feat: add /dev/null handling

brush-core/src/shell/fs.rs

@@ -185,6 +185,14 @@ impl<SE: crate::extensions::ShellExtensions> crate::Shell<SE> {
         path: impl AsRef<Path>,
         params: &ExecutionParameters,
     ) -> Result<openfiles::OpenFile, std::io::Error> {
+        // Give platform-specific code a chance to handle special files
+        // (e.g. /dev/null on Windows, which needs to open NUL instead).
+        // This is checked before absolute_path so that paths like /dev/null
+        // are intercepted on platforms where they aren't valid native paths.
+        if let Some(result) = crate::sys::fs::try_open_special_file(path.as_ref()) {
+            return result.map(openfiles::OpenFile::from);
+        }
+
         let path_to_open = self.absolute_path(path.as_ref());
 
         // See if this is a reference to a file descriptor, in which case the actual

brush-core/src/sys/stubs/fs.rs

@@ -76,3 +76,12 @@ pub fn get_default_standard_utils_paths() -> Vec<std::path::PathBuf> {
 pub fn open_null_file() -> Result<std::fs::File, error::Error> {
     Err(error::ErrorKind::NotSupportedOnThisPlatform("opening null file").into())
 }
+
+/// Gives the platform an opportunity to handle a special file path (e.g. `/dev/null`).
+//
+// This is a stub implementation that returns no result.
+pub fn try_open_special_file(
+    _path: &std::path::Path,
+) -> Option<Result<std::fs::File, std::io::Error>> {
+    None
+}

brush-core/src/sys/unix/fs.rs

@@ -191,3 +191,8 @@ pub fn open_null_file() -> Result<std::fs::File, error::Error> {
 
     Ok(f)
 }
+
+/// Gives the platform an opportunity to handle a special file path (e.g. `/dev/null`).
+pub const fn try_open_special_file(_path: &Path) -> Option<Result<std::fs::File, std::io::Error>> {
+    None
+}

brush-core/src/sys/windows/fs.rs

@@ -2,9 +2,31 @@
 
 pub use crate::sys::stubs::fs::*;
 
+use std::path::Path;
+
+use crate::error;
+
 /// Splits a platform-specific PATH-like value into individual paths.
 ///
 /// On Windows, this delegates to [`std::env::split_paths`].
 pub fn split_paths<T: AsRef<std::ffi::OsStr> + ?Sized>(s: &T) -> std::env::SplitPaths<'_> {
     std::env::split_paths(s)
 }
+
+/// Opens a null file that will discard all I/O.
+pub fn open_null_file() -> Result<std::fs::File, error::Error> {
+    let f = std::fs::File::options()
+        .read(true)
+        .write(true)
+        .open("NUL")?;
+    Ok(f)
+}
+
+/// Gives the platform an opportunity to handle a special file path (e.g. `/dev/null`).
+pub fn try_open_special_file(path: &Path) -> Option<Result<std::fs::File, std::io::Error>> {
+    if path == Path::new("/dev/null") {
+        Some(open_null_file().map_err(std::io::Error::other))
+    } else {
+        None
+    }
+}

brush-shell/tests/cases/compat/redirection.yaml

@@ -107,6 +107,32 @@ cases:
       echo "Done."
       echo "${var}"
 
+  - name: "Input redirection from /dev/null"
+    stdin: |
+      cat < /dev/null
+      echo "exit: $?"
+
+  - name: "Redirect stderr to /dev/null"
+    stdin: |
+      ls /non-existent-path 2>/dev/null
+      echo "exit: $?"
+
+  - name: "Append redirection to /dev/null"
+    stdin: |
+      echo hi >>/dev/null
+      echo "exit: $?"
+
+  - name: "Redirect to /dev/null via variable"
+    stdin: |
+      target=/dev/null
+      echo hi >"$target"
+      echo "exit: $?"
+
+  - name: "Read and write /dev/null"
+    stdin: |
+      cat <>/dev/null
+      echo "exit: $?"
+
   - name: "Redirect stdout and stderr"
     stdin: |
       ls -d . non-existent-dir &>/dev/null