From 66359a0f564561edcba6ce154c7536a1cba7869e Mon Sep 17 00:00:00 2001
From: Michael Debertol <michael.debertol@gmail.com>
Date: Sun, 6 Jun 2021 11:31:42 +0200
Subject: [PATCH] sort: insert line separators after non-empty files

If files don't end witht a line separator we have to insert one,
otherwise the last line will be combined with the first line of the next
file.
---
 src/uu/sort/src/chunks.rs                    | 20 +++++++++++++++++---
 tests/by-util/test_sort.rs                   |  8 ++++++++
 tests/fixtures/sort/no_trailing_newline1.txt |  2 ++
 tests/fixtures/sort/no_trailing_newline2.txt |  1 +
 4 files changed, 28 insertions(+), 3 deletions(-)
 create mode 100644 tests/fixtures/sort/no_trailing_newline1.txt
 create mode 100644 tests/fixtures/sort/no_trailing_newline2.txt

diff --git a/src/uu/sort/src/chunks.rs b/src/uu/sort/src/chunks.rs
index 23567833b..3705f2cf7 100644
--- a/src/uu/sort/src/chunks.rs
+++ b/src/uu/sort/src/chunks.rs
@@ -175,6 +175,7 @@ fn read_to_buffer(
     separator: u8,
 ) -> (usize, bool) {
     let mut read_target = &mut buffer[start_offset..];
+    let mut last_file_target_size = read_target.len();
     loop {
         match file.read(read_target) {
             Ok(0) => {
@@ -208,14 +209,27 @@ fn read_to_buffer(
                         read_target = &mut buffer[len..];
                     }
                 } else {
-                    // This file is empty.
+                    // This file has been fully read.
+                    let mut leftover_len = read_target.len();
+                    if last_file_target_size != leftover_len {
+                        // The file was not empty.
+                        let read_len = buffer.len() - leftover_len;
+                        if buffer[read_len - 1] != separator {
+                            // The file did not end with a separator. We have to insert one.
+                            buffer[read_len] = separator;
+                            leftover_len -= 1;
+                        }
+                        let read_len = buffer.len() - leftover_len;
+                        read_target = &mut buffer[read_len..];
+                    }
                     if let Some(next_file) = next_files.next() {
                         // There is another file.
+                        last_file_target_size = leftover_len;
                         *file = next_file;
                     } else {
                         // This was the last file.
-                        let leftover_len = read_target.len();
-                        return (buffer.len() - leftover_len, false);
+                        let read_len = buffer.len() - leftover_len;
+                        return (read_len, false);
                     }
                 }
             }
diff --git a/tests/by-util/test_sort.rs b/tests/by-util/test_sort.rs
index 02636b027..97127b995 100644
--- a/tests/by-util/test_sort.rs
+++ b/tests/by-util/test_sort.rs
@@ -792,3 +792,11 @@ fn test_nonexistent_file() {
 fn test_blanks() {
     test_helper("blanks", &["-b", "--ignore-blanks"]);
 }
+
+#[test]
+fn sort_multiple() {
+    new_ucmd!()
+        .args(&["no_trailing_newline1.txt", "no_trailing_newline2.txt"])
+        .succeeds()
+        .stdout_is("a\nb\nb\n");
+}
diff --git a/tests/fixtures/sort/no_trailing_newline1.txt b/tests/fixtures/sort/no_trailing_newline1.txt
new file mode 100644
index 000000000..0a207c060
--- /dev/null
+++ b/tests/fixtures/sort/no_trailing_newline1.txt
@@ -0,0 +1,2 @@
+a
+b
\ No newline at end of file
diff --git a/tests/fixtures/sort/no_trailing_newline2.txt b/tests/fixtures/sort/no_trailing_newline2.txt
new file mode 100644
index 000000000..63d8dbd40
--- /dev/null
+++ b/tests/fixtures/sort/no_trailing_newline2.txt
@@ -0,0 +1 @@
+b
\ No newline at end of file