Fix AlertCondition backwards compatibility

[ali-essam]

What does this do?

Add useNewAlerts property to AlertCondition and default it to False

Why is it a good idea?

When AlertCondition is used inside of Alert.alertConditions, json serialization fails as the property is not set. When the default is set to False this will allow the AlertCondition to behave as expected when used with old grafana alerting. In case of 8.x and 9.x, this is already overriden to True in the code so the functionality will work as expected in the new alerting.

In [14]: from grafanalib import core as G

In [15]: from grafanalib import _gen as glGen

In [16]: import json

In [17]: json.dumps(G.Alert(name='name', message='message', alertConditions=[G.AlertCondition(G.Target(refI
    ...: d="A"), G.Evaluator('a', 'b'), G.TimeRange('5', '6'), 'd', 'e')]), cls=glGen.DashboardEncoder)
---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
<ipython-input-17-a458c89b5490> in <module>
----> 1 json.dumps(G.Alert(name='name', message='message', alertConditions=[G.AlertCondition(G.Target(refId="A"), G.Evaluator('a', 'b'), G.TimeRange('5', '6'), 'd', 'e')]), cls=glGen.DashboardEncoder)

~/.pyenv/versions/3.8.13/lib/python3.8/json/__init__.py in dumps(obj, skipkeys, ensure_ascii, check_circular, allow_nan, cls, indent, separators, default, sort_keys, **kw)
    232     if cls is None:
    233         cls = JSONEncoder
--> 234     return cls(
    235         skipkeys=skipkeys, ensure_ascii=ensure_ascii,
    236         check_circular=check_circular, allow_nan=allow_nan, indent=indent,

~/.pyenv/versions/3.8.13/lib/python3.8/json/encoder.py in encode(self, o)
    197         # exceptions aren't as detailed.  The list call should be roughly
    198         # equivalent to the PySequence_Fast that ''.join() would do.
--> 199         chunks = self.iterencode(o, _one_shot=True)
    200         if not isinstance(chunks, (list, tuple)):
    201             chunks = list(chunks)

~/.pyenv/versions/3.8.13/lib/python3.8/json/encoder.py in iterencode(self, o, _one_shot)
    255                 self.key_separator, self.item_separator, self.sort_keys,
    256                 self.skipkeys, _one_shot)
--> 257         return _iterencode(o, 0)
    258
    259 def _make_iterencode(markers, _default, _encoder, _indent, _floatstr,

~/....venv/lib/python3.8/site-packages/grafanalib/_gen.py in default(self, obj)
     21         to_json_data = getattr(obj, 'to_json_data', None)
     22         if to_json_data:
---> 23             return to_json_data()
     24         return json.JSONEncoder.default(self, obj)
     25

~/.../.venv/lib/python3.8/site-packages/grafanalib/core.py in to_json_data(self)
   1203             'query': {
   1204                 'model': self.target.to_json_data(),
-> 1205                 'params': self.__get_query_params(),
   1206             },
   1207             'reducer': {

~/.../.venv/lib/python3.8/site-packages/grafanalib/core.py in __get_query_params(self)
   1190     def __get_query_params(self):
   1191         # Grafana 8.x alerts do not put the time range in the query params.
-> 1192         if self.useNewAlerts:
   1193             return [self.target.refId]
   1194

AttributeError: 'AlertCondition' object has no attribute 'useNewAlerts'

Context

Fixes #545

Questions

• Is defaulting to False a safe assumption?

[ali-essam]

@JamesGibo can you please review this 🙏 ?