Merge #73

73: Emit more informative error message when cwd does not exist r=matklad a=smoelius

Fixes #72 in the manner described in #72 (comment).

Nits are welcome.

Co-authored-by: Samuel Moelius <sam@moeli.us>

src/error.rs

@@ -12,7 +12,7 @@ pub struct Error {
 
 /// Note: this is intentionally not public.
 enum ErrorKind {
-    CurrentDir { err: io::Error },
+    CurrentDir { err: io::Error, path: Option<PathBuf> },
     Var { err: env::VarError, var: OsString },
     ReadFile { err: io::Error, path: PathBuf },
     ReadDir { err: io::Error, path: PathBuf },
@@ -37,7 +37,11 @@ impl From<ErrorKind> for Error {
 impl fmt::Display for Error {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match &*self.kind {
-            ErrorKind::CurrentDir { err } => write!(f, "failed to get current directory: {err}"),
+            ErrorKind::CurrentDir { err, path } => {
+                let suffix =
+                    path.as_ref().map_or(String::new(), |path| format!(" `{}`", path.display()));
+                write!(f, "failed to get current directory{suffix}: {err}")
+            }
             ErrorKind::Var { err, var } => {
                 let var = var.to_string_lossy();
                 write!(f, "failed to get environment variable `{var}`: {err}")
@@ -113,8 +117,8 @@ impl std::error::Error for Error {}
 
 /// `pub(crate)` constructors, visible only in this crate.
 impl Error {
-    pub(crate) fn new_current_dir(err: io::Error) -> Error {
-        ErrorKind::CurrentDir { err }.into()
+    pub(crate) fn new_current_dir(err: io::Error, path: Option<PathBuf>) -> Error {
+        ErrorKind::CurrentDir { err, path }.into()
     }
 
     pub(crate) fn new_var(err: env::VarError, var: OsString) -> Error {

src/lib.rs

@@ -391,7 +391,7 @@ impl Shell {
     ///
     /// Fails if [`std::env::current_dir`] returns an error.
     pub fn new() -> Result<Shell> {
-        let cwd = current_dir().map_err(Error::new_current_dir)?;
+        let cwd = current_dir().map_err(|err| Error::new_current_dir(err, None))?;
         let cwd = RefCell::new(cwd);
         let env = RefCell::new(HashMap::new());
         Ok(Shell { cwd, env })
@@ -1013,7 +1013,18 @@ impl<'a> Cmd<'a> {
                 None => Stdio::null(),
             });
 
-            command.spawn().map_err(|err| Error::new_cmd_io(self, err))?
+            command.spawn().map_err(|err| {
+                // Try to determine whether the command failed because the current
+                // directory does not exist. Return an appropriate error in such a
+                // case.
+                if matches!(err.kind(), io::ErrorKind::NotFound) {
+                    let cwd = self.shell.cwd.borrow();
+                    if let Err(err) = cwd.metadata() {
+                        return Error::new_current_dir(err, Some(cwd.clone()));
+                    }
+                }
+                Error::new_cmd_io(self, err)
+            })?
         };
 
         let mut io_thread = None;

tests/it/main.rs

@@ -460,3 +460,19 @@ fn string_escapes() {
     assert_eq!(cmd!(sh, "\"\"\"asdf\"\"\"").to_string(), r##""""asdf""""##);
     assert_eq!(cmd!(sh, "\\\\").to_string(), r#"\\"#);
 }
+
+#[test]
+fn nonexistent_current_directory() {
+    let sh = setup();
+    sh.change_dir("nonexistent");
+    let err = cmd!(sh, "ls").run().unwrap_err();
+    if cfg!(unix) {
+        assert!(err.to_string().starts_with("failed to get current directory"));
+        assert!(err.to_string().ends_with("No such file or directory (os error 2)"));
+    } else {
+        assert_eq!(
+            err.to_string(),
+            "io error when running command `ls`: The directory name is invalid. (os error 267)"
+        );
+    }
+}