From 7ae9e0a7eb65146f90cb90403af0914b110f60cd Mon Sep 17 00:00:00 2001
From: Terts Diepraam <terts.diepraam@gmail.com>
Date: Sun, 26 Dec 2021 21:46:57 +0100
Subject: [PATCH] cksum: accept directories as empty files

---
 src/uu/cksum/src/cksum.rs   | 12 +++++++++---
 tests/by-util/test_cksum.rs |  5 ++---
 2 files changed, 11 insertions(+), 6 deletions(-)

diff --git a/src/uu/cksum/src/cksum.rs b/src/uu/cksum/src/cksum.rs
index a2d5112ec..ca87da2a8 100644
--- a/src/uu/cksum/src/cksum.rs
+++ b/src/uu/cksum/src/cksum.rs
@@ -80,12 +80,18 @@ fn cksum(fname: &str) -> io::Result<(u32, usize)> {
     let mut crc = 0u32;
     let mut size = 0usize;
 
-    let file;
     let mut rd: Box<dyn Read> = match fname {
         "-" => Box::new(stdin()),
         _ => {
-            file = File::open(Path::new(fname))?;
-            Box::new(BufReader::new(file))
+            let p = Path::new(fname);
+
+            // Directories should not give an error, but should be interpreted
+            // as empty files to match GNU semantics.
+            if p.is_dir() {
+                Box::new(BufReader::new(io::empty())) as Box<dyn Read>
+            } else {
+                Box::new(BufReader::new(File::open(p)?)) as Box<dyn Read>
+            }
         }
     };
 
diff --git a/tests/by-util/test_cksum.rs b/tests/by-util/test_cksum.rs
index bf31ceb18..66bdba9e3 100644
--- a/tests/by-util/test_cksum.rs
+++ b/tests/by-util/test_cksum.rs
@@ -74,9 +74,8 @@ fn test_invalid_file() {
     at.mkdir(folder_name);
     ts.ucmd()
         .arg(folder_name)
-        .fails()
-        .no_stdout()
-        .stderr_contains("cksum: asdf: Is a directory");
+        .succeeds()
+        .stdout_only("4294967295 0 asdf\n");
 }
 
 // Make sure crc is correct for files larger than 32 bytes