[Sqlalchemy-tickets] Issue #3051: Calling setdefault on a MutableDict does not trigger change (zzzeek/sqlalchemy)

[John J. <iss...@bi...>]

New issue 3051: Calling setdefault on a MutableDict does not trigger change
https://bitbucket.org/zzzeek/sqlalchemy/issue/3051/calling-setdefault-on-a-mutabledict-does

John Jiang:

I'm using flask-sqlalchemy

```
#!python

class Data(db.Model):
    blob = db.Column(MutableDict.as_mutable(JSON), default={})

data.blob.setdefault('blah', {})
db.session.add(data)
db.session.commit()
```

blob does not save the changes.