server/tags: allow deleting used tags

API.md

@@ -486,7 +486,6 @@ data.
 - **Errors**
 
     - the tag does not exist
-    - the tag is used by some posts
     - privileges are too low
 
 - **Description**

server/szurubooru/api/tag_api.py

@@ -90,10 +90,6 @@ class TagDetailApi(BaseApi):
 
     def delete(self, ctx, tag_name):
         tag = tags.get_tag_by_name(tag_name)
-        if tag.post_count > 0:
-            raise tags.TagIsInUseError(
-                'Tag has some usages and cannot be deleted. ' +
-                'Please untag relevant posts first.')
         auth.verify_privilege(ctx.user, 'tags:delete')
         snapshots.save_entity_deletion(tag, ctx.user)
         tags.delete(tag)

server/szurubooru/tests/api/test_tag_deleting.py

@@ -31,18 +31,19 @@ def test_deleting(test_ctx):
     assert db.session.query(db.Tag).count() == 0
     assert os.path.exists(os.path.join(config.config['data_dir'], 'tags.json'))
 
-def test_trying_to_delete_used(test_ctx, post_factory):
+def test_deleting_used(test_ctx, post_factory):
     tag = test_ctx.tag_factory(names=['tag'])
     post = post_factory()
     post.tags.append(tag)
     db.session.add_all([tag, post])
     db.session.commit()
-    with pytest.raises(tags.TagIsInUseError):
     test_ctx.api.delete(
         test_ctx.context_factory(
             user=test_ctx.user_factory(rank=db.User.RANK_REGULAR)),
         'tag')
-    assert db.session.query(db.Tag).count() == 1
+    db.session.refresh(post)
+    assert db.session.query(db.Tag).count() == 0
+    assert post.tags == []
 
 def test_trying_to_delete_non_existing(test_ctx):
     with pytest.raises(tags.TagNotFoundError):