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    //! Various utilities for working with files and paths.

    use anyhow::{Context, Result};
    use filetime::FileTime;
    use std::env;
    use std::ffi::{OsStr, OsString};
    use std::fs::{self, File, Metadata, OpenOptions};
    use std::io;
    use std::io::prelude::*;
    use std::iter;
    use std::path::{Component, Path, PathBuf};
    use tempfile::Builder as TempFileBuilder;

    /// Joins paths into a string suitable for the `PATH` environment variable.
    ///
    /// This is equivalent to [`std::env::join_paths`], but includes a more
    /// detailed error message. The given `env` argument is the name of the
    /// environment variable this is will be used for, which is included in the
    /// error message.
    pub fn join_paths<T: AsRef<OsStr>>(paths: &[T], env: &str) -> Result<OsString> {
        env::join_paths(paths.iter()).with_context(|| {
            let mut message = format!(
                "failed to join paths from `${env}` together\n\n\
                 Check if any of path segments listed below contain an \
                 unterminated quote character or path separator:"
            );
            for path in paths {
                use std::fmt::Write;
                write!(&mut message, "\n    {:?}", Path::new(path)).unwrap();
            }

            message
        })
    }

    /// Returns the name of the environment variable used for searching for
    /// dynamic libraries.
    pub fn dylib_path_envvar() -> &'static str {
        if cfg!(windows) {
            "PATH"
        } else if cfg!(target_os = "macos") {
            // When loading and linking a dynamic library or bundle, dlopen
            // searches in LD_LIBRARY_PATH, DYLD_LIBRARY_PATH, PWD, and
            // DYLD_FALLBACK_LIBRARY_PATH.
            // In the Mach-O format, a dynamic library has an "install path."
            // Clients linking against the library record this path, and the
            // dynamic linker, dyld, uses it to locate the library.
            // dyld searches DYLD_LIBRARY_PATH *before* the install path.
            // dyld searches DYLD_FALLBACK_LIBRARY_PATH only if it cannot
            // find the library in the install path.
            // Setting DYLD_LIBRARY_PATH can easily have unintended
            // consequences.
            //
            // Also, DYLD_LIBRARY_PATH appears to have significant performance
            // penalty starting in 10.13. Cargo's testsuite ran more than twice as
            // slow with it on CI.
            "DYLD_FALLBACK_LIBRARY_PATH"
        } else if cfg!(target_os = "aix") {
            "LIBPATH"
        } else {
            "LD_LIBRARY_PATH"
        }
    }

    /// Returns a list of directories that are searched for dynamic libraries.
    ///
    /// Note that some operating systems will have defaults if this is empty that
    /// will need to be dealt with.
    pub fn dylib_path() -> Vec<PathBuf> {
        match env::var_os(dylib_path_envvar()) {
            Some(var) => env::split_paths(&var).collect(),
            None => Vec::new(),
        }
    }

    /// Normalize a path, removing things like `.` and `..`.
    ///
    /// CAUTION: This does not resolve symlinks (unlike
    /// [`std::fs::canonicalize`]). This may cause incorrect or surprising
    /// behavior at times. This should be used carefully. Unfortunately,
    /// [`std::fs::canonicalize`] can be hard to use correctly, since it can often
    /// fail, or on Windows returns annoying device paths. This is a problem Cargo
    /// needs to improve on.
    pub fn normalize_path(path: &Path) -> PathBuf {
        let mut components = path.components().peekable();
        let mut ret = if let Some(c @ Component::Prefix(..)) = components.peek().cloned() {
            components.next();
            PathBuf::from(c.as_os_str())
        } else {
            PathBuf::new()
        };

        for component in components {
            match component {
                Component::Prefix(..) => unreachable!(),
                Component::RootDir => {
                    ret.push(component.as_os_str());
                }
                Component::CurDir => {}
                Component::ParentDir => {
                    ret.pop();
                }
                Component::Normal(c) => {
                    ret.push(c);
                }
            }
        }
        ret
    }

    /// Returns the absolute path of where the given executable is located based
    /// on searching the `PATH` environment variable.
    ///
    /// Returns an error if it cannot be found.
    pub fn resolve_executable(exec: &Path) -> Result<PathBuf> {
        if exec.components().count() == 1 {
            let paths = env::var_os("PATH").ok_or_else(|| anyhow::format_err!("no PATH"))?;
            let candidates = env::split_paths(&paths).flat_map(|path| {
                let candidate = path.join(&exec);
                let with_exe = if env::consts::EXE_EXTENSION.is_empty() {
                    None
                } else {
                    Some(candidate.with_extension(env::consts::EXE_EXTENSION))
                };
                iter::once(candidate).chain(with_exe)
            });
            for candidate in candidates {
                if candidate.is_file() {
                    return Ok(candidate);
                }
            }

            anyhow::bail!("no executable for `{}` found in PATH", exec.display())
        } else {
            Ok(exec.into())
        }
    }

    /// Returns metadata for a file (follows symlinks).
    ///
    /// Equivalent to [`std::fs::metadata`] with better error messages.
    pub fn metadata<P: AsRef<Path>>(path: P) -> Result<Metadata> {
        let path = path.as_ref();
        std::fs::metadata(path)
            .with_context(|| format!("failed to load metadata for path `{}`", path.display()))
    }

    /// Returns metadata for a file without following symlinks.
    ///
    /// Equivalent to [`std::fs::metadata`] with better error messages.
    pub fn symlink_metadata<P: AsRef<Path>>(path: P) -> Result<Metadata> {
        let path = path.as_ref();
        std::fs::symlink_metadata(path)
            .with_context(|| format!("failed to load metadata for path `{}`", path.display()))
    }

    /// Reads a file to a string.
    ///
    /// Equivalent to [`std::fs::read_to_string`] with better error messages.
    pub fn read(path: &Path) -> Result<String> {
        match String::from_utf8(read_bytes(path)?) {
            Ok(s) => Ok(s),
            Err(_) => anyhow::bail!("path at `{}` was not valid utf-8", path.display()),
        }
    }

    /// Reads a file into a bytes vector.
    ///
    /// Equivalent to [`std::fs::read`] with better error messages.
    pub fn read_bytes(path: &Path) -> Result<Vec<u8>> {
        fs::read(path).with_context(|| format!("failed to read `{}`", path.display()))
    }

    /// Writes a file to disk.
    ///
    /// Equivalent to [`std::fs::write`] with better error messages.
    pub fn write<P: AsRef<Path>, C: AsRef<[u8]>>(path: P, contents: C) -> Result<()> {
        let path = path.as_ref();
        fs::write(path, contents.as_ref())
            .with_context(|| format!("failed to write `{}`", path.display()))
    }

    /// Writes a file to disk atomically.
    ///
    /// write_atomic uses tempfile::persist to accomplish atomic writes.
    pub fn write_atomic<P: AsRef<Path>, C: AsRef<[u8]>>(path: P, contents: C) -> Result<()> {
        let path = path.as_ref();
        let mut tmp = TempFileBuilder::new()
            .prefix(path.file_name().unwrap())
            .tempfile_in(path.parent().unwrap())?;
        tmp.write_all(contents.as_ref())?;
        tmp.persist(path)?;
        Ok(())
    }

    /// Equivalent to [`write()`], but does not write anything if the file contents
    /// are identical to the given contents.
    pub fn write_if_changed<P: AsRef<Path>, C: AsRef<[u8]>>(path: P, contents: C) -> Result<()> {
        (|| -> Result<()> {
            let contents = contents.as_ref();
            let mut f = OpenOptions::new()
                .read(true)
                .write(true)
                .create(true)
                .open(&path)?;
            let mut orig = Vec::new();
            f.read_to_end(&mut orig)?;
            if orig != contents {
                f.set_len(0)?;
                f.seek(io::SeekFrom::Start(0))?;
                f.write_all(contents)?;
            }
            Ok(())
        })()
        .with_context(|| format!("failed to write `{}`", path.as_ref().display()))?;
        Ok(())
    }

    /// Equivalent to [`write()`], but appends to the end instead of replacing the
    /// contents.
    pub fn append(path: &Path, contents: &[u8]) -> Result<()> {
        (|| -> Result<()> {
            let mut f = OpenOptions::new()
                .write(true)
                .append(true)
                .create(true)
                .open(path)?;

            f.write_all(contents)?;
            Ok(())
        })()
        .with_context(|| format!("failed to write `{}`", path.display()))?;
        Ok(())
    }

    /// Creates a new file.
    pub fn create<P: AsRef<Path>>(path: P) -> Result<File> {
        let path = path.as_ref();
        File::create(path).with_context(|| format!("failed to create file `{}`", path.display()))
    }

    /// Opens an existing file.
    pub fn open<P: AsRef<Path>>(path: P) -> Result<File> {
        let path = path.as_ref();
        File::open(path).with_context(|| format!("failed to open file `{}`", path.display()))
    }

    /// Returns the last modification time of a file.
    pub fn mtime(path: &Path) -> Result<FileTime> {
        let meta = metadata(path)?;
        Ok(FileTime::from_last_modification_time(&meta))
    }

    /// Returns the maximum mtime of the given path, recursing into
    /// subdirectories, and following symlinks.
    pub fn mtime_recursive(path: &Path) -> Result<FileTime> {
        let meta = metadata(path)?;
        if !meta.is_dir() {
            return Ok(FileTime::from_last_modification_time(&meta));
        }
        let max_meta = walkdir::WalkDir::new(path)
            .follow_links(true)
            .into_iter()
            .filter_map(|e| match e {
                Ok(e) => Some(e),
                Err(e) => {
                    // Ignore errors while walking. If Cargo can't access it, the
                    // build script probably can't access it, either.
                    tracing::debug!("failed to determine mtime while walking directory: {}", e);
                    None
                }
            })
            .filter_map(|e| {
                if e.path_is_symlink() {
                    // Use the mtime of both the symlink and its target, to
                    // handle the case where the symlink is modified to a
                    // different target.
                    let sym_meta = match std::fs::symlink_metadata(e.path()) {
                        Ok(m) => m,
                        Err(err) => {
                            // I'm not sure when this is really possible (maybe a
                            // race with unlinking?). Regardless, if Cargo can't
                            // read it, the build script probably can't either.
                            tracing::debug!(
                                "failed to determine mtime while fetching symlink metadata of {}: {}",
                                e.path().display(),
                                err
                            );
                            return None;
                        }
                    };
                    let sym_mtime = FileTime::from_last_modification_time(&sym_meta);
                    // Walkdir follows symlinks.
                    match e.metadata() {
                        Ok(target_meta) => {
                            let target_mtime = FileTime::from_last_modification_time(&target_meta);
                            Some(sym_mtime.max(target_mtime))
                        }
                        Err(err) => {
                            // Can't access the symlink target. If Cargo can't
                            // access it, the build script probably can't access
                            // it either.
                            tracing::debug!(
                                "failed to determine mtime of symlink target for {}: {}",
                                e.path().display(),
                                err
                            );
                            Some(sym_mtime)
                        }
                    }
                } else {
                    let meta = match e.metadata() {
                        Ok(m) => m,
                        Err(err) => {
                            // I'm not sure when this is really possible (maybe a
                            // race with unlinking?). Regardless, if Cargo can't
                            // read it, the build script probably can't either.
                            tracing::debug!(
                                "failed to determine mtime while fetching metadata of {}: {}",
                                e.path().display(),
                                err
                            );
                            return None;
                        }
                    };
                    Some(FileTime::from_last_modification_time(&meta))
                }
            })
            .max()
            // or_else handles the case where there are no files in the directory.
            .unwrap_or_else(|| FileTime::from_last_modification_time(&meta));
        Ok(max_meta)
    }

    /// Record the current time on the filesystem (using the filesystem's clock)
    /// using a file at the given directory. Returns the current time.
    pub fn set_invocation_time(path: &Path) -> Result<FileTime> {
        // note that if `FileTime::from_system_time(SystemTime::now());` is determined to be sufficient,
        // then this can be removed.
        let timestamp = path.join("invoked.timestamp");
        write(
            &timestamp,
            "This file has an mtime of when this was started.",
        )?;
        let ft = mtime(&timestamp)?;
        tracing::debug!("invocation time for {:?} is {}", path, ft);
        Ok(ft)
    }

    /// Converts a path to UTF-8 bytes.
    pub fn path2bytes(path: &Path) -> Result<&[u8]> {
        #[cfg(unix)]
        {
            use std::os::unix::prelude::*;
            Ok(path.as_os_str().as_bytes())
        }
        #[cfg(windows)]
        {
            match path.as_os_str().to_str() {
                Some(s) => Ok(s.as_bytes()),
                None => Err(anyhow::format_err!(
                    "invalid non-unicode path: {}",
                    path.display()
                )),
            }
        }
    }

    /// Converts UTF-8 bytes to a path.
    pub fn bytes2path(bytes: &[u8]) -> Result<PathBuf> {
        #[cfg(unix)]
        {
            use std::os::unix::prelude::*;
            Ok(PathBuf::from(OsStr::from_bytes(bytes)))
        }
        #[cfg(windows)]
        {
            use std::str;
            match str::from_utf8(bytes) {
                Ok(s) => Ok(PathBuf::from(s)),
                Err(..) => Err(anyhow::format_err!("invalid non-unicode path")),
            }
        }
    }

    /// Returns an iterator that walks up the directory hierarchy towards the root.
    ///
    /// Each item is a [`Path`]. It will start with the given path, finishing at
    /// the root. If the `stop_root_at` parameter is given, it will stop at the
    /// given path (which will be the last item).
    pub fn ancestors<'a>(path: &'a Path, stop_root_at: Option<&Path>) -> PathAncestors<'a> {
        PathAncestors::new(path, stop_root_at)
    }

    pub struct PathAncestors<'a> {
        current: Option<&'a Path>,
        stop_at: Option<PathBuf>,
    }

    impl<'a> PathAncestors<'a> {
        fn new(path: &'a Path, stop_root_at: Option<&Path>) -> PathAncestors<'a> {
            let stop_at = env::var("__CARGO_TEST_ROOT")
                .ok()
                .map(PathBuf::from)
                .or_else(|| stop_root_at.map(|p| p.to_path_buf()));
            PathAncestors {
                current: Some(path),
                //HACK: avoid reading `~/.cargo/config` when testing Cargo itself.
                stop_at,
            }
        }
    }

    impl<'a> Iterator for PathAncestors<'a> {
        type Item = &'a Path;

        fn next(&mut self) -> Option<&'a Path> {
            if let Some(path) = self.current {
                self.current = path.parent();

                if let Some(ref stop_at) = self.stop_at {
                    if path == stop_at {
                        self.current = None;
                    }
                }

                Some(path)
            } else {
                None
            }
        }
    }

    /// Equivalent to [`std::fs::create_dir_all`] with better error messages.
    pub fn create_dir_all(p: impl AsRef<Path>) -> Result<()> {
        _create_dir_all(p.as_ref())
    }

    fn _create_dir_all(p: &Path) -> Result<()> {
        fs::create_dir_all(p)
            .with_context(|| format!("failed to create directory `{}`", p.display()))?;
        Ok(())
    }

    /// Equivalent to [`std::fs::remove_dir_all`] with better error messages.
    ///
    /// This does *not* follow symlinks.
    pub fn remove_dir_all<P: AsRef<Path>>(p: P) -> Result<()> {
        _remove_dir_all(p.as_ref()).or_else(|prev_err| {
            // `std::fs::remove_dir_all` is highly specialized for different platforms
            // and may be more reliable than a simple walk. We try the walk first in
            // order to report more detailed errors.
            fs::remove_dir_all(p.as_ref()).with_context(|| {
                format!(
                    "{:?}\n\nError: failed to remove directory `{}`",
                    prev_err,
                    p.as_ref().display(),
                )
            })
        })
    }

    fn _remove_dir_all(p: &Path) -> Result<()> {
        if symlink_metadata(p)?.is_symlink() {
            return remove_file(p);
        }
        let entries = p
            .read_dir()
            .with_context(|| format!("failed to read directory `{}`", p.display()))?;
        for entry in entries {
            let entry = entry?;
            let path = entry.path();
            if entry.file_type()?.is_dir() {
                remove_dir_all(&path)?;
            } else {
                remove_file(&path)?;
            }
        }
        remove_dir(&p)
    }

    /// Equivalent to [`std::fs::remove_dir`] with better error messages.
    pub fn remove_dir<P: AsRef<Path>>(p: P) -> Result<()> {
        _remove_dir(p.as_ref())
    }

    fn _remove_dir(p: &Path) -> Result<()> {
        fs::remove_dir(p).with_context(|| format!("failed to remove directory `{}`", p.display()))?;
        Ok(())
    }

    /// Equivalent to [`std::fs::remove_file`] with better error messages.
    ///
    /// If the file is readonly, this will attempt to change the permissions to
    /// force the file to be deleted.
    pub fn remove_file<P: AsRef<Path>>(p: P) -> Result<()> {
        _remove_file(p.as_ref())
    }

    fn _remove_file(p: &Path) -> Result<()> {
        let mut err = match fs::remove_file(p) {
            Ok(()) => return Ok(()),
            Err(e) => e,
        };

        if err.kind() == io::ErrorKind::PermissionDenied && set_not_readonly(p).unwrap_or(false) {
            match fs::remove_file(p) {
                Ok(()) => return Ok(()),
                Err(e) => err = e,
            }
        }

        Err(err).with_context(|| format!("failed to remove file `{}`", p.display()))?;
        Ok(())
    }

    fn set_not_readonly(p: &Path) -> io::Result<bool> {
        let mut perms = p.metadata()?.permissions();
        if !perms.readonly() {
            return Ok(false);
        }
        perms.set_readonly(false);
        fs::set_permissions(p, perms)?;
        Ok(true)
    }

    /// Hardlink (file) or symlink (dir) src to dst if possible, otherwise copy it.
    ///
    /// If the destination already exists, it is removed before linking.
    pub fn link_or_copy(src: impl AsRef<Path>, dst: impl AsRef<Path>) -> Result<()> {
        let src = src.as_ref();
        let dst = dst.as_ref();
        _link_or_copy(src, dst)
    }

    fn _link_or_copy(src: &Path, dst: &Path) -> Result<()> {
        tracing::debug!("linking {} to {}", src.display(), dst.display());
        if same_file::is_same_file(src, dst).unwrap_or(false) {
            return Ok(());
        }

        // NB: we can't use dst.exists(), as if dst is a broken symlink,
        // dst.exists() will return false. This is problematic, as we still need to
        // unlink dst in this case. symlink_metadata(dst).is_ok() will tell us
        // whether dst exists *without* following symlinks, which is what we want.
        if fs::symlink_metadata(dst).is_ok() {
            remove_file(&dst)?;
        }

        let link_result = if src.is_dir() {
            #[cfg(target_os = "redox")]
            use std::os::redox::fs::symlink;
            #[cfg(unix)]
            use std::os::unix::fs::symlink;
            #[cfg(windows)]
            // FIXME: This should probably panic or have a copy fallback. Symlinks
            // are not supported in all windows environments. Currently symlinking
            // is only used for .dSYM directories on macos, but this shouldn't be
            // accidentally relied upon.
            use std::os::windows::fs::symlink_dir as symlink;

            let dst_dir = dst.parent().unwrap();
            let src = if src.starts_with(dst_dir) {
                src.strip_prefix(dst_dir).unwrap()
            } else {
                src
            };
            symlink(src, dst)
        } else if env::var_os("__CARGO_COPY_DONT_LINK_DO_NOT_USE_THIS").is_some() {
            // This is a work-around for a bug in macOS 10.15. When running on
            // APFS, there seems to be a strange race condition with
            // Gatekeeper where it will forcefully kill a process launched via
            // `cargo run` with SIGKILL. Copying seems to avoid the problem.
            // This shouldn't affect anyone except Cargo's test suite because
            // it is very rare, and only seems to happen under heavy load and
            // rapidly creating lots of executables and running them.
            // See https://github.com/rust-lang/cargo/issues/7821 for the
            // gory details.
            fs::copy(src, dst).map(|_| ())
        } else {
            if cfg!(target_os = "macos") {
                // This is a work-around for a bug on macos. There seems to be a race condition
                // with APFS when hard-linking binaries. Gatekeeper does not have signing or
                // hash information stored in kernel when running the process. Therefore killing it.
                // This problem does not appear when copying files as kernel has time to process it.
                // Note that: fs::copy on macos is using CopyOnWrite (syscall fclonefileat) which should be
                // as fast as hardlinking.
                // See https://github.com/rust-lang/cargo/issues/10060 for the details
                fs::copy(src, dst).map(|_| ())
            } else {
                fs::hard_link(src, dst)
            }
        };
        link_result
            .or_else(|err| {
                tracing::debug!("link failed {}. falling back to fs::copy", err);
                fs::copy(src, dst).map(|_| ())
            })
            .with_context(|| {
                format!(
                    "failed to link or copy `{}` to `{}`",
                    src.display(),
                    dst.display()
                )
            })?;
        Ok(())
    }

    /// Copies a file from one location to another.
    ///
    /// Equivalent to [`std::fs::copy`] with better error messages.
    pub fn copy<P: AsRef<Path>, Q: AsRef<Path>>(from: P, to: Q) -> Result<u64> {
        let from = from.as_ref();
        let to = to.as_ref();
        fs::copy(from, to)
            .with_context(|| format!("failed to copy `{}` to `{}`", from.display(), to.display()))
    }

    /// Changes the filesystem mtime (and atime if possible) for the given file.
    ///
    /// This intentionally does not return an error, as this is sometimes not
    /// supported on network filesystems. For the current uses in Cargo, this is a
    /// "best effort" approach, and errors shouldn't be propagated.
    pub fn set_file_time_no_err<P: AsRef<Path>>(path: P, time: FileTime) {
        let path = path.as_ref();
        match filetime::set_file_times(path, time, time) {
            Ok(()) => tracing::debug!("set file mtime {} to {}", path.display(), time),
            Err(e) => tracing::warn!(
                "could not set mtime of {} to {}: {:?}",
                path.display(),
                time,
                e
            ),
        }
    }

    /// Strips `base` from `path`.
    ///
    /// This canonicalizes both paths before stripping. This is useful if the
    /// paths are obtained in different ways, and one or the other may or may not
    /// have been normalized in some way.
    pub fn strip_prefix_canonical<P: AsRef<Path>>(
        path: P,
        base: P,
    ) -> Result<PathBuf, std::path::StripPrefixError> {
        // Not all filesystems support canonicalize. Just ignore if it doesn't work.
        let safe_canonicalize = |path: &Path| match path.canonicalize() {
            Ok(p) => p,
            Err(e) => {
                tracing::warn!("cannot canonicalize {:?}: {:?}", path, e);
                path.to_path_buf()
            }
        };
        let canon_path = safe_canonicalize(path.as_ref());
        let canon_base = safe_canonicalize(base.as_ref());
        canon_path.strip_prefix(canon_base).map(|p| p.to_path_buf())
    }

    /// Creates an excluded from cache directory atomically with its parents as needed.
    ///
    /// The atomicity only covers creating the leaf directory and exclusion from cache. Any missing
    /// parent directories will not be created in an atomic manner.
    ///
    /// This function is idempotent and in addition to that it won't exclude ``p`` from cache if it
    /// already exists.
    pub fn create_dir_all_excluded_from_backups_atomic(p: impl AsRef<Path>) -> Result<()> {
        let path = p.as_ref();
        if path.is_dir() {
            return Ok(());
        }

        let parent = path.parent().unwrap();
        let base = path.file_name().unwrap();
        create_dir_all(parent)?;
        // We do this in two steps (first create a temporary directory and exclude
        // it from backups, then rename it to the desired name. If we created the
        // directory directly where it should be and then excluded it from backups
        // we would risk a situation where cargo is interrupted right after the directory
        // creation but before the exclusion the directory would remain non-excluded from
        // backups because we only perform exclusion right after we created the directory
        // ourselves.
        //
        // We need the tempdir created in parent instead of $TMP, because only then we can be
        // easily sure that rename() will succeed (the new name needs to be on the same mount
        // point as the old one).
        let tempdir = TempFileBuilder::new().prefix(base).tempdir_in(parent)?;
        exclude_from_backups(tempdir.path());
        exclude_from_content_indexing(tempdir.path());
        // Previously std::fs::create_dir_all() (through paths::create_dir_all()) was used
        // here to create the directory directly and fs::create_dir_all() explicitly treats
        // the directory being created concurrently by another thread or process as success,
        // hence the check below to follow the existing behavior. If we get an error at
        // rename() and suddenly the directory (which didn't exist a moment earlier) exists
        // we can infer from it's another cargo process doing work.
        if let Err(e) = fs::rename(tempdir.path(), path) {
            if !path.exists() {
                return Err(anyhow::Error::from(e))
                    .with_context(|| format!("failed to create directory `{}`", path.display()));
            }
        }
        Ok(())
    }

    /// Mark an existing directory as excluded from backups and indexing.
    ///
    /// Errors in marking it are ignored.
    pub fn exclude_from_backups_and_indexing(p: impl AsRef<Path>) {
        let path = p.as_ref();
        exclude_from_backups(path);
        exclude_from_content_indexing(path);
    }

    /// Marks the directory as excluded from archives/backups.
    ///
    /// This is recommended to prevent derived/temporary files from bloating backups. There are two
    /// mechanisms used to achieve this right now:
    ///
    /// * A dedicated resource property excluding from Time Machine backups on macOS
    /// * CACHEDIR.TAG files supported by various tools in a platform-independent way
    fn exclude_from_backups(path: &Path) {
        exclude_from_time_machine(path);
        let file = path.join("CACHEDIR.TAG");
        if !file.exists() {
            let _ = std::fs::write(
                file,
                "Signature: 8a477f597d28d172789f06886806bc55
    # This file is a cache directory tag created by cargo.
    # For information about cache directory tags see https://bford.info/cachedir/
    ",
            );
            // Similarly to exclude_from_time_machine() we ignore errors here as it's an optional feature.
        }
    }

    /// Marks the directory as excluded from content indexing.
    ///
    /// This is recommended to prevent the content of derived/temporary files from being indexed.
    /// This is very important for Windows users, as the live content indexing significantly slows
    /// cargo's I/O operations.
    ///
    /// This is currently a no-op on non-Windows platforms.
    fn exclude_from_content_indexing(path: &Path) {
        #[cfg(windows)]
        {
            use std::iter::once;
            use std::os::windows::prelude::OsStrExt;
            use windows_sys::Win32::Storage::FileSystem::{
                GetFileAttributesW, SetFileAttributesW, FILE_ATTRIBUTE_NOT_CONTENT_INDEXED,
            };

            let path: Vec<u16> = path.as_os_str().encode_wide().chain(once(0)).collect();
            unsafe {
                SetFileAttributesW(
                    path.as_ptr(),
                    GetFileAttributesW(path.as_ptr()) | FILE_ATTRIBUTE_NOT_CONTENT_INDEXED,
                );
            }
        }
        #[cfg(not(windows))]
        {
            let _ = path;
        }
    }

    #[cfg(not(target_os = "macos"))]
    fn exclude_from_time_machine(_: &Path) {}

    #[cfg(target_os = "macos")]
    /// Marks files or directories as excluded from Time Machine on macOS
    fn exclude_from_time_machine(path: &Path) {
        use core_foundation::base::TCFType;
        use core_foundation::{number, string, url};
        use std::ptr;

        // For compatibility with 10.7 a string is used instead of global kCFURLIsExcludedFromBackupKey
        let is_excluded_key: Result<string::CFString, _> = "NSURLIsExcludedFromBackupKey".parse();
        let path = url::CFURL::from_path(path, false);
        if let (Some(path), Ok(is_excluded_key)) = (path, is_excluded_key) {
            unsafe {
                url::CFURLSetResourcePropertyForKey(
                    path.as_concrete_TypeRef(),
                    is_excluded_key.as_concrete_TypeRef(),
                    number::kCFBooleanTrue as *const _,
                    ptr::null_mut(),
                );
            }
        }
        // Errors are ignored, since it's an optional feature and failure
        // doesn't prevent Cargo from working
    }

    #[cfg(test)]
    mod tests {
        use super::join_paths;
        use super::write;
        use super::write_atomic;

        #[test]
        fn write_works() {
            let original_contents = "[dependencies]\nfoo = 0.1.0";

            let tmpdir = tempfile::tempdir().unwrap();
            let path = tmpdir.path().join("Cargo.toml");
            write(&path, original_contents).unwrap();
            let contents = std::fs::read_to_string(&path).unwrap();
            assert_eq!(contents, original_contents);
        }
        #[test]
        fn write_atomic_works() {
            let original_contents = "[dependencies]\nfoo = 0.1.0";

            let tmpdir = tempfile::tempdir().unwrap();
            let path = tmpdir.path().join("Cargo.toml");
            write_atomic(&path, original_contents).unwrap();
            let contents = std::fs::read_to_string(&path).unwrap();
            assert_eq!(contents, original_contents);
        }

        #[test]
        fn join_paths_lists_paths_on_error() {
            let valid_paths = vec!["/testing/one", "/testing/two"];
            // does not fail on valid input
            let _joined = join_paths(&valid_paths, "TESTING1").unwrap();

            #[cfg(unix)]
            {
                let invalid_paths = vec!["/testing/one", "/testing/t:wo/three"];
                let err = join_paths(&invalid_paths, "TESTING2").unwrap_err();
                assert_eq!(
                    err.to_string(),
                    "failed to join paths from `$TESTING2` together\n\n\
                 Check if any of path segments listed below contain an \
                 unterminated quote character or path separator:\
                 \n    \"/testing/one\"\
                 \n    \"/testing/t:wo/three\"\
                 "
                );
            }
            #[cfg(windows)]
            {
                let invalid_paths = vec!["/testing/one", "/testing/t\"wo/three"];
                let err = join_paths(&invalid_paths, "TESTING2").unwrap_err();
                assert_eq!(
                    err.to_string(),
                    "failed to join paths from `$TESTING2` together\n\n\
                 Check if any of path segments listed below contain an \
                 unterminated quote character or path separator:\
                 \n    \"/testing/one\"\
                 \n    \"/testing/t\\\"wo/three\"\
                 "
                );
            }
        }
    }