I use a class to write easily json when having generator.
```python
class StreamArray(list):
    def __init__(self, generator):
        super().__init__()
        self.generator = generator
    def __iter__(self):
        return self.generator
    def __len__(self):
        return 1
```
Below a test comparing json.dump and json.dumps.
```
>>> import json
>>> class StreamArray(list):
...     def __init__(self, generator):
...         super().__init__()
...         self.generator = generator
...     def __iter__(self):
...         return self.generator
...     def __len__(self):
...         return 1
... 
>>> g = (i for i in range(0))
>>> json.dumps({"a": StreamArray(g)})
'{"a": []}'
>>> f = open("/tmp/test.json", "w+")
>>> g = (i for i in range(0))
>>> json.dump({"a": StreamArray(g)}, f)
>>> f.close()
>>> print(open("/tmp/test.json").read())
{"a": ]}
```
I don't know if it's me or if there is actually a problem, could you help me ?