From 51b976da439be272db8c044c7ba8856bca1399ff Mon Sep 17 00:00:00 2001
From: Hugo van Kemenade <1324225+hugovk@users.noreply.github.com>
Date: Thu, 23 Apr 2026 18:27:02 +0300
Subject: [PATCH] gh-132631: Fix "I/O operation on closed file" when parsing
 JSON Lines file (GH-132632) (cherry picked from commit
 42d645a7e81e0a5e6e0d35e222a8520450ac28ef)

Co-authored-by: Hugo van Kemenade <1324225+hugovk@users.noreply.github.com>
Co-authored-by: Brian Schubert <brianm.schubert@gmail.com>
---
 Lib/json/tool.py                                         | 3 ++-
 Lib/test/test_json/json_lines.jsonl                      | 2 ++
 Lib/test/test_json/test_tool.py                          | 9 +++++++++
 .../2025-04-17-15-26-35.gh-issue-132631.IDFZfb.rst       | 2 ++
 4 files changed, 15 insertions(+), 1 deletion(-)
 create mode 100644 Lib/test/test_json/json_lines.jsonl
 create mode 100644 Misc/NEWS.d/next/Library/2025-04-17-15-26-35.gh-issue-132631.IDFZfb.rst

diff --git a/Lib/json/tool.py b/Lib/json/tool.py
index 1967817add8abc..0cabbdba85a155 100644
--- a/Lib/json/tool.py
+++ b/Lib/json/tool.py
@@ -88,7 +88,8 @@ def main():
             infile = open(options.infile, encoding='utf-8')
         try:
             if options.json_lines:
-                objs = (json.loads(line) for line in infile)
+                lines = infile.readlines()
+                objs = (json.loads(line) for line in lines)
             else:
                 objs = (json.load(infile),)
         finally:
diff --git a/Lib/test/test_json/json_lines.jsonl b/Lib/test/test_json/json_lines.jsonl
new file mode 100644
index 00000000000000..d2f292111956f3
--- /dev/null
+++ b/Lib/test/test_json/json_lines.jsonl
@@ -0,0 +1,2 @@
+{"ingredients":["frog", "water", "chocolate", "glucose"]}
+{"ingredients":["chocolate","steel bolts"]}
diff --git a/Lib/test/test_json/test_tool.py b/Lib/test/test_json/test_tool.py
index 7b5d217a21558c..0a96b318b15b1c 100644
--- a/Lib/test/test_json/test_tool.py
+++ b/Lib/test/test_json/test_tool.py
@@ -1,4 +1,5 @@
 import errno
+import pathlib
 import os
 import sys
 import textwrap
@@ -157,6 +158,14 @@ def test_jsonlines(self):
         self.assertEqual(process.stdout, self.jsonlines_expect)
         self.assertEqual(process.stderr, '')
 
+    @force_not_colorized
+    def test_jsonlines_from_file(self):
+        jsonl = pathlib.Path(__file__).parent / 'json_lines.jsonl'
+        args = sys.executable, '-m', self.module, '--json-lines', jsonl
+        process = subprocess.run(args, capture_output=True, text=True, check=True)
+        self.assertEqual(process.stdout, self.jsonlines_expect)
+        self.assertEqual(process.stderr, '')
+
     def test_help_flag(self):
         rc, out, err = assert_python_ok('-m', self.module, '-h',
                                         PYTHON_COLORS='0')
diff --git a/Misc/NEWS.d/next/Library/2025-04-17-15-26-35.gh-issue-132631.IDFZfb.rst b/Misc/NEWS.d/next/Library/2025-04-17-15-26-35.gh-issue-132631.IDFZfb.rst
new file mode 100644
index 00000000000000..9cc1d5a389c085
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2025-04-17-15-26-35.gh-issue-132631.IDFZfb.rst
@@ -0,0 +1,2 @@
+Fix "I/O operation on closed file" when parsing JSON Lines file with
+:mod:`JSON CLI <json.tool>`.