Add code to write info.json output to stdout when option -output is used with a dash: -o -

test/test_write_info_json.py

@@ -67,6 +67,26 @@ class TestInfoJSON(unittest.TestCase):
             descr = descf.read()
         self.assertEqual(descr, EXPECTED_DESCRIPTION)
 
+    def test_info_json_with_stdout_as_output_returns_good_json(self):
+        from unittest.mock import patch
+        from io import StringIO
+        params['writedescription'] = False
+        params['quiet'] = True
+        params['outtmpl'] = '-'
+        with patch('sys.stdout', new_callable=StringIO) as mock_stdout:
+            ie = youtube_dl.extractor.YoutubeIE()
+            ydl = YoutubeDL(params)
+            ydl.add_info_extractor(ie)
+            ydl.download([TEST_ID])
+            output = mock_stdout.getvalue()
+            jd = json.loads(output)
+        self.assertEqual(jd['upload_date'], u'20121002')
+        self.assertEqual(jd['description'], EXPECTED_DESCRIPTION)
+        self.assertEqual(jd['id'], TEST_ID)
+        self.assertEqual(jd['extractor'], 'youtube')
+        self.assertEqual(jd['title'], u'''youtube-dl test video "'/\ä↭𝕐''')
+        self.assertEqual(jd['uploader'], 'Philipp Hagemeister')
+
     def tearDown(self):
         if os.path.exists(INFO_JSON_FILE):
             os.remove(INFO_JSON_FILE)

youtube_dl/utils.py

@@ -200,14 +200,21 @@ else:
 
 # In Python 2.x, json.dump expects a bytestream.
 # In Python 3.x, it writes to a character stream
-if sys.version_info < (3,0):
+# if user passed '-' as outputname, redirect output to stdout
+if sys.version_info < (3, 0):
     def write_json_file(obj, fn):
-        with open(fn, 'wb') as f:
-            json.dump(obj, f)
+        if fn.rstrip('.info.json') == u'-':
+            json.dump(obj, sys.stdout)
+        else:
+            with open(fn, 'wb') as f:
+                json.dump(obj, f)
 else:
     def write_json_file(obj, fn):
-        with open(fn, 'w', encoding='utf-8') as f:
-            json.dump(obj, f)
+        if fn.rstrip('.info.json') == u'-':
+            json.dump(obj, sys.stdout)
+        else:
+            with open(fn, 'w', encoding='utf-8') as f:
+                json.dump(obj, f)
 
 if sys.version_info >= (2,7):
     def find_xpath_attr(node, xpath, key, val):