From 722936021747ec25df26f32e1aa17e3fe07c33b2 Mon Sep 17 00:00:00 2001
From: Michael Debertol <michael.debertol@gmail.com>
Date: Sat, 7 Aug 2021 21:31:05 +0200
Subject: [PATCH] cat: remove all per-file state

cat cannot keep per-file state, so move all remaining state (one_blank_kept)
to the global state.
---
 src/uu/cat/src/cat.rs     | 11 +++++++----
 tests/by-util/test_cat.rs | 12 ++++++++++++
 2 files changed, 19 insertions(+), 4 deletions(-)

diff --git a/src/uu/cat/src/cat.rs b/src/uu/cat/src/cat.rs
index 6b6f68b13..c71f60a7e 100644
--- a/src/uu/cat/src/cat.rs
+++ b/src/uu/cat/src/cat.rs
@@ -126,6 +126,9 @@ struct OutputState {
 
     /// Whether we skipped a \r, which still needs to be printed
     skipped_carriage_return: bool,
+
+    /// Whether we have already printed a blank line
+    one_blank_kept: bool,
 }
 
 /// Represents an open file handle, stream, or other device
@@ -343,6 +346,7 @@ fn cat_files(files: Vec<String>, options: &OutputOptions) -> UResult<()> {
         line_number: 1,
         at_line_start: true,
         skipped_carriage_return: false,
+        one_blank_kept: false,
     };
     let mut error_messages: Vec<String> = Vec::new();
 
@@ -431,7 +435,6 @@ fn write_lines<R: Read>(
     let mut in_buf = [0; 1024 * 31];
     let stdout = io::stdout();
     let mut writer = stdout.lock();
-    let mut one_blank_kept = false;
 
     while let Ok(n) = handle.reader.read(&mut in_buf) {
         if n == 0 {
@@ -447,8 +450,8 @@ fn write_lines<R: Read>(
                     writer.write_all(b"^M")?;
                     state.skipped_carriage_return = false;
                 }
-                if !state.at_line_start || !options.squeeze_blank || !one_blank_kept {
-                    one_blank_kept = true;
+                if !state.at_line_start || !options.squeeze_blank || !state.one_blank_kept {
+                    state.one_blank_kept = true;
                     if state.at_line_start && options.number == NumberingMode::All {
                         write!(&mut writer, "{0:6}\t", state.line_number)?;
                         state.line_number += 1;
@@ -467,7 +470,7 @@ fn write_lines<R: Read>(
                 state.skipped_carriage_return = false;
                 state.at_line_start = false;
             }
-            one_blank_kept = false;
+            state.one_blank_kept = false;
             if state.at_line_start && options.number != NumberingMode::None {
                 write!(&mut writer, "{0:6}\t", state.line_number)?;
                 state.line_number += 1;
diff --git a/tests/by-util/test_cat.rs b/tests/by-util/test_cat.rs
index eb50d7dce..e0bc49339 100644
--- a/tests/by-util/test_cat.rs
+++ b/tests/by-util/test_cat.rs
@@ -273,6 +273,18 @@ fn test_stdin_show_ends() {
             .stdout_only("\t\0$\n\t");
     }
 }
+
+#[test]
+fn squeeze_all_files() {
+    // empty lines at the end of a file are "squeezed" together with empty lines at the beginning
+    let (at, mut ucmd) = at_and_ucmd!();
+    at.write("input1", "a\n\n");
+    at.write("input2", "\n\nb");
+    ucmd.args(&["input1", "input2", "-s"])
+        .succeeds()
+        .stdout_only("a\n\nb");
+}
+
 #[test]
 fn test_show_ends_crlf() {
     new_ucmd!()