[postprocessor:metadata] handle dicts in mode;tags (fixes #1598)

gallery_dl/postprocessor/metadata.py

@@ -102,11 +102,17 @@ class MetadataPP(PostProcessor):
         if not tags:
             return
 
-        if not isinstance(tags, list):
+        if isinstance(tags, str):
             taglist = tags.split(", ")
             if len(taglist) < len(tags) / 16:
                 taglist = tags.split(" ")
             tags = taglist
+        elif isinstance(tags, dict):
+            taglists = tags.values()
+            tags = []
+            extend = tags.extend
+            for taglist in taglists:
+                extend(taglist)
 
         fp.write("\n".join(tags) + "\n")
 

test/test_postprocessor.py

@@ -30,9 +30,9 @@ class MockPostprocessorModule(Mock):
 
 class FakeJob():
 
-    def __init__(self):
-        self.extractor = extractor.find("test:")
-        self.pathfmt = util.PathFormat(self.extractor)
+    def __init__(self, extr=extractor.find("test:")):
+        self.extractor = extr
+        self.pathfmt = util.PathFormat(extr)
         self.out = output.NullOutput()
         self.get_logger = logging.getLogger
         self.hooks = collections.defaultdict(list)
@@ -243,6 +243,15 @@ class MetadataTest(BasePostprocessorTest):
             self._trigger()
         self.assertEqual(self._output(m), "foo\nbar\nbaz\n")
 
+    def test_metadata_tags_dict(self):
+        self._create(
+            {"mode": "tags"},
+            {"tags": {"g": ["foobar1", "foobar2"], "m": ["foobarbaz"]}},
+        )
+        with patch("builtins.open", mock_open()) as m:
+            self._trigger()
+        self.assertEqual(self._output(m), "foobar1\nfoobar2\nfoobarbaz\n")
+
     def test_metadata_custom(self):
         def test(pp_info):
             pp = self._create(pp_info, {"foo": "bar"})