sysdir() -> io::Result<Self>;
+}
+
+/// Darwin-specific extensions to [`fs::MediaDirs`](MediaDirs).
+#[unstable(feature = "media_dir_discovery", issue = "157515")]
+#[expect(private_bounds, reason = "sealed")]
+pub trait MediaDirsExt: Sized + Sealed {
+    /// Load the standard user directory paths for the current user.
+    ///
+    /// The produced directory paths are not guaranteed to be the canonical
+    /// paths to the directories; they are allowed to be sandbox-redirected
+    /// paths as long as the directory is accessible there.
+    ///
+    /// The loaded common directories are:
+    ///
+    /// | `MediaDirs` | [`NSSearchPathDirectory`] |
+    /// | ---------- | ----------------------- |
+    /// | [`desktop`] | [`NSDesktopDirectory`] (`~/Desktop`) |
+    /// | [`documents`] | [`NSDocumentDirectory`] (`~/Documents`) |
+    /// | [`downloads`] | [`NSDownloadsDirectory`] |
+    /// | [`music`] | [`NSMusicDirectory`] (`~/Music`) |
+    /// | [`pictures`] | [`NSPicturesDirectory`] (`~/Pictures`) |
+    /// | [`videos`] | [`NSMoviesDirectory`] (`~/Movies`) |
+    ///
+    /// # Errors
+    ///
+    /// Errors if the the [user home](env::home_dir) cannot be determined.
+    //  Errors due to the underlying sysdir(3) API should never occur, as
+    //  - the user domain only has one directory for each search path;
+    //  - the user domain always returns subdirectory paths of `~`;
+    //  - the username plus OS defined path segments cannot exceed PATH_MAX; and
+    //  - the username and OS defined path segments are always valid UTF-8.
+    ///
+    /// # Implementation-specific behavior
+    ///
+    /// Uses the `sysdir(3)` API from `libSystem` to discover the standard
+    /// user directories.
+    ///
+    /// This behavior may change in the future. One example change that we
+    /// explicitly reserve the right to make is to load additional common
+    /// directories not currently in this list.
+    ///
+    /// [`desktop`]: MediaDirs::desktop
+    /// [`documents`]: MediaDirs::documents
+    /// [`downloads`]: MediaDirs::downloads
+    /// [`music`]: MediaDirs::music
+    /// [`pictures`]: MediaDirs::pictures
+    /// [`videos`]: MediaDirs::videos
+    ///
+    /// [`NSSearchPathDirectory`]: https://developer.apple.com/documentation/foundation/filemanager/searchpathdirectory?language=objc
+    /// [`NSDesktopDirectory`]: https://developer.apple.com/documentation/foundation/filemanager/searchpathdirectory/desktopdirectory?language=objc
+    /// [`NSDocumentDirectory`]: https://developer.apple.com/documentation/foundation/filemanager/searchpathdirectory/documentdirectory?language=objc
+    /// [`NSDownloadsDirectory`]: https://developer.apple.com/documentation/foundation/filemanager/searchpathdirectory/downloadsdirectory?language=objc
+    /// [`NSMusicDirectory`]: https://developer.apple.com/documentation/foundation/filemanager/searchpathdirectory/musicdirectory?language=objc
+    /// [`NSPicturesDirectory`]: https://developer.apple.com/documentation/foundation/filemanager/searchpathdirectory/picturesdirectory?language=objc
+    /// [`NSSharedPublicDirectory`]: https://developer.apple.com/documentation/foundation/filemanager/searchpathdirectory/sharedpublicdirectory?language=objc
+    /// [`NSMoviesDirectory`]: https://developer.apple.com/documentation/foundation/filemanager/searchpathdirectory/moviesdirectory?language=objc
+    #[unstable(feature = "media_dir_discovery", issue = "157515")]
+    fn sysdir() -> io::Result<Self>;
+}
+
+fn user_home() -> io::Result<PathBuf> {
+    env::home_dir()
+        .filter(|p| !p.is_empty())
+        .ok_or(const_error!(ErrorKind::NotFound, "no home directory"))
+}
+
+#[unstable(feature = "dir_discovery", issue = "157515")]
+#[cfg(target_vendor = "apple")]
+impl HomeDirsExt for HomeDirs {
+    fn sysdir() -> io::Result<Self> {
+        use libc::sysdir_search_path_directory_t::*;
+
+        let mut dirs = HomeDirs::empty();
+        let home = user_home()?;
+
+        let caches = sys::get_user_dir(&home, SYSDIR_DIRECTORY_CACHES)?;
+        let application_support = sys::get_user_dir(&home, SYSDIR_DIRECTORY_APPLICATION_SUPPORT)?;
+
+        dirs.cache = caches;
+        // Apple puts config/data/state all in Application Support
+        dirs.config = application_support.clone();
+        dirs.data = application_support.clone();
+        dirs.state = application_support;
+
+        Ok(dirs)
+    }
+}
+
+#[unstable(feature = "media_dir_discovery", issue = "157515")]
+#[cfg(target_vendor = "apple")]
+impl MediaDirsExt for MediaDirs {
+    fn sysdir() -> io::Result<Self> {
+        use libc::sysdir_search_path_directory_t::*;
+
+        let mut dirs = MediaDirs::empty();
+        let home = user_home()?;
+
+        let desktop = sys::get_user_dir(&home, SYSDIR_DIRECTORY_DESKTOP)?;
+        let documents = sys::get_user_dir(&home, SYSDIR_DIRECTORY_DOCUMENT)?;
+        let downloads = sys::get_user_dir(&home, SYSDIR_DIRECTORY_DOWNLOADS)?;
+        let movies = sys::get_user_dir(&home, SYSDIR_DIRECTORY_MOVIES)?;
+        let music = sys::get_user_dir(&home, SYSDIR_DIRECTORY_MUSIC)?;
+        let pictures = sys::get_user_dir(&home, SYSDIR_DIRECTORY_PICTURES)?;
+
+        dirs.desktop = desktop;
+        dirs.documents = documents;
+        dirs.downloads = downloads;
+        dirs.music = music;
+        dirs.pictures = pictures;
+        dirs.videos = movies;
+
+        Ok(dirs)
+    }
+}
+
+/// Safer wrapper around the sysdir(3) API
+#[cfg(target_vendor = "apple")]
+mod sys {
+    use crate::ffi::{CStr, c_char};
+    use crate::io::{self, ErrorKind, const_error};
+    use crate::path::{Path, PathBuf};
+
+    /// Get the path for a system directory using `sysdir(3)`.
+    pub fn get_user_dir(
+        home: &Path,
+        kind: libc::sysdir_search_path_directory_t,
+    ) -> io::Result<Option<PathBuf>> {
+        use libc::sysdir_search_path_domain_mask_t::SYSDIR_DOMAIN_MASK_USER;
+
+        // SAFETY: SYSDIR_DOMAIN_MASK_USER < SYSDIR_DOMAIN_MASK_ALL
+        let mut iter = unsafe { Iter::new(home, kind, SYSDIR_DOMAIN_MASK_USER) };
+        let Some(path) = iter.next() else {
+            return Ok(None);
+        };
+
+        if iter.next().is_some() {
+            // more than one path returned (shouldn't happen for SYSDIR_DOMAIN_MASK_USER)
+            return Err(const_error!(
+                ErrorKind::InvalidData,
+                "multiple paths returned for standard user directory",
+            ));
+        }
+
+        Ok(Some(path?))
+    }
+
+    struct Iter<'a> {
+        home: &'a Path,
+        state: libc::sysdir_search_path_enumeration_state,
+    }
+
+    impl Drop for Iter<'_> {
+        fn drop(&mut self) {
+            for _ in self {}
+        }
+    }
+
+    impl<'a> Iter<'a> {
+        // SAFETY: `mask` must be <= `SYSDIR_DOMAIN_MASK_ALL`
+        pub unsafe fn new(
+            home: &'a Path,
+            kind: libc::sysdir_search_path_directory_t,
+            mask: libc::sysdir_search_path_domain_mask_t,
+        ) -> Self {
+            // SAFETY: forwarded to the caller
+            let state = unsafe { libc::sysdir_start_search_path_enumeration(kind, mask) };
+            Self { home, state }
+        }
+    }
+
+    impl Iterator for Iter<'_> {
+        type Item = io::Result<PathBuf>;
+
+        fn next(&mut self) -> Option<io::Result<PathBuf>> {
+            let mut buf = [0u8; libc::PATH_MAX as usize];
+            if self.state != 0 {
+                // SAFETY: `self.state` is nonzero and comes from prior sysdir_{start|get_next}_search_path_enumeration call
+                // SAFETY: sysdir_get_next_search_path_enumeration will write at most `PATH_MAX` bytes to `path`
+                self.state = unsafe {
+                    libc::sysdir_get_next_search_path_enumeration(
+                        self.state,
+                        buf.as_mut_ptr() as *mut c_char,
+                    )
+                };
+            }
+
+            if self.state == 0 {
+                // exhausted
+                return None;
+            }
+
+            let Ok(path) = CStr::from_bytes_until_nul(&buf) else {
+                // should be impossible given username length limits, but be defensive
+                return Some(Err(const_error!(
+                    ErrorKind::InvalidData,
+                    "standard user directory path too long",
+                )));
+            };
+
+            let Ok(path) = path.to_str() else {
+                // should be impossible on a working system, but be defensive
+                return Some(Err(const_error!(
+                    ErrorKind::InvalidData,
+                    "standard user directory path not valid UTF-8",
+                )));
+            };
+
+            // expand `~` shorthand
+            Some(match path {
+                "~" => Ok(self.home.into()),
+                _ if path.starts_with("~/") => Ok(self.home.join(&path[2..])),
+                _ if path.starts_with("~") => Err(const_error!(
+                    ErrorKind::InvalidData,
+                    "standard user directory relative to different user",
+                )),
+                _ => {
+                    let path = PathBuf::from(path);
+                    if path.is_relative() {
+                        Err(const_error!(
+                            ErrorKind::InvalidData,
+                            "standard user directory path not absolute",
+                        ))
+                    } else {
+                        Ok(path)
+                    }
+                }
+            })
+        }
+    }
+}
+
+#[cfg(test)]
+#[cfg(target_vendor = "apple")]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn can_fetch_sysdir_paths() {
+        let dirs = HomeDirs::sysdir().unwrap();
+        assert!(dirs.cache_home().is_some());
+        assert!(dirs.config_home().is_some());
+        assert!(dirs.data_home().is_some());
+        assert!(dirs.state_home().is_some());
+
+        let dirs = MediaDirs::sysdir().unwrap();
+        assert!(dirs.desktop().is_some());
+        assert!(dirs.documents().is_some());
+        assert!(dirs.downloads().is_some());
+        assert!(dirs.music().is_some());
+        assert!(dirs.pictures().is_some());
+        assert!(dirs.videos().is_some());
+    }
+}

library/std/src/os/unix/fs.rs

@@ -21,6 +21,13 @@ use crate::{io, sys};
 #[cfg(test)]
 mod tests;
 
+mod dirs;
+
+#[unstable(feature = "dir_discovery", issue = "157515")]
+pub use self::dirs::HomeDirsExt;
+#[unstable(feature = "media_dir_discovery", issue = "157515")]
+pub use self::dirs::MediaDirsExt;
+
 /// Unix-specific extensions to [`fs::File`].
 #[stable(feature = "file_offset", since = "1.15.0")]
 pub trait FileExt {