Add validation for --line-ranges values

src/black/ranges.py

@@ -36,6 +36,16 @@ def parse_line_ranges(line_ranges: Sequence[str]) -> list[tuple[int, int]]:
                 f" {lines_str!r}"
             ) from None
         else:
+            if start < 1 or end < 1:
+                raise ValueError(
+                    "Incorrect --line-ranges value, "
+                    f"expect positive integers, found {lines_str!r}"
+                )
+            if start > end:
+                raise ValueError(
+                    "Incorrect --line-ranges value, expect START <= END, "
+                    f"found {lines_str!r}"
+                )
             lines.append((start, end))
     return lines
 

tests/test_ranges.py

@@ -2,7 +2,33 @@
 
 import pytest
 
-from black.ranges import adjusted_lines, sanitized_lines
+from black.ranges import adjusted_lines, parse_line_ranges, sanitized_lines
+
+
+@pytest.mark.parametrize(
+    "lines_str, expected",
+    [
+        (["1-5"], [(1, 5)]),
+        (["1-1"], [(1, 1)]),
+        (["1-3", "5-7"], [(1, 3), (5, 7)]),
+    ],
+)
+def test_parse_line_ranges_valid(lines_str, expected):
+    assert parse_line_ranges(lines_str) == expected
+
+
+@pytest.mark.parametrize(
+    "lines_str",
+    [
+        ["5-3"],
+        ["0-5"],
+        ["-1-5"],
+        ["5-0"],
+    ],
+)
+def test_parse_line_ranges_invalid(lines_str):
+    with pytest.raises(ValueError, match="Incorrect --line-ranges"):
+        parse_line_ranges(lines_str)
 
 
 @pytest.mark.parametrize(