feat: implement cd - (#201)

brush-core/src/builtins/cd.rs

@@ -5,7 +5,7 @@ use clap::Parser;
 
 use crate::{builtins, commands};
 
-/// Change the current working directory.
+/// Change the current shell working directory.
 #[derive(Parser)]
 pub(crate) struct CdCommand {
     /// Force following symlinks.
@@ -16,7 +16,7 @@ pub(crate) struct CdCommand {
     #[arg(short = 'P')]
     use_physical_dir: bool,
 
-    /// Exit if current working dir resolution fails.
+    /// Exit with non zero exit status if current working directory resolution fails.
     #[arg(short = 'e')]
     exit_on_failed_cwd_resolution: bool,
 
@@ -25,6 +25,8 @@ pub(crate) struct CdCommand {
     #[arg(short = '@')]
     file_with_xattr_as_dir: bool,
 
+    /// By default it is the value of the HOME shell variable. If `TARGET_DIR` is "-", it is
+    /// converted to $OLDPWD.
     target_dir: Option<PathBuf>,
 }
 
@@ -43,8 +45,22 @@ impl builtins::Command for CdCommand {
             return crate::error::unimp("options to cd");
         }
 
+        let mut should_print = false;
         let target_dir = if let Some(target_dir) = &self.target_dir {
-            target_dir.clone()
+            // `cd -', equivalent to `cd $OLDPWD'
+            if target_dir.as_os_str() == "-" {
+                should_print = true;
+                if let Some(oldpwd) = context.shell.env.get_str("OLDPWD") {
+                    PathBuf::from(oldpwd.to_string())
+                } else {
+                    writeln!(context.stderr(), "OLDPWD not set")?;
+                    return Ok(builtins::ExitCode::Custom(1));
+                }
+            } else {
+                // TODO: remove clone, and use temporary lifetime extension after rust 1.75
+                target_dir.clone()
+            }
+        // `cd' without arguments is equivalent to `cd $HOME'
         } else {
             if let Some(home_var) = context.shell.env.get_str("HOME") {
                 PathBuf::from(home_var.to_string())
@@ -54,12 +70,18 @@ impl builtins::Command for CdCommand {
             }
         };
 
-        match context.shell.set_working_dir(&target_dir) {
-            Ok(()) => {}
-            Err(e) => {
-                writeln!(context.stderr(), "cd: {e}")?;
-                return Ok(builtins::ExitCode::Custom(1));
-            }
+        if let Err(e) = context.shell.set_working_dir(&target_dir) {
+            writeln!(context.stderr(), "cd: {e}")?;
+            return Ok(builtins::ExitCode::Custom(1));
+        }
+
+        // Bash compatibility
+        // https://www.gnu.org/software/bash/manual/bash.html#index-cd
+        // If a non-empty directory name from CDPATH is used, or if '-' is the first argument, and
+        // the directory change is successful, the absolute pathname of the new working
+        // directory is written to the standard output.
+        if should_print {
+            writeln!(context.stdout(), "{}", target_dir.display())?;
         }
 
         Ok(builtins::ExitCode::Success)

brush-core/src/shell.rs

@@ -969,8 +969,6 @@ impl Shell {
 
         let pwd = cleaned_path.to_string_lossy().to_string();
 
-        // TODO: handle updating PWD
-        self.working_dir = cleaned_path;
         self.env.update_or_add(
             "PWD",
             variables::ShellValueLiteral::Scalar(pwd),
@@ -981,6 +979,18 @@ impl Shell {
             EnvironmentLookup::Anywhere,
             EnvironmentScope::Global,
         )?;
+        let oldpwd = std::mem::replace(&mut self.working_dir, cleaned_path);
+
+        self.env.update_or_add(
+            "OLDPWD",
+            variables::ShellValueLiteral::Scalar(oldpwd.to_string_lossy().to_string()),
+            |var| {
+                var.export();
+                Ok(())
+            },
+            EnvironmentLookup::Anywhere,
+            EnvironmentScope::Global,
+        )?;
 
         Ok(())
     }

brush-shell/tests/cases/builtins/cd.yaml

@@ -28,3 +28,16 @@ cases:
       cd file
       echo $?
       ls -1
+
+  - name: "cd -"
+    ignore_stderr: true
+    stdin: |
+      cd /
+      echo "pwd: $PWD"
+      cd usr
+      echo "pwd: $PWD"
+      echo "oldpwd: $OLDPWD"
+      cd -
+      echo $?
+      echo "pwd: $PWD"
+