[twitter] extract alt texts as 'description' (closes #2617)

gallery_dl/extractor/twitter.py

@@ -104,6 +104,7 @@ class TwitterExtractor(Extractor):
 
     def _extract_media(self, tweet, entities, files):
         for media in entities:
+            descr = media.get("ext_alt_text")
             width = media["original_info"].get("width", 0)
             height = media["original_info"].get("height", 0)
 
@@ -115,6 +116,7 @@ class TwitterExtractor(Extractor):
                         "width"      : width,
                         "height"     : height,
                         "extension"  : None,
+                        "description": descr,
                     })
                 elif self.videos:
                     video_info = media["video_info"]
@@ -129,6 +131,7 @@ class TwitterExtractor(Extractor):
                         "bitrate"    : variant.get("bitrate", 0),
                         "duration"   : video_info.get(
                             "duration_millis", 0) / 1000,
+                        "description": descr,
                     })
             elif "media_url_https" in media:
                 url = media["media_url_https"]
@@ -139,6 +142,7 @@ class TwitterExtractor(Extractor):
                     "width"      : width,
                     "height"     : height,
                     "_fallback"  : self._image_fallback(base),
+                    "description": descr,
                 }))
             else:
                 files.append({"url": media["media_url"]})
@@ -711,6 +715,10 @@ class TwitterTweetExtractor(TwitterExtractor):
             "options": (("syndication", True),),
             "count": 1,
         }),
+        # media alt texts / descriptions (#2617)
+        ("https://twitter.com/my0nruri/status/1528379296041299968", {
+            "keyword": {"description": "oc"}
+        }),
     )
 
     def __init__(self, match):