From 15afe874efaa72eac81af32cf13fba2ff0c9af17 Mon Sep 17 00:00:00 2001
From: Qrytics <qrtyics@gmail.com>
Date: Tue, 10 Nov 2026 04:13:15 -0600
Subject: [PATCH] Read CLI JSON inputs as utf-8-sig so BOM files do not crash

---
 jsonpatch_cli.py |  8 ++++----
 tests.py         | 23 +++++++++++++++++++++++
 2 files changed, 27 insertions(+), 4 deletions(-)

diff --git a/jsonpatch_cli.py b/jsonpatch_cli.py
index e3697e3..f0d5bf2 100644
--- a/jsonpatch_cli.py
+++ b/jsonpatch_cli.py
@@ -13,8 +13,8 @@
 
 jsondiff_parser = argparse.ArgumentParser(
     prog='jsondiff', description='Diff two JSON files')
-jsondiff_parser.add_argument('FILE1', type=argparse.FileType('r', encoding='utf-8'))
-jsondiff_parser.add_argument('FILE2', type=argparse.FileType('r', encoding='utf-8'))
+jsondiff_parser.add_argument('FILE1', type=argparse.FileType('r', encoding='utf-8-sig'))
+jsondiff_parser.add_argument('FILE2', type=argparse.FileType('r', encoding='utf-8-sig'))
 jsondiff_parser.add_argument('--indent', type=int, default=None,
                              help='Indent output by n spaces')
 jsondiff_parser.add_argument('-u', '--preserve-unicode', action='store_true',
@@ -51,9 +51,9 @@ def diff_files():
 jsonpatch_parser = argparse.ArgumentParser(
     prog='jsonpatch',
     description='Apply a JSON patch on a JSON file')
-jsonpatch_parser.add_argument('ORIGINAL', type=argparse.FileType('r', encoding='utf-8'),
+jsonpatch_parser.add_argument('ORIGINAL', type=argparse.FileType('r', encoding='utf-8-sig'),
                               help='Original file')
-jsonpatch_parser.add_argument('PATCH', type=argparse.FileType('r', encoding='utf-8'),
+jsonpatch_parser.add_argument('PATCH', type=argparse.FileType('r', encoding='utf-8-sig'),
                               nargs='?', default=sys.stdin,
                               help='Patch file (read from stdin if omitted)')
 jsonpatch_parser.add_argument('--indent', type=int, default=None,
diff --git a/tests.py b/tests.py
index e124a96..0149225 100644
--- a/tests.py
+++ b/tests.py
@@ -3148,6 +3148,29 @@ def test_jsondiff_utf8_files_without_utf8_mode(self):
         self.assertEqual(jsonpatch.apply_patch(self.read(src), patch),
                          self.read(dst))
 
+    def test_jsondiff_utf8_bom_files(self):
+        for path, value in (('a.json', {'a': 1}), ('b.json', {'a': 2})):
+            with open(os.path.join(self.dir, path), 'w', encoding='utf-8-sig') as f:
+                json.dump(value, f)
+        src = os.path.join(self.dir, 'a.json')
+        dst = os.path.join(self.dir, 'b.json')
+        res = self.run_script('jsondiff', src, dst)
+        # like diff, it exits with 1 if the files differ
+        self.assertEqual(res.returncode, 1, res.stderr)
+        patch = json.loads(res.stdout)
+        self.assertEqual(jsonpatch.apply_patch({'a': 1}, patch), {'a': 2})
+
+    def test_jsonpatch_utf8_bom_files(self):
+        doc = os.path.join(self.dir, 'doc.json')
+        patch = os.path.join(self.dir, 'patch.json')
+        with open(doc, 'w', encoding='utf-8-sig') as f:
+            json.dump({'a': 1}, f)
+        with open(patch, 'w', encoding='utf-8-sig') as f:
+            json.dump([{'op': 'replace', 'path': '/a', 'value': 2}], f)
+        res = self.run_script('jsonpatch', doc, patch)
+        self.assertEqual(res.returncode, 0, res.stderr)
+        self.assertEqual(json.loads(res.stdout), {'a': 2})
+
     def test_jsonpatch(self):
         doc = self.write('doc.json', {'a': [1, 2], 'b': 0})
         patch = self.write('patch.json', [{'op': 'add', 'path': '/a/-', 'value': 3},