Formatting the output of parse with a CASE is broken

[Alberto15Romero]

We have parsed a SQL with a CASE statement and when formatting the output of the parse function, the library throws an Exception.

We have opened a pull request with a test to prove it and a solution that might need some hinters to improve it.

How to replicate the issue:

$ python
>>> from moz_sql_parser import parse, format
>>> format(parse("SELECT age, CASE WHEN age < 13 THEN 'child' WHEN age < 20 THEN 'teenager' ELSE 'adult' END AS age_range FROM people"))
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/alberto/.local/lib/python3.6/site-packages/moz_sql_parser/__init__.py", line 59, in format
    return Formatter(**kwargs).format(json)
  File "/home/alberto/.local/lib/python3.6/site-packages/moz_sql_parser/formatting.py", line 153, in format
    return self.query(json)
  File "/home/alberto/.local/lib/python3.6/site-packages/moz_sql_parser/formatting.py", line 293, in query
    for clause in self.clauses
  File "/home/alberto/.local/lib/python3.6/site-packages/moz_sql_parser/formatting.py", line 294, in <genexpr>
    for part in [getattr(self, clause)(json)]
  File "/home/alberto/.local/lib/python3.6/site-packages/moz_sql_parser/formatting.py", line 300, in select
    return 'SELECT {0}'.format(self.dispatch(json['select']))
  File "/home/alberto/.local/lib/python3.6/site-packages/moz_sql_parser/formatting.py", line 157, in dispatch
    return self.delimited_list(json)
  File "/home/alberto/.local/lib/python3.6/site-packages/moz_sql_parser/formatting.py", line 177, in delimited_list
    return ', '.join(self.dispatch(element) for element in json)
  File "/home/alberto/.local/lib/python3.6/site-packages/moz_sql_parser/formatting.py", line 177, in <genexpr>
    return ', '.join(self.dispatch(element) for element in json)
  File "/home/alberto/.local/lib/python3.6/site-packages/moz_sql_parser/formatting.py", line 162, in dispatch
    return self.value(json)
  File "/home/alberto/.local/lib/python3.6/site-packages/moz_sql_parser/formatting.py", line 180, in value
    parts = [self.dispatch(json['value'])]
  File "/home/alberto/.local/lib/python3.6/site-packages/moz_sql_parser/formatting.py", line 170, in dispatch
    return self.op(json)
  File "/home/alberto/.local/lib/python3.6/site-packages/moz_sql_parser/formatting.py", line 199, in op
    return method(value)
  File "/home/alberto/.local/lib/python3.6/site-packages/moz_sql_parser/formatting.py", line 247, in _case
    parts.extend(['WHEN', self.dispatch(check['when'])])
KeyError: 'when'

Pull Request

#125

[klahnakoski]

This has been fixed since the new version