bpo-31553: add --json-lines option to json.tool

Doc/library/json.rst

@@ -714,6 +714,12 @@ Command line options
 
    .. versionadded:: 3.5
 
+.. cmdoption:: --json-lines
+
+   Parse every input line as separate JSON object.
+
+   .. versionadded:: 3.8
+
 .. cmdoption:: -h, --help
 
    Show the help message.

Doc/whatsnew/3.8.rst

@@ -135,6 +135,12 @@ by right-clicking the button.  (Contributed by Tal Einat in :issue:`1529353`.)
 The changes above have been backported to 3.7 maintenance releases.
 
 
+json.tool
+---------
+
+Add option ``--json-lines`` to parse every input line as separate JSON object.
+(Contributed by Weipeng Hong in :issue:`31553`.)
+
 os.path
 -------
 

Lib/json/tool.py

@@ -26,19 +26,25 @@ def main():
                         help='write the output of infile to outfile')
     parser.add_argument('--sort-keys', action='store_true', default=False,
                         help='sort the output of dictionaries alphabetically by key')
+    parser.add_argument('--json-lines', action='store_true', default=False,
+                        help='parse input using the jsonlines format')
     options = parser.parse_args()
 
     infile = options.infile or sys.stdin
     outfile = options.outfile or sys.stdout
     sort_keys = options.sort_keys
-    with infile:
+    json_lines = options.json_lines
+    with infile, outfile:
         try:
-            obj = json.load(infile)
+            if json_lines:
+                objs = (json.loads(line) for line in infile)
+            else:
+                objs = (json.load(infile), )
+            for obj in objs:
+                json.dump(obj, outfile, sort_keys=sort_keys, indent=4)
+                outfile.write('\n')
         except ValueError as e:
             raise SystemExit(e)
-    with outfile:
-        json.dump(obj, outfile, sort_keys=sort_keys, indent=4)
-        outfile.write('\n')
 
 
 if __name__ == '__main__':

Lib/test/test_json/test_tool.py

@@ -60,6 +60,28 @@ class TestTool(unittest.TestCase):
     ]
     """)
 
+    jsonlines_raw = textwrap.dedent("""\
+    {"ingredients":["frog", "water", "chocolate", "glucose"]}
+    {"ingredients":["chocolate","steel bolts"]}
+    """)
+
+    jsonlines_expect = textwrap.dedent("""\
+    {
+        "ingredients": [
+            "frog",
+            "water",
+            "chocolate",
+            "glucose"
+        ]
+    }
+    {
+        "ingredients": [
+            "chocolate",
+            "steel bolts"
+        ]
+    }
+    """)
+
     def test_stdin_stdout(self):
         args = sys.executable, '-m', 'json.tool'
         with Popen(args, stdin=PIPE, stdout=PIPE, stderr=PIPE) as proc:
@@ -92,6 +114,13 @@ def test_infile_outfile(self):
         self.assertEqual(out, b'')
         self.assertEqual(err, b'')
 
+    def test_jsonlines(self):
+        args = sys.executable, '-m', 'json.tool', '--json-lines'
+        with Popen(args, stdin=PIPE, stdout=PIPE, stderr=PIPE) as proc:
+            out, err = proc.communicate(self.jsonlines_raw.encode())
+        self.assertEqual(out.splitlines(), self.jsonlines_expect.encode().splitlines())
+        self.assertEqual(err, b'')
+
     def test_help_flag(self):
         rc, out, err = assert_python_ok('-m', 'json.tool', '-h')
         self.assertEqual(rc, 0)

Misc/NEWS.d/next/Library/2018-10-23-14-46-47.bpo-31553.JxRkAW.rst

@@ -0,0 +1 @@
+Add the --json-lines option to json.tool. Patch by hongweipeng.