du: Flags 'm', 'k', 'm' should be POSIX style overriden (#10664)

* du: Flags 'm', 'k', 'm' should be POSIX style overriden

* du: overwriting b flag doesnt deactivate --apparent-size

src/uu/du/src/du.rs

@@ -963,6 +963,40 @@ fn read_files_from(file_name: &OsStr) -> Result<Vec<PathBuf>, std::io::Error> {
     Ok(paths)
 }
 
+fn get_block_size_arg_index_if_present(matches: &ArgMatches, flag: &str) -> Option<usize> {
+    if matches.get_flag(flag) {
+        // Indices of returns index even if flag is not present, thats why we need to if guard it
+        matches
+            .indices_of(flag)
+            .and_then(|mut indices| indices.next_back())
+    } else {
+        None
+    }
+}
+
+fn handle_block_size_arg_override(matches: &ArgMatches) -> Option<SizeFormat> {
+    let candidates = [
+        (
+            SizeFormat::BlockSize(1),
+            get_block_size_arg_index_if_present(matches, options::BYTES),
+        ),
+        (
+            SizeFormat::BlockSize(1024),
+            get_block_size_arg_index_if_present(matches, options::BLOCK_SIZE_1K),
+        ),
+        (
+            SizeFormat::BlockSize(1024 * 1024),
+            get_block_size_arg_index_if_present(matches, options::BLOCK_SIZE_1M),
+        ),
+    ];
+
+    candidates
+        .into_iter()
+        .filter(|(_, idx)| idx.is_some())
+        .max_by_key(|&(_, idx)| idx.unwrap_or(0))
+        .map(|(size_format, _)| size_format)
+}
+
 #[uucore::main]
 #[allow(clippy::cognitive_complexity)]
 pub fn uumain(args: impl uucore::Args) -> UResult<()> {
@@ -1018,12 +1052,8 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
         SizeFormat::HumanBinary
     } else if matches.get_flag(options::SI) {
         SizeFormat::HumanDecimal
-    } else if matches.get_flag(options::BYTES) {
-        SizeFormat::BlockSize(1)
-    } else if matches.get_flag(options::BLOCK_SIZE_1K) {
-        SizeFormat::BlockSize(1024)
-    } else if matches.get_flag(options::BLOCK_SIZE_1M) {
-        SizeFormat::BlockSize(1024 * 1024)
+    } else if let Some(size_format) = handle_block_size_arg_override(&matches) {
+        size_format
     } else {
         let block_size_str = matches.get_one::<String>(options::BLOCK_SIZE);
         let block_size = read_block_size(block_size_str.map(AsRef::as_ref))?;

tests/by-util/test_du.rs

@@ -2058,3 +2058,96 @@ fn test_du_symlinks_multiple_links_in_args() {
     result.stdout_contains("dir1/file");
     result.stdout_does_not_contain("dir1/link");
 }
+
+#[test]
+fn test_block_size_args_override() {
+    let ts = TestScenario::new(util_name!());
+    let at = &ts.fixtures;
+    let dir = "override_args_dir";
+
+    at.mkdir(dir);
+    let fpath = at.plus(format!("{dir}/file"));
+    std::fs::File::create(fpath)
+        .expect("cannot create test file")
+        .set_len(100_000_000)
+        .expect("cannot set file size");
+
+    let fpath2 = at.plus(format!("{dir}/file_2"));
+    std::fs::File::create(fpath2)
+        .expect("cannot create test file")
+        .set_len(100_000_000)
+        .expect("cannot set file size");
+
+    let test_cases = [
+        (["-sk", "-m"], "-sm"),
+        (["-sk", "-b"], "-sb"),
+        (["-sm", "-k"], "-sk"),
+    ];
+
+    for (idx, (overwriting_args, expected)) in test_cases.into_iter().enumerate() {
+        let overridden_args = ts
+            .ucmd()
+            .arg(dir)
+            .args(&overwriting_args)
+            .succeeds()
+            .stdout_move_str();
+
+        let single_args = ts
+            .ucmd()
+            .arg(dir)
+            .arg(expected)
+            .succeeds()
+            .stdout_move_str();
+
+        assert_eq!(
+            overridden_args, single_args,
+            "The last argument of m, k and b should overwrite. Run: {idx}"
+        );
+    }
+}
+
+#[test]
+fn test_block_override_b_still_has_apparent_size() {
+    let ts = TestScenario::new(util_name!());
+    let at = &ts.fixtures;
+    let dir = "override_args_dir";
+
+    at.mkdir(dir);
+    let fpath = at.plus(format!("{dir}/file"));
+    std::fs::File::create(fpath)
+        .expect("cannot create test file")
+        .set_len(100_000_000)
+        .expect("cannot set file size");
+
+    let fpath2 = at.plus(format!("{dir}/file_2"));
+    std::fs::File::create(fpath2)
+        .expect("cannot create test file")
+        .set_len(100_000_000)
+        .expect("cannot set file size");
+
+    let test_cases = [
+        (["-sb", "-m"], ["-sm", "--apparent-size"]),
+        (["-sb", "-k"], ["-sk", "--apparent-size"]),
+    ];
+
+    for (idx, (overwriting_args, expected)) in test_cases.into_iter().enumerate() {
+        let overridden_args = ts
+            .ucmd()
+            .arg(dir)
+            .args(&overwriting_args)
+            .succeeds()
+            .stdout_move_str();
+
+        let single_args = ts
+            .ucmd()
+            .arg(dir)
+            .args(&expected)
+            .succeeds()
+            .stdout_move_str();
+
+        assert_eq!(
+            overridden_args, single_args,
+            "Overwriting the b flag should still leave --apparent-size active. Run: {idx}"
+        );
+    }
+}