feat: add the ability to override the default temporary directory

CHANGELOG.md

@@ -1,5 +1,9 @@
 # Changelog
 
+## 3.11.0
+
+- Add the ability to override the default temporary directory. This API shouldn't be used in general, but there are some cases where it's unavoidable.
+
 ## 3.10.1
 
 - Handle potential integer overflows in 32-bit systems when seeking/truncating "spooled" temporary files past 4GiB (2³²).

Cargo.toml

@@ -19,6 +19,8 @@ description = "A library for managing temporary files and directories."
 [dependencies]
 cfg-if = "1"
 fastrand = "2.0.1"
+# Not available in stdlib until 1.70, but we support 1.63 to support Debian stable.
+once_cell = { version = "1.19.0", default-features = false, features = ["std"] }
 
 [target.'cfg(any(unix, target_os = "wasi"))'.dependencies]
 rustix = { version = "0.38.31", features = ["fs"] }

src/dir/mod.rs

@@ -17,6 +17,9 @@ use std::{fmt, io};
 use crate::error::IoResultExt;
 use crate::Builder;
 
+#[cfg(doc)]
+use crate::env;
+
 /// Create a new temporary directory.
 ///
 /// The `tempdir` function creates a directory in the file system
@@ -39,7 +42,7 @@ use crate::Builder;
 /// use std::fs::File;
 /// use std::io::Write;
 ///
-/// // Create a directory inside of `std::env::temp_dir()`
+/// // Create a directory inside of `env::temp_dir()`
 /// let tmp_dir = tempdir()?;
 ///
 /// let file_path = tmp_dir.path().join("my-temporary-note.txt");
@@ -109,7 +112,7 @@ pub fn tempdir_in<P: AsRef<Path>>(dir: P) -> io::Result<TempDir> {
 /// `TempDir` creates a new directory with a randomly generated name.
 ///
 /// The default constructor, [`TempDir::new()`], creates directories in
-/// the location returned by [`std::env::temp_dir()`], but `TempDir`
+/// the location returned by [`env::temp_dir()`], but `TempDir`
 /// can be configured to manage a temporary directory in any location
 /// by constructing with a [`Builder`].
 ///
@@ -144,7 +147,7 @@ pub fn tempdir_in<P: AsRef<Path>>(dir: P) -> io::Result<TempDir> {
 /// use std::io::Write;
 /// use tempfile::TempDir;
 ///
-/// // Create a directory inside of `std::env::temp_dir()`
+/// // Create a directory inside of `env::temp_dir()`
 /// let tmp_dir = TempDir::new()?;
 /// # Ok::<(), std::io::Error>(())
 /// ```
@@ -156,7 +159,7 @@ pub fn tempdir_in<P: AsRef<Path>>(dir: P) -> io::Result<TempDir> {
 /// use std::io::Write;
 /// use tempfile::Builder;
 ///
-/// // Create a directory inside of `std::env::temp_dir()`,
+/// // Create a directory inside of `env::temp_dir()`,
 /// // whose name will begin with 'example'.
 /// let tmp_dir = Builder::new().prefix("example").tempdir()?;
 /// # Ok::<(), std::io::Error>(())
@@ -170,7 +173,6 @@ pub fn tempdir_in<P: AsRef<Path>>(dir: P) -> io::Result<TempDir> {
 /// [`TempDir::new()`]: struct.TempDir.html#method.new
 /// [`TempDir::path()`]: struct.TempDir.html#method.path
 /// [`TempDir`]: struct.TempDir.html
-/// [`std::env::temp_dir()`]: https://doc.rust-lang.org/std/env/fn.temp_dir.html
 /// [`std::fs`]: http://doc.rust-lang.org/std/fs/index.html
 /// [`std::process::exit()`]: http://doc.rust-lang.org/std/process/fn.exit.html
 pub struct TempDir {
@@ -196,7 +198,7 @@ impl TempDir {
     /// use std::io::Write;
     /// use tempfile::TempDir;
     ///
-    /// // Create a directory inside of `std::env::temp_dir()`
+    /// // Create a directory inside of `env::temp_dir()`
     /// let tmp_dir = TempDir::new()?;
     ///
     /// let file_path = tmp_dir.path().join("my-temporary-note.txt");
@@ -378,7 +380,7 @@ impl TempDir {
     /// use std::io::Write;
     /// use tempfile::TempDir;
     ///
-    /// // Create a directory inside of `std::env::temp_dir()`.
+    /// // Create a directory inside of `env::temp_dir()`.
     /// let tmp_dir = TempDir::new()?;
     /// let file_path = tmp_dir.path().join("my-temporary-note.txt");
     /// let mut tmp_file = File::create(file_path)?;

src/env.rs

@@ -0,0 +1,43 @@
+use std::env;
+use std::path::{Path, PathBuf};
+
+// Once rust 1.70 is wide-spread (Debian stable), we can use OnceLock from stdlib.
+use once_cell::sync::OnceCell as OnceLock;
+
+static DEFAULT_TEMPDIR: OnceLock<PathBuf> = OnceLock::new();
+
+/// Override the default temporary directory (defaults to [`std::env::temp_dir`]). This function
+/// changes the _global_ default temporary directory for the entire program and should not be called
+/// except in exceptional cases where it's not configured correctly by the platform.
+///
+/// Only the first call to this function will succeed. All further calls will fail with `Err(path)`
+/// where `path` is previously set default temporary directory override.
+///
+/// **NOTE:** This function does not check if the specified directory exists and/or is writable.
+pub fn override_temp_dir(path: &Path) -> Result<(), PathBuf> {
+    let mut we_set = false;
+    let val = DEFAULT_TEMPDIR.get_or_init(|| {
+        we_set = true;
+        path.to_path_buf()
+    });
+    if we_set {
+        Ok(())
+    } else {
+        Err(val.to_owned())
+    }
+}
+
+/// Returns the default temporary directory, used for both temporary directories and files if no
+/// directory is explicitly specified.
+///
+/// This function simply delegates to [`std::env::temp_dir`] unless the default temporary directory
+/// has been override by a call to [`override_temp_dir`].
+///
+/// **NOTE:** This function does check if the returned directory exists and/or is writable.
+pub fn temp_dir() -> PathBuf {
+    DEFAULT_TEMPDIR
+        .get()
+        .map(|p| p.to_owned())
+        // Don't cache this in case the user uses std::env::set to change the temporary directory.
+        .unwrap_or_else(env::temp_dir)
+}

src/file/imp/unix.rs

@@ -1,4 +1,3 @@
-use std::env;
 use std::ffi::OsStr;
 use std::fs::{self, File, OpenOptions};
 use std::io;
@@ -40,7 +39,7 @@ fn create_unlinked(path: &Path) -> io::Result<File> {
     // shadow this to decrease the lifetime. It can't live longer than `tmp`.
     let mut path = path;
     if !path.is_absolute() {
-        let cur_dir = env::current_dir()?;
+        let cur_dir = std::env::current_dir()?;
         tmp = cur_dir.join(path);
         path = &tmp;
     }

src/file/mod.rs

@@ -1,4 +1,3 @@
-use std::env;
 use std::error;
 use std::ffi::OsStr;
 use std::fmt;
@@ -14,14 +13,15 @@ use std::os::wasi::io::{AsFd, AsRawFd, BorrowedFd, RawFd};
 use std::os::windows::io::{AsHandle, AsRawHandle, BorrowedHandle, RawHandle};
 use std::path::{Path, PathBuf};
 
+use crate::env;
 use crate::error::IoResultExt;
 use crate::Builder;
 
 mod imp;
 
 /// Create a new temporary file.
 ///
-/// The file will be created in the location returned by [`std::env::temp_dir()`].
+/// The file will be created in the location returned by [`env::temp_dir()`].
 ///
 /// # Security
 ///
@@ -42,14 +42,12 @@ mod imp;
 /// use tempfile::tempfile;
 /// use std::io::Write;
 ///
-/// // Create a file inside of `std::env::temp_dir()`.
+/// // Create a file inside of `env::temp_dir()`.
 /// let mut file = tempfile()?;
 ///
 /// writeln!(file, "Brian was here. Briefly.")?;
 /// # Ok::<(), std::io::Error>(())
 /// ```
-///
-/// [`std::env::temp_dir()`]: https://doc.rust-lang.org/std/env/fn.temp_dir.html
 pub fn tempfile() -> io::Result<File> {
     tempfile_in(env::temp_dir())
 }
@@ -59,7 +57,7 @@ pub fn tempfile() -> io::Result<File> {
 /// # Security
 ///
 /// This variant is secure/reliable in the presence of a pathological temporary file cleaner.
-/// If the temporary file isn't created in [`std::env::temp_dir()`] then temporary file cleaners aren't an issue.
+/// If the temporary file isn't created in [`env::temp_dir()`] then temporary file cleaners aren't an issue.
 ///
 /// # Resource Leaking
 ///
@@ -82,8 +80,6 @@ pub fn tempfile() -> io::Result<File> {
 /// writeln!(file, "Brian was here. Briefly.")?;
 /// # Ok::<(), std::io::Error>(())
 /// ```
-///
-/// [`std::env::temp_dir()`]: https://doc.rust-lang.org/std/env/fn.temp_dir.html
 pub fn tempfile_in<P: AsRef<Path>>(dir: P) -> io::Result<File> {
     imp::create(dir.as_ref())
 }
@@ -363,7 +359,7 @@ impl AsRef<OsStr> for TempPath {
 /// A named temporary file.
 ///
 /// The default constructor, [`NamedTempFile::new()`], creates files in
-/// the location returned by [`std::env::temp_dir()`], but `NamedTempFile`
+/// the location returned by [`env::temp_dir()`], but `NamedTempFile`
 /// can be configured to manage a temporary file in any location
 /// by constructing with [`NamedTempFile::new_in()`].
 ///
@@ -440,7 +436,6 @@ impl AsRef<OsStr> for TempPath {
 /// [`tempfile()`]: fn.tempfile.html
 /// [`NamedTempFile::new()`]: #method.new
 /// [`NamedTempFile::new_in()`]: #method.new_in
-/// [`std::env::temp_dir()`]: https://doc.rust-lang.org/std/env/fn.temp_dir.html
 /// [`std::process::exit()`]: http://doc.rust-lang.org/std/process/fn.exit.html
 /// [`lazy_static`]: https://github.com/rust-lang-nursery/lazy-static.rs/issues/62
 pub struct NamedTempFile<F = File> {
@@ -1017,7 +1012,7 @@ pub(crate) fn create_named(
     // Make the path absolute. Otherwise, changing directories could cause us to
     // delete the wrong file.
     if !path.is_absolute() {
-        path = env::current_dir()?.join(path)
+        path = std::env::current_dir()?.join(path)
     }
     imp::create_named(&path, open_options, permissions)
         .with_err_path(|| path.clone())

src/lib.rs

@@ -40,7 +40,7 @@
 //! use tempfile::tempdir;
 //! use std::process::Command;
 //!
-//! // Create a directory inside of `std::env::temp_dir()`.
+//! // Create a directory inside of `env::temp_dir()`.
 //! let temp_dir = tempdir()?;
 //!
 //! // Spawn the `touch` command inside the temporary directory and collect the exit status
@@ -67,7 +67,7 @@
 //! use tempfile::tempfile;
 //! use std::io::Write;
 //!
-//! // Create a file inside of `std::env::temp_dir()`.
+//! // Create a file inside of `env::temp_dir()`.
 //! let mut file = tempfile()?;
 //!
 //! writeln!(file, "Brian was here. Briefly.")?;
@@ -82,7 +82,7 @@
 //!
 //! let text = "Brian was here. Briefly.";
 //!
-//! // Create a file inside of `std::env::temp_dir()`.
+//! // Create a file inside of `env::temp_dir()`.
 //! let mut file1 = NamedTempFile::new()?;
 //!
 //! // Re-open it.
@@ -105,7 +105,7 @@
 //! use std::fs::File;
 //! use std::io::Write;
 //!
-//! // Create a directory inside of `std::env::temp_dir()`.
+//! // Create a directory inside of `env::temp_dir()`.
 //! let dir = tempdir()?;
 //!
 //! let file_path = dir.path().join("my-temporary-note.txt");
@@ -126,7 +126,6 @@
 //! [`tempdir()`]: fn.tempdir.html
 //! [`TempDir`]: struct.TempDir.html
 //! [`NamedTempFile`]: struct.NamedTempFile.html
-//! [`std::env::temp_dir()`]: https://doc.rust-lang.org/std/env/fn.temp_dir.html
 //! [`lazy_static`]: https://github.com/rust-lang-nursery/lazy-static.rs/issues/62
 
 #![doc(
@@ -147,15 +146,17 @@ const NUM_RAND_CHARS: usize = 6;
 
 use std::ffi::OsStr;
 use std::fs::OpenOptions;
+use std::io;
 use std::path::Path;
-use std::{env, io};
 
 mod dir;
 mod error;
 mod file;
 mod spooled;
 mod util;
 
+pub mod env;
+
 pub use crate::dir::{tempdir, tempdir_in, TempDir};
 pub use crate::file::{
     tempfile, tempfile_in, NamedTempFile, PathPersistError, PersistError, TempPath,
@@ -469,7 +470,7 @@ impl<'a, 'b> Builder<'a, 'b> {
         )
     }
 
-    /// Attempts to make a temporary directory inside of `env::temp_dir()` whose
+    /// Attempts to make a temporary directory inside of [`env::temp_dir()`] whose
     /// name will have the prefix, `prefix`. The directory and
     /// everything inside it will be automatically deleted once the
     /// returned `TempDir` is destroyed.
@@ -522,7 +523,7 @@ impl<'a, 'b> Builder<'a, 'b> {
         let storage;
         let mut dir = dir.as_ref();
         if !dir.is_absolute() {
-            let cur_dir = env::current_dir()?;
+            let cur_dir = std::env::current_dir()?;
             storage = cur_dir.join(dir);
             dir = &storage;
         }
@@ -540,7 +541,7 @@ impl<'a, 'b> Builder<'a, 'b> {
     /// Attempts to create a temporary file (or file-like object) using the
     /// provided closure. The closure is passed a temporary file path and
     /// returns an [`std::io::Result`]. The path provided to the closure will be
-    /// inside of [`std::env::temp_dir()`]. Use [`Builder::make_in`] to provide
+    /// inside of [`env::temp_dir()`]. Use [`Builder::make_in`] to provide
     /// a custom temporary directory. If the closure returns one of the
     /// following errors, then another randomized file path is tried:
     ///  - [`std::io::ErrorKind::AlreadyExists`]

tests/namedtempfile.rs

@@ -1,11 +1,10 @@
 #![deny(rust_2018_idioms)]
 
-use std::env;
 use std::ffi::{OsStr, OsString};
 use std::fs::File;
 use std::io::{Read, Seek, SeekFrom, Write};
 use std::path::{Path, PathBuf};
-use tempfile::{tempdir, Builder, NamedTempFile, TempPath};
+use tempfile::{env, tempdir, Builder, NamedTempFile, TempPath};
 
 fn exists<P: AsRef<Path>>(path: P) -> bool {
     std::fs::metadata(path.as_ref()).is_ok()
@@ -276,10 +275,10 @@ fn test_write_after_close() {
 
 #[test]
 fn test_change_dir() {
-    env::set_current_dir(env::temp_dir()).unwrap();
+    std::env::set_current_dir(env::temp_dir()).unwrap();
     let tmpfile = NamedTempFile::new_in(".").unwrap();
-    let path = env::current_dir().unwrap().join(tmpfile.path());
-    env::set_current_dir("/").unwrap();
+    let path = std::env::current_dir().unwrap().join(tmpfile.path());
+    std::env::set_current_dir("/").unwrap();
     drop(tmpfile);
     assert!(!exists(path))
 }

tests/tempdir.rs

@@ -10,7 +10,6 @@
 
 #![deny(rust_2018_idioms)]
 
-use std::env;
 use std::fs;
 use std::path::Path;
 use std::sync::mpsc::channel;
@@ -149,7 +148,7 @@ where
     F: FnOnce(),
 {
     let tmpdir = TempDir::new().unwrap();
-    assert!(env::set_current_dir(tmpdir.path()).is_ok());
+    assert!(std::env::set_current_dir(tmpdir.path()).is_ok());
 
     f();
 }