numfmt: round values printed without a suffix

src/uu/numfmt/src/format.rs

@@ -584,8 +584,18 @@ fn consider_suffix(
         Unit::None => return Ok((n, None)),
     };
 
+    // The suffix is chosen from the value as it will be printed, so with
+    // `--round=down` 999.9 stays 999 instead of becoming 0.9k.
+    let unscaled = if is_precision_specified {
+        round_with_precision(n, round_method, 0)
+    } else {
+        div_round(n, 1.0, round_method)
+    };
+    if unscaled.abs() <= bases[1] - 1.0 {
+        return Ok((unscaled, None));
+    }
+
     let i = match abs_n {
-        _ if abs_n <= bases[1] - 1.0 => return Ok((n, None)),
         _ if abs_n < bases[2] => 1,
         _ if abs_n < bases[3] => 2,
         _ if abs_n < bases[4] => 3,

tests/by-util/test_numfmt.rs

@@ -616,6 +616,44 @@ fn test_round_with_to_unit() {
     }
 }
 
+#[test]
+fn test_round_without_suffix() {
+    // A value printed without a suffix is rounded with the method too, and
+    // the suffix is only added if the rounded value needs one.
+    for (method, exp) in [
+        ("from-zero", ["13", "-13", "1.0k", "1.0K"]),
+        ("towards-zero", ["12", "-12", "999", "1023"]),
+        ("up", ["13", "-12", "1.0k", "1.0K"]),
+        ("down", ["12", "-13", "999", "1023"]),
+        ("nearest", ["12", "-12", "1.0k", "1.0K"]),
+    ] {
+        let round = format!("--round={method}");
+        new_ucmd!()
+            .args(&["--to=si", &round, "--", "12.1", "-12.1", "999.9"])
+            .succeeds()
+            .stdout_only(exp[..3].join("\n") + "\n");
+        new_ucmd!()
+            .args(&["--to=iec", &round, "1023.9"])
+            .succeeds()
+            .stdout_only(format!("{}\n", exp[3]));
+    }
+
+    // With a `--format` precision, the value is rounded to an integer first.
+    for (method, exp) in [
+        ("from-zero", "13.0\n-13.0\n1.0k\n2.0\n"),
+        ("towards-zero", "12.0\n-12.0\n999.0\n1.0\n"),
+        ("up", "13.0\n-12.0\n1.0k\n2.0\n"),
+        ("down", "12.0\n-13.0\n999.0\n1.0\n"),
+        ("nearest", "12.0\n-12.0\n1.0k\n1.0\n"),
+    ] {
+        new_ucmd!()
+            .args(&["--to=si", "--format=%.1f", &format!("--round={method}")])
+            .args(&["--", "12.1", "-12.1", "999.9", "1.44"])
+            .succeeds()
+            .stdout_only(exp);
+    }
+}
+
 #[test]
 fn test_to_unit_with_unitless_small_value_uses_display_rounding() {
     new_ucmd!()