date: show error when reading dirs for -f arg (#4572)

Co-authored-by: Sylvestre Ledru <sylvestre@debian.org>

src/uu/date/src/date.rs

@@ -19,7 +19,7 @@ use std::fs::File;
 use std::io::{BufRead, BufReader};
 use std::path::PathBuf;
 use uucore::display::Quotable;
-#[cfg(not(any(target_os = "macos", target_os = "redox")))]
+#[cfg(not(any(target_os = "redox")))]
 use uucore::error::FromIo;
 use uucore::error::{UResult, USimpleError};
 use uucore::{format_usage, help_about, help_usage, show};
@@ -219,19 +219,19 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
                 let iter = std::iter::once(date);
                 Box::new(iter)
             }
-            DateSource::File(ref path) => match File::open(path) {
+            DateSource::File(ref path) => {
-                Ok(file) => {
+                if path.is_dir() {
-                    let lines = BufReader::new(file).lines();
-                    let iter = lines.filter_map(Result::ok).map(parse_date);
-                    Box::new(iter)
-                }
-                Err(_err) => {
                     return Err(USimpleError::new(
                         2,
-                        format!("{}: No such file or directory", path.display()),
+                        format!("expected file, got directory {}", path.quote()),
                     ));
                 }
-            },
+                let file = File::open(path)
+                    .map_err_context(|| path.as_os_str().to_string_lossy().to_string())?;
+                let lines = BufReader::new(file).lines();
+                let iter = lines.map_while(Result::ok).map(parse_date);
+                Box::new(iter)
+            }
             DateSource::Now => {
                 let iter = std::iter::once(Ok(now));
                 Box::new(iter)

tests/by-util/test_date.rs

@@ -283,6 +283,16 @@ fn test_date_for_invalid_file() {
     );
 }
 
+#[test]
+fn test_date_for_dir_as_file() {
+    let result = new_ucmd!().arg("--file").arg("/").fails();
+    result.no_stdout();
+    assert_eq!(
+        result.stderr_str().trim(),
+        "date: expected file, got directory '/'",
+    );
+}
+
 #[test]
 fn test_date_for_file() {
     let (at, mut ucmd) = at_and_ucmd!();