[Qrytics]

Summary

jsondiff/jsonpatch crash with a raw traceback on UTF-8 BOM files (e.g. saved by Windows Notepad).

Repro

python -c "open('"'"'bom1.json'"'"','"'"'w'"'"',encoding='"'"'utf-8-sig'"'"').write('"'"'{\"a\": 1}'"'"')"
python -c "open('"'"'bom2.json'"'"','"'"'w'"'"',encoding='"'"'utf-8-sig'"'"').write('"'"'{\"a\": 2}'"'"')"
jsondiff bom1.json bom2.json

Expected: prints the patch [{"op": "replace", "path": "/a", "value": 2}] and exits 1 (documented diff-like contract). Actual before fix: json.decoder.JSONDecodeError: Unexpected UTF-8 BOM (decode using utf-8-sig), exit 1 with traceback. Same for jsonpatch with BOM inputs.

Root cause

jsonpatch_cli.py lines 16, 17 (jsondiff FILE1/FILE2), 54, 56 (jsonpatch ORIGINAL/PATCH): all four CLI inputs use argparse.FileType('"'"'r'"'"', encoding='"'"'utf-8'"'"'), which preserves the BOM as U+FEFF and makes json.load raise. utf-8-sig decodes BOM-less files byte-identically.

Fix

encoding='"'"'utf-8'"'"' -> encoding='"'"'utf-8-sig'"'"' in the four argparse.FileType declarations in jsonpatch_cli.py. No other code touched.

Tests

• New: tests.py::CommandLineTests::test_jsondiff_utf8_bom_files, ::test_jsonpatch_utf8_bom_files (existing ScriptRunner + temp-dir unittest style).
• Run: python -m pytest tests.py -k "utf8_bom or CommandLineTests" -q -> 27 passed, 1 skipped, 22 subtests passed (skip is pre-existing POSIX-only permissions test).
• Full tests.py: 336 passed, 1 skipped, plus 1 pre-existing failure in DocumentationTests::test_tutorial that fails identically on the untouched tree (verified via git stash).
• Lint: flake8 --select=E9,F63,F7,F82 clean on both touched files.