sort: defer compress program errors until needed

src/uu/sort/src/ext_sort/threaded.rs

@@ -52,6 +52,8 @@ pub fn ext_sort(
 
     // Test if compression program exists and works, disable if not
     let mut effective_settings = settings.clone();
+    // Keep the error until we know compression is actually needed.
+    let mut compress_prog_error = None;
     if let Some(ref prog) = settings.compress_prog {
         // Test the compression program by trying to spawn it
         match std::process::Command::new(prog)
@@ -65,12 +67,7 @@ pub fn ext_sort(
                 let _ = child.kill();
             }
             Err(err) => {
-                // Print the error and disable compression
-                let _ = writeln!(
-                    stderr(),
-                    "sort: could not run compress program '{prog}': {}",
-                    strip_errno(&err)
-                );
+                compress_prog_error = Some((prog.clone(), err));
                 effective_settings.compress_prog = None;
             }
         }
@@ -80,6 +77,7 @@ pub fn ext_sort(
         reader_writer::<_, WriteableCompressedTmpFile>(
             files,
             &effective_settings,
+            None,
             &sorted_receiver,
             recycled_sender,
             output,
@@ -89,6 +87,7 @@ pub fn ext_sort(
         reader_writer::<_, WriteablePlainTmpFile>(
             files,
             &effective_settings,
+            compress_prog_error,
             &sorted_receiver,
             recycled_sender,
             output,
@@ -103,6 +102,7 @@ fn reader_writer<
 >(
     files: F,
     settings: &GlobalSettings,
+    compress_prog_error: Option<(String, std::io::Error)>,
     receiver: &Receiver<Chunk>,
     sender: SyncSender<Chunk>,
     output: Output,
@@ -125,6 +125,7 @@ fn reader_writer<
         separator,
         buffer_size,
         settings,
+        compress_prog_error,
         receiver,
         sender,
     )?;
@@ -207,12 +208,14 @@ enum ReadResult<I: WriteableTmpFile> {
     WroteChunksToFile { tmp_files: Vec<I::Closed> },
 }
 /// The function that is executed on the reader/writer thread.
+#[allow(clippy::too_many_arguments)]
 fn read_write_loop<I: WriteableTmpFile>(
     mut files: impl Iterator<Item = UResult<Box<dyn Read + Send>>>,
     tmp_dir: &mut TmpDirWrapper,
     separator: u8,
     buffer_size: usize,
     settings: &GlobalSettings,
+    compress_prog_error: Option<(String, std::io::Error)>,
     receiver: &Receiver<Chunk>,
     sender: SyncSender<Chunk>,
 ) -> UResult<ReadResult<I>> {
@@ -249,6 +252,15 @@ fn read_write_loop<I: WriteableTmpFile>(
         }
     }
 
+    // The input did not fit into the first two in-memory chunks.
+    if let Some((prog, err)) = compress_prog_error {
+        let _ = writeln!(
+            stderr(),
+            "sort: could not run compress program '{prog}': {}",
+            strip_errno(&err)
+        );
+    }
+
     let mut sender_option = Some(sender);
     let mut tmp_files = vec![];
     loop {

tests/by-util/test_sort.rs

@@ -1374,7 +1374,7 @@ fn test_compress_fail() {
             "--compress-program",
             "nonexistent-program",
             "-S",
-            "10",
+            "1K",
         ])
         .succeeds();
 
@@ -1394,6 +1394,20 @@ fn test_compress_fail() {
     assert_eq!(result.stdout_str(), expected);
 }
 
+#[test]
+#[cfg(unix)]
+fn test_input_error_before_compression_is_needed() {
+    let (at, mut ucmd) = at_and_ucmd!();
+    at.write("input", "b\na\n");
+    at.mkdir("directory");
+
+    ucmd.args(&["--compress-program=nonexistent", "input", "directory"])
+        .fails_with_code(2)
+        .no_stdout()
+        .stderr_contains("Is a directory")
+        .stderr_does_not_contain("compress program");
+}
+
 #[test]
 fn test_merge_batches() {
     new_ucmd!()