Add synonym handling for tags

This fixes #247, but can be used handle other synonyms in the future.

tildes/tests/test_topic_tags.py

@@ -36,3 +36,9 @@ def test_tags_lowercased(text_topic):
     """Ensure tags get converted to lowercase."""
     text_topic.tags = ["ONE", "Two", "thRee"]
     assert text_topic.tags == ["one", "two", "three"]
+
+
+def test_tags_synonyms(text_topic):
+    """ Ensure synonyms are replaced."""
+    text_topic.tags = ["spoilers"]
+    assert text_topic.tags == ["spoiler"]

tildes/tildes/schemas/topic.py

@@ -16,6 +16,7 @@ from tildes.schemas.group import GroupSchema
 from tildes.schemas.user import UserSchema
 
 TITLE_MAX_LENGTH = 200
+TAG_SYNONYMS = {"spoiler": ["spoilers"]}
 
 
 class TopicSchema(Schema):
@@ -57,6 +58,11 @@ class TopicSchema(Schema):
             if not tag or tag.isspace():
                 continue
 
+            # handle synonyms
+            for name, synonyms in TAG_SYNONYMS.items():
+                if tag in synonyms:
+                    tag = name
+
             # skip any duplicate tags
             if tag in tags:
                 continue