From 3675ae918cf4e91b4fed9a237350c2c0f7a5d1aa Mon Sep 17 00:00:00 2001
From: "James R. Barlow" <james@purplerock.ca>
Date: Tue, 22 Dec 2020 01:22:14 -0800
Subject: [PATCH] Fix certain invalid page ranges causing exception

Closes #686
---
 src/ocrmypdf/_validation.py | 19 ++++++++++++++-----
 tests/test_page_numbers.py  |  6 ++++++
 2 files changed, 20 insertions(+), 5 deletions(-)

diff --git a/src/ocrmypdf/_validation.py b/src/ocrmypdf/_validation.py
index 9354a629..a6ee9a08 100644
--- a/src/ocrmypdf/_validation.py
+++ b/src/ocrmypdf/_validation.py
@@ -13,7 +13,7 @@ import sys
 import unicodedata
 from pathlib import Path
 from shutil import copyfileobj
-from typing import Tuple
+from typing import List, Set, Tuple, Union
 
 import pikepdf
 import PIL
@@ -136,10 +136,10 @@ def check_options_preprocessing(options):
             raise BadArgsError(str(e))
 
 
-def _pages_from_ranges(ranges):
+def _pages_from_ranges(ranges: str) -> Set[int]:
     if is_iterable_notstr(ranges):
         return set(ranges)
-    pages = []
+    pages: List[int] = []
     page_groups = ranges.replace(' ', '').split(',')
     for g in page_groups:
         if not g:
@@ -150,9 +150,18 @@ def _pages_from_ranges(ranges):
             pages.append(int(g) - 1)
         else:
             try:
-                pages.extend(range(int(start) - 1, int(end)))
+                new_pages = list(range(int(start) - 1, int(end)))
+                if not new_pages:
+                    raise BadArgsError(f"invalid page subrange '{start}-{end}'")
+                pages.extend(new_pages)
             except ValueError:
-                raise BadArgsError("invalid page range")
+                raise BadArgsError("invalid page range") from None
+
+    if not pages:
+        raise BadArgsError(
+            f"The string of page ranges '{ranges}' did not contain any recognizable "
+            f"page ranges."
+        )
 
     if not monotonic(pages):
         log.warning(
diff --git a/tests/test_page_numbers.py b/tests/test_page_numbers.py
index 28f59416..71f06a0d 100644
--- a/tests/test_page_numbers.py
+++ b/tests/test_page_numbers.py
@@ -28,6 +28,12 @@ from ocrmypdf.pdfinfo import PdfInfo
         ['1,3,-11', BadArgsError],
         ['1-,', BadArgsError],
         ['start-end', BadArgsError],
+        ['1-0', BadArgsError],
+        ['99-98', BadArgsError],
+        ['0-0', BadArgsError],
+        ['1-0,3-4', BadArgsError],
+        [',', BadArgsError],
+        ['', BadArgsError],
     ],
 )
 def test_pages(pages, result):