[Sqlalchemy-tickets] Issue #3646: MutableDict creates only on first level of JSON (zzzeek/sqlalchemy)

[Valentin K. <iss...@bi...>]

New issue 3646: MutableDict creates only on first level of JSON
https://bitbucket.org/zzzeek/sqlalchemy/issues/3646/mutabledict-creates-only-on-first-level-of

Valentin Kaplov:

If we associate MutableDict with JSON data, then MutableDict accociates with first level elements only. As result if we have on second and/or next levels mutable objects (like list, dict) and we modify them, then MutableDict will not marked as dirty/changed and modification will not take effect to database. Thus we'll lose consistency.
Example.
We have next JSON data from database:

```
#!python
{
    "key1": {"key1.2": "value1.2"},
    "key2": ["value2.1", "value2.2"],
    "key3": "value3",
}
```
If we pass the data to MutableDict, then it will create next object tree:

**Actual result:**
```
#!python

m_dict = MutableDict({
    "key1": dict({"key1.2": "value1.2"}),    # value builtin dict
    "key2": list(["value2.1", "value2.2"]),  # value builtin list
    "key3": "value3"
})

m_dict['key1']['key1.2'] = 'new_value'   # m_dict doesn't marked as changed
m_dict['key1'][0] = 'new_value'          # m_dict doesn't marked as changed
```


**Expected result:**
```
#!python

MutableDict({
    "key1": MutableDict({"key1.2": "value1.2"})      # value MutableDict asocciated with JSON
    "key2": MutableList(["value2.1", "value2.2"]),   # value MutableDict asocciated with JSON
    "key3": "value3"
})

m_dict['key1']['key1.2'] = 'new_value'   # m_dict marked as changed
m_dict['key1'][0] = 'new_value'          # m_dict marked as changed
```

**Additional information:**
To fix the problem needs to have implemented MutableList https://bitbucket.org/zzzeek/sqlalchemy/issues/3297

Need to change all builtin mutables in JSON on corresponding associated Mutables from sqlalchemy. BTW Mirantis has already implemented wrappers that fix the bug. It can be usefull https://github.com/openstack/fuel-web/blob/master/nailgun/nailgun/db/sqlalchemy/models/mutable.py

Responsible: zzzeek