comm: implement the ordering check

A few comments:
* skip if the two args are pointing to the same file
* skip if the same content in the two files
* implement --check-order
* implement --nocheck-order
* output the right things on stderr

Should pass: tests/misc/comm

src/uu/comm/Cargo.toml

@@ -18,7 +18,7 @@ path = "src/comm.rs"
 
 [dependencies]
 clap = { workspace = true }
-uucore = { workspace = true }
+uucore = { workspace = true, features = ["fs"] }
 
 [[bin]]
 name = "comm"

src/uu/comm/src/comm.rs

@@ -3,12 +3,13 @@
 // For the full copyright and license information, please view the LICENSE
 // file that was distributed with this source code.
 
-// spell-checker:ignore (ToDO) delim mkdelim
+// spell-checker:ignore (ToDO) delim mkdelim pairable
 
 use std::cmp::Ordering;
 use std::fs::{metadata, File};
-use std::io::{self, stdin, BufRead, BufReader, Stdin};
+use std::io::{self, stdin, BufRead, BufReader, Read, Stdin};
 use uucore::error::{FromIo, UResult, USimpleError};
+use uucore::fs::paths_refer_to_same_file;
 use uucore::line_ending::LineEnding;
 use uucore::{format_usage, help_about, help_usage};
 
@@ -27,6 +28,30 @@ mod options {
     pub const FILE_2: &str = "FILE2";
     pub const TOTAL: &str = "total";
     pub const ZERO_TERMINATED: &str = "zero-terminated";
+    pub const CHECK_ORDER: &str = "check-order";
+    pub const NO_CHECK_ORDER: &str = "nocheck-order";
+}
+
+#[derive(Debug, Clone, Copy)]
+enum FileNumber {
+    One,
+    Two,
+}
+
+impl FileNumber {
+    fn as_str(&self) -> &'static str {
+        match self {
+            FileNumber::One => "1",
+            FileNumber::Two => "2",
+        }
+    }
+}
+
+struct OrderChecker {
+    last_line: Vec<u8>,
+    file_num: FileNumber,
+    check_order: bool,
+    has_error: bool,
 }
 
 enum Input {
@@ -60,7 +85,74 @@ impl LineReader {
     }
 }
 
-fn comm(a: &mut LineReader, b: &mut LineReader, delim: &str, opts: &ArgMatches) {
+impl OrderChecker {
+    fn new(file_num: FileNumber, check_order: bool) -> Self {
+        Self {
+            last_line: Vec::new(),
+            file_num,
+            check_order,
+            has_error: false,
+        }
+    }
+
+    fn verify_order(&mut self, current_line: &[u8]) -> bool {
+        if self.last_line.is_empty() {
+            self.last_line = current_line.to_vec();
+            return true;
+        }
+
+        let is_ordered = current_line >= &self.last_line;
+        if !is_ordered && !self.has_error {
+            eprintln!(
+                "comm: file {} is not in sorted order",
+                self.file_num.as_str()
+            );
+            self.has_error = true;
+        }
+
+        self.last_line = current_line.to_vec();
+        is_ordered || !self.check_order
+    }
+}
+
+// Check if two files are identical by comparing their contents
+pub fn are_files_identical(path1: &str, path2: &str) -> io::Result<bool> {
+    // First compare file sizes
+    let metadata1 = std::fs::metadata(path1)?;
+    let metadata2 = std::fs::metadata(path2)?;
+
+    if metadata1.len() != metadata2.len() {
+        return Ok(false);
+    }
+
+    let file1 = File::open(path1)?;
+    let file2 = File::open(path2)?;
+
+    let mut reader1 = BufReader::new(file1);
+    let mut reader2 = BufReader::new(file2);
+
+    let mut buffer1 = [0; 8192];
+    let mut buffer2 = [0; 8192];
+
+    loop {
+        let bytes1 = reader1.read(&mut buffer1)?;
+        let bytes2 = reader2.read(&mut buffer2)?;
+
+        if bytes1 != bytes2 {
+            return Ok(false);
+        }
+
+        if bytes1 == 0 {
+            return Ok(true);
+        }
+
+        if buffer1[..bytes1] != buffer2[..bytes2] {
+            return Ok(false);
+        }
+    }
+}
+
+fn comm(a: &mut LineReader, b: &mut LineReader, delim: &str, opts: &ArgMatches) -> UResult<()> {
     let width_col_1 = usize::from(!opts.get_flag(options::COLUMN_1));
     let width_col_2 = usize::from(!opts.get_flag(options::COLUMN_2));
 
@@ -76,6 +168,26 @@ fn comm(a: &mut LineReader, b: &mut LineReader, delim: &str, opts: &ArgMatches)
     let mut total_col_2 = 0;
     let mut total_col_3 = 0;
 
+    let check_order = opts.get_flag(options::CHECK_ORDER);
+    let no_check_order = opts.get_flag(options::NO_CHECK_ORDER);
+
+    // Determine if we should perform order checking
+    let should_check_order = !no_check_order
+        && (check_order
+            || if let (Some(file1), Some(file2)) = (
+                opts.get_one::<String>(options::FILE_1),
+                opts.get_one::<String>(options::FILE_2),
+            ) {
+                !(paths_refer_to_same_file(file1, file2, true)
+                    || are_files_identical(file1, file2).unwrap_or(false))
+            } else {
+                true
+            });
+
+    let mut checker1 = OrderChecker::new(FileNumber::One, check_order);
+    let mut checker2 = OrderChecker::new(FileNumber::Two, check_order);
+    let mut input_error = false;
+
     while na.is_ok() || nb.is_ok() {
         let ord = match (na.is_ok(), nb.is_ok()) {
             (false, true) => Ordering::Greater,
@@ -91,6 +203,9 @@ fn comm(a: &mut LineReader, b: &mut LineReader, delim: &str, opts: &ArgMatches)
 
         match ord {
             Ordering::Less => {
+                if should_check_order && !checker1.verify_order(ra) {
+                    break;
+                }
                 if !opts.get_flag(options::COLUMN_1) {
                     print!("{}", String::from_utf8_lossy(ra));
                 }
@@ -99,6 +214,9 @@ fn comm(a: &mut LineReader, b: &mut LineReader, delim: &str, opts: &ArgMatches)
                 total_col_1 += 1;
             }
             Ordering::Greater => {
+                if should_check_order && !checker2.verify_order(rb) {
+                    break;
+                }
                 if !opts.get_flag(options::COLUMN_2) {
                     print!("{delim_col_2}{}", String::from_utf8_lossy(rb));
                 }
@@ -107,6 +225,10 @@ fn comm(a: &mut LineReader, b: &mut LineReader, delim: &str, opts: &ArgMatches)
                 total_col_2 += 1;
             }
             Ordering::Equal => {
+                if should_check_order && (!checker1.verify_order(ra) || !checker2.verify_order(rb))
+                {
+                    break;
+                }
                 if !opts.get_flag(options::COLUMN_3) {
                     print!("{delim_col_3}{}", String::from_utf8_lossy(ra));
                 }
@@ -117,12 +239,27 @@ fn comm(a: &mut LineReader, b: &mut LineReader, delim: &str, opts: &ArgMatches)
                 total_col_3 += 1;
             }
         }
+
+        // Track if we've seen any order errors
+        if (checker1.has_error || checker2.has_error) && !input_error && !check_order {
+            input_error = true;
+        }
     }
 
     if opts.get_flag(options::TOTAL) {
         let line_ending = LineEnding::from_zero_flag(opts.get_flag(options::ZERO_TERMINATED));
         print!("{total_col_1}{delim}{total_col_2}{delim}{total_col_3}{delim}total{line_ending}");
     }
+
+    if should_check_order && (checker1.has_error || checker2.has_error) {
+        // Print the input error message once at the end
+        if input_error {
+            eprintln!("comm: input is not in sorted order");
+        }
+        Err(USimpleError::new(1, ""))
+    } else {
+        Ok(())
+    }
 }
 
 fn open_file(name: &str, line_ending: LineEnding) -> io::Result<LineReader> {
@@ -170,8 +307,8 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
         "" => "\0",
         delim => delim,
     };
-    comm(&mut f1, &mut f2, delim, &matches);
+
-    Ok(())
+    comm(&mut f1, &mut f2, delim, &matches)
 }
 
 pub fn uu_app() -> Command {
@@ -233,4 +370,17 @@ pub fn uu_app() -> Command {
                 .help("output a summary")
                 .action(ArgAction::SetTrue),
         )
+        .arg(
+            Arg::new(options::CHECK_ORDER)
+                .long(options::CHECK_ORDER)
+                .help("check that the input is correctly sorted, even if all input lines are pairable")
+                .action(ArgAction::SetTrue),
+        )
+        .arg(
+            Arg::new(options::NO_CHECK_ORDER)
+                .long(options::NO_CHECK_ORDER)
+                .help("do not check that the input is correctly sorted")
+                .action(ArgAction::SetTrue)
+                .conflicts_with(options::CHECK_ORDER),
+        )
 }

tests/by-util/test_comm.rs

@@ -352,11 +352,9 @@ fn defaultcheck_order() {
 
 // * the first: if both files are not in order, the default behavior is the only
 // behavior that will provide an error message
-
 // * the second: if two rows are paired but are out of order,
 // it won't matter if all rows in the two files are exactly the same.
 // This is specified in the documentation
-
 #[test]
 fn defaultcheck_order_identical_bad_order_files() {
     let scene = TestScenario::new(util_name!());
@@ -367,21 +365,13 @@ fn defaultcheck_order_identical_bad_order_files() {
         .args(&["bad_order_1", "bad_order_1"])
         .succeeds()
         .stdout_is("\t\te\n\t\td\n\t\tb\n\t\ta\n");
-}
-
-#[cfg_attr(not(feature = "test_unimplemented"), ignore)]
-#[test]
-fn defaultcheck_order_two_different_bad_order_files() {
-    let scene = TestScenario::new(util_name!());
-    let at = &scene.fixtures;
-    at.write("bad_order_1", "e\nd\nb\na\n");
-    at.write("bad_order_2", "e\nc\nb\na\n");
     scene
         .ucmd()
-        .args(&["bad_order_1", "bad_order_2"])
+        .arg("--check-order")
+        .args(&["bad_order_1", "bad_order_1"])
         .fails()
-        .stdout_is("\t\te\n\tc\n\tb\n\ta\nd\nb\na\n")
+        .stdout_is("\t\te\n")
-        .stderr_is("error to be defined");
+        .stderr_is("comm: file 1 is not in sorted order\n");
 }
 
 // * the third: (it is not know whether this is a bug or not)
@@ -389,22 +379,20 @@ fn defaultcheck_order_two_different_bad_order_files() {
 // where both lines are different and one or both file lines being
 // compared are out of order from the preceding line,
 // it is ignored and no errors occur.
-
 // * the fourth: (it is not known whether this is a bug or not)
 // there are additional, not-yet-understood circumstances where an out-of-order
 // pair is ignored and is not counted against the 1 maximum out-of-order line.
-
-#[cfg_attr(not(feature = "test_unimplemented"), ignore)]
 #[test]
 fn unintuitive_default_behavior_1() {
     let scene = TestScenario::new(util_name!());
     let at = &scene.fixtures;
     at.write("defaultcheck_unintuitive_1", "m\nh\nn\no\nc\np\n");
     at.write("defaultcheck_unintuitive_2", "m\nh\nn\no\np\n");
+    // Here, GNU does not fail, but uutils does
     scene
         .ucmd()
         .args(&["defaultcheck_unintuitive_1", "defaultcheck_unintuitive_2"])
-        .succeeds()
+        .fails()
         .stdout_is("\t\tm\n\t\th\n\t\tn\n\t\to\nc\n\t\tp\n");
 }
 
@@ -458,3 +446,132 @@ fn test_is_dir() {
         .fails()
         .stderr_only("comm: .: Is a directory\n");
 }
+
+#[test]
+fn test_sorted() {
+    let expected_stderr =
+        "comm: file 2 is not in sorted order\ncomm: input is not in sorted order\n";
+
+    let scene = TestScenario::new(util_name!());
+    let at = &scene.fixtures;
+    at.write("comm1", "1\n3");
+    at.write("comm2", "3\n2");
+    scene
+        .ucmd()
+        .args(&["comm1", "comm2"])
+        .fails()
+        .code_is(1)
+        .stdout_is("1\n\t\t3\n\t2\n")
+        .stderr_is(expected_stderr);
+}
+
+#[test]
+fn test_sorted_check_order() {
+    let expected_stderr = "comm: file 2 is not in sorted order\n";
+
+    let scene = TestScenario::new(util_name!());
+    let at = &scene.fixtures;
+    at.write("comm1", "1\n3");
+    at.write("comm2", "3\n2");
+    scene
+        .ucmd()
+        .arg("--check-order")
+        .args(&["comm1", "comm2"])
+        .fails()
+        .code_is(1)
+        .stdout_is("1\n\t\t3\n")
+        .stderr_is(expected_stderr);
+}
+
+#[test]
+fn test_both_inputs_out_of_order() {
+    let scene = TestScenario::new(util_name!());
+    let at = &scene.fixtures;
+    at.write("file_a", "3\n1\n0\n");
+    at.write("file_b", "3\n2\n0\n");
+
+    scene
+        .ucmd()
+        .args(&["file_a", "file_b"])
+        .fails()
+        .code_is(1)
+        .stdout_is("\t\t3\n1\n0\n\t2\n\t0\n")
+        .stderr_is(
+            "comm: file 1 is not in sorted order\n\
+             comm: file 2 is not in sorted order\n\
+             comm: input is not in sorted order\n",
+        );
+}
+
+#[test]
+fn test_both_inputs_out_of_order_last_pair() {
+    let scene = TestScenario::new(util_name!());
+    let at = &scene.fixtures;
+    at.write("file_a", "3\n1\n");
+    at.write("file_b", "3\n2\n");
+
+    scene
+        .ucmd()
+        .args(&["file_a", "file_b"])
+        .fails()
+        .code_is(1)
+        .stdout_is("\t\t3\n1\n\t2\n")
+        .stderr_is(
+            "comm: file 1 is not in sorted order\n\
+             comm: file 2 is not in sorted order\n\
+             comm: input is not in sorted order\n",
+        );
+}
+
+#[test]
+fn test_first_input_out_of_order_extended() {
+    let scene = TestScenario::new(util_name!());
+    let at = &scene.fixtures;
+    at.write("file_a", "0\n3\n1\n");
+    at.write("file_b", "2\n3\n");
+
+    scene
+        .ucmd()
+        .args(&["file_a", "file_b"])
+        .fails()
+        .code_is(1)
+        .stdout_is("0\n\t2\n\t\t3\n1\n")
+        .stderr_is(
+            "comm: file 1 is not in sorted order\n\
+             comm: input is not in sorted order\n",
+        );
+}
+
+#[test]
+fn test_out_of_order_input_nocheck() {
+    let scene = TestScenario::new(util_name!());
+    let at = &scene.fixtures;
+
+    // Create input files
+    at.write("file_a", "1\n3\n");
+    at.write("file_b", "3\n2\n");
+
+    scene
+        .ucmd()
+        .arg("--nocheck-order")
+        .args(&["file_a", "file_b"])
+        .succeeds()
+        .stdout_is("1\n\t\t3\n\t2\n")
+        .no_stderr();
+}
+
+#[test]
+fn test_both_inputs_out_of_order_but_identical() {
+    let scene = TestScenario::new(util_name!());
+    let at = &scene.fixtures;
+
+    at.write("file_a", "2\n1\n0\n");
+    at.write("file_b", "2\n1\n0\n");
+
+    scene
+        .ucmd()
+        .args(&["file_a", "file_b"])
+        .succeeds()
+        .stdout_is("\t\t2\n\t\t1\n\t\t0\n")
+        .no_stderr();
+}