Add warning for out-of-bounds page range in pdfly cat command (py-pdf#58)

Author: Zingzy

pdfly/cat.py

@@ -78,6 +78,20 @@ def main(
                 in_fs[filename] = open(filename, "rb")
 
             reader = PdfReader(in_fs[filename])
+
+            num_pages = len(reader.pages)
+            start, end, step = page_range.indices(num_pages)
+            if (
+                start < 0
+                or end < 0
+                or start >= num_pages
+                or end > num_pages
+                or start > end
+            ):
+                print(
+                    f"WARNING: Page range {page_range} is out of bounds",
+                    file=sys.stderr,
+                )
             if not use_complements:
                 for page_num in range(*page_range.indices(len(reader.pages))):
                     writer.add_page(reader.pages[page_num])
@@ -87,7 +101,6 @@ def main(
                 compl_page_nums = all_page_nums - page_nums
                 for page_num in compl_page_nums:
                     writer.add_page(reader.pages[page_num])
-
         writer.write(output_fh)
     except Exception:
         print(traceback.format_exc(), file=sys.stderr)

tests/test_cat.py

@@ -71,7 +71,6 @@ def test_cat_subset_invalid_args(capsys, tmp_path, page_range):
     assert "Invalid file path or page range provided" in captured.err
 
 
-@pytest.mark.skip(reason="This check is not implemented yet")
 def test_cat_subset_warn_on_missing_pages(capsys, tmp_path):
     with chdir(tmp_path):
         exit_code = run_cli(
@@ -85,7 +84,7 @@ def test_cat_subset_warn_on_missing_pages(capsys, tmp_path):
         )
     captured = capsys.readouterr()
     assert exit_code == 0, captured
-    assert "WARN" in captured.out
+    assert "WARN" in captured.err
 
 
 @pytest.mark.xfail()  # There is currently a bug there