From 8cb8bc309ed3ff6c410c1f42af0a3d90c33f230b Mon Sep 17 00:00:00 2001
From: jwalith4418-Mj <232281058+jwalith4418-Mj@users.noreply.github.com>
Date: Mon, 2 Nov 2026 00:46:54 +0530
Subject: [PATCH] Reject non-finite numbers in JSON CLI output

Pass allow_nan=False for --as-json and report encoding errors without emitting invalid JSON. Keep default JSON5 non-finite output supported.

Prepared with AI assistance; contributor review is required before upload.
---
 json5/tool.py      | 21 +++++++++++++--------
 tests/tool_test.py |  9 +++++++++
 2 files changed, 22 insertions(+), 8 deletions(-)

diff --git a/json5/tool.py b/json5/tool.py
index a778593..c5fb34c 100644
--- a/json5/tool.py
+++ b/json5/tool.py
@@ -66,13 +66,18 @@ def main(argv=None, host=None):
         args.quote_style = json5.QuoteStyle.ALWAYS_DOUBLE.value
 
     obj = json5.loads(inp, strict=args.strict)
-    s = json5.dumps(
-        obj,
-        indent=args.indent,
-        quote_keys=args.quote_keys,
-        trailing_commas=args.trailing_commas,
-        quote_style=QUOTE_STYLES[args.quote_style],
-    )
+    try:
+        s = json5.dumps(
+            obj,
+            indent=args.indent,
+            quote_keys=args.quote_keys,
+            trailing_commas=args.trailing_commas,
+            quote_style=QUOTE_STYLES[args.quote_style],
+            allow_nan=not args.as_json,
+        )
+    except ValueError as error:
+        host.print(str(error), file=host.stderr)
+        return 1
     host.print(s)
     return 0
 
@@ -126,7 +131,7 @@ def _parse_args(host, argv):
         action='store_const',
         const=True,
         default=False,
-        help='output as JSON (same as --quote-keys --no-trailing-commas)',
+        help='output as JSON (reject non-finite numbers)',
     )
     parser.add_argument(
         '--indent',
diff --git a/tests/tool_test.py b/tests/tool_test.py
index 730930a..a200b27 100644
--- a/tests/tool_test.py
+++ b/tests/tool_test.py
@@ -149,6 +149,15 @@ def test_as_json(self):
             out='"\\u0000\\u000b"\n',
         )
 
+    def test_as_json_nonfinite(self):
+        self.check(
+            ['--as-json', '-c', '{value: NaN}'],
+            returncode=1,
+            out='',
+            err='Illegal JSON5 value: nan\n',
+        )
+        self.check(['-c', 'NaN'], out='NaN\n')
+
     def test_quote_keys(self):
         self.check(
             ['--quote-keys', '-c', '{foo: 1}'],