Allow --trim-filenames=0 and update tests

test/test_YoutubeDL.py

@@ -717,7 +717,7 @@ class TestYoutubeDL(unittest.TestCase):
             ydl._num_downloads = 1
             self.assertEqual(ydl.validate_outtmpl(tmpl), None)
 
-            out = ydl.evaluate_outtmpl(tmpl, info or self.outtmpl_info)
+            out = ydl.evaluate_outtmpl_for_filename(tmpl, info or self.outtmpl_info)
             fname = ydl.prepare_filename(info or self.outtmpl_info)
 
             if not isinstance(expected, (list, tuple)):
@@ -791,7 +791,7 @@ class TestYoutubeDL(unittest.TestCase):
                 self.assertEqual(got_dict.get(info_field), expected, info_field)
             return True
 
-        test('%()j', (expect_same_infodict, None))
+        test('%()j', (expect_same_infodict, None), trim_file_name=0)
 
         # NA placeholder
         NA_TEST_OUTTMPL = '%(uploader_date)s-%(width)d-%(x|def)s-%(id)s.%(ext)s'

yt_dlp/YoutubeDL.py

@@ -1458,10 +1458,16 @@ class YoutubeDL:
             else:
                 raise ValueError("--trim-filenames must end with 'b' or 'c'")
 
-        max_file_name = self.params.get('trim_file_name') or DEFAULT_MAX_FILE_NAME
+        max_file_name = self.params.get('trim_file_name')
+        if max_file_name is None:
+            max_file_name = DEFAULT_MAX_FILE_NAME
         mode, max_file_name = parse_max_file_name(max_file_name)
-        if max_file_name < 1:
+        if max_file_name < 0:
             raise ValueError('Invalid --trim-filenames specified')
+        if max_file_name == 0:
+            # no maximum
+            return filename + suffix
+
         encoding = self.params.get('filesystem_encoding') or sys.getfilesystemencoding()
 
         def trim_filename(name: str, length: int):