[reddit] add 'previews' option (#4322)

another way to disable this new behavior

docs/configuration.rst

@@ -2716,6 +2716,17 @@ Description
  Ignore all submissions posted before/after the submission with this ID.
 
 
+extractor.reddit.previews
+-------------------------
+Type
+ ``bool``
+Default
+ ``true``
+Description
+ For failed downloads from external URLs / child extractors,
+ download Reddit's preview image/video if available.
+
+
 extractor.reddit.recursion
 --------------------------
 Type

gallery_dl/extractor/reddit.py

@@ -30,6 +30,7 @@ def items(self):
 
  parentdir = self.config("parent-directory")
  max_depth = self.config("recursion", 0)
+ previews = self.config("previews", True)
 
  videos = self.config("videos", True)
  if videos:
@@ -119,7 +120,7 @@ def items(self):
  if match:
  extra.append(match.group(1))
  elif not match_user(url) and not match_subreddit(url):
- if "preview" in data:
+ if previews and "preview" in data:
  data["_fallback"] = self._previews(data)
  yield Message.Queue, text.unescape(url), data
  if "_fallback" in data: