[core] Fix `simulate` changing format selection

test/test_YoutubeDL.py

@@ -4,6 +4,7 @@
 import os
 import sys
 import unittest
+from unittest.mock import patch
 
 sys.path.insert(0, os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
 
@@ -521,7 +522,32 @@ class TestFormatSelection(unittest.TestCase):
             pass
         self.assertEqual(ydl.downloaded_info_dicts, [])
 
-    def test_default_format_spec(self):
+    @patch('yt_dlp.postprocessor.ffmpeg.FFmpegMergerPP.available', False)
+    def test_default_format_spec_without_ffmpeg(self):
+        ydl = YDL({})
+        self.assertEqual(ydl._default_format_spec({}), 'best/bestvideo+bestaudio')
+
+        ydl = YDL({'simulate': True})
+        self.assertEqual(ydl._default_format_spec({}), 'best/bestvideo+bestaudio')
+
+        ydl = YDL({})
+        self.assertEqual(ydl._default_format_spec({'is_live': True}), 'best/bestvideo+bestaudio')
+
+        ydl = YDL({'simulate': True})
+        self.assertEqual(ydl._default_format_spec({'is_live': True}), 'best/bestvideo+bestaudio')
+
+        ydl = YDL({'outtmpl': '-'})
+        self.assertEqual(ydl._default_format_spec({}), 'best/bestvideo+bestaudio')
+
+        ydl = YDL({})
+        self.assertEqual(ydl._default_format_spec({}, download=False), 'bestvideo*+bestaudio/best')
+        self.assertEqual(ydl._default_format_spec({'is_live': True}), 'best/bestvideo+bestaudio')
+
+    @patch('yt_dlp.postprocessor.ffmpeg.FFmpegMergerPP.available', True)
+    def test_default_format_spec_with_ffmpeg(self):
+        ydl = YDL({})
+        self.assertEqual(ydl._default_format_spec({}), 'bestvideo*+bestaudio/best')
+
         ydl = YDL({'simulate': True})
         self.assertEqual(ydl._default_format_spec({}), 'bestvideo*+bestaudio/best')
 
@@ -529,7 +555,7 @@ class TestFormatSelection(unittest.TestCase):
         self.assertEqual(ydl._default_format_spec({'is_live': True}), 'best/bestvideo+bestaudio')
 
         ydl = YDL({'simulate': True})
-        self.assertEqual(ydl._default_format_spec({'is_live': True}), 'bestvideo*+bestaudio/best')
+        self.assertEqual(ydl._default_format_spec({'is_live': True}), 'best/bestvideo+bestaudio')
 
         ydl = YDL({'outtmpl': '-'})
         self.assertEqual(ydl._default_format_spec({}), 'best/bestvideo+bestaudio')

yt_dlp/YoutubeDL.py

@@ -2172,7 +2172,6 @@ class YoutubeDL:
         }))
 
     def _default_format_spec(self, info_dict, download=True):
-        download = download and not self.params.get('simulate')
         prefer_best = download and (
             self.params['outtmpl']['default'] == '-'
             or info_dict.get('is_live') and not self.params.get('live_from_start'))