parse_version() should accept None and empty strings

[pombredanne]

In https://github.com/nexB/univers/blob/63bd5aec16ec95b5b811ede638ac225f3ab1f6c6/src/univers/versions.py#L286
we should let parse_version() accept None and empty strings, otherwise the calling code has too much work to do.

[Hritik14]

@pombredanne
In the current structure this should translate to the build_value fn:
https://github.com/nexB/univers/blob/a52ea9900d87ef6cd0ed989bf20a41a794cf39c4/src/univers/versions.py#L87

Also, now that we have is_valid, is this even required ?
https://github.com/nexB/univers/blob/a52ea9900d87ef6cd0ed989bf20a41a794cf39c4/src/univers/versions.py#L70

[Hritik14]

To add,
Version(None) throws error

[Subhraneel77]

Adding version("") should work , as assigning "" to a variable to initialize an empty string in Python.
@pombredanne

[Hritik14]

Version(None) still throws an error.

>>> from univers.versions import Version
>>> Version(None)
---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
<ipython-input-2-dece84ce917a> in <module>
----> 1 Version(None)

~/Contrib/univers/src/univers/versions.py in __init__(self, string, normalized_string, value)
      5     _inst_dict['normalized_string'] = normalized_string
      6     _inst_dict['value'] = value
----> 7     self.__attrs_post_init__()

~/Contrib/univers/src/univers/versions.py in __attrs_post_init__(self)
     59
     60     def __attrs_post_init__(self):
---> 61         normalized_string = self.normalize(self.string)
     62         if not self.is_valid(normalized_string):
     63             raise InvalidVersion(f"{self.string!r} is not a valid {self.__class__!r}")

~/Contrib/univers/src/univers/versions.py in normalize(cls, string)
     86         """
     87         # FIXME: Is removing spaces and strip v the right thing to do?
---> 88         return remove_spaces(string).rstrip("v")
     89
     90     @classmethod

~/Contrib/univers/src/univers/utils.py in remove_spaces(string)
      7
      8 def remove_spaces(string):
----> 9     return "".join(string.split())
     10
     11

AttributeError: 'NoneType' object has no attribute 'split'

[pombredanne]

Version(None) still throws an error.

IMHO that's a feature. When would a None version make sense?

[pombredanne]

Adding version("") should work , as assigning "" to a variable to initialize an empty string in Python. @pombredanne

Thanks, but None or empty would be the same... and I am not sure this would make any sense.

[Hritik14]

@pombredanne

When would a None version make sense?

Please see #33

[janniclas]

This causes problems in vulnerablecode when the importers/improvers get incomplete data as it is currently the case for some of them. This should be handled in the calling code in vulnerablecode ( PR aboutcode-org/vulnerablecode#1215 ).
However, I think we could also make a case for handling this in this lib, as this crash came rather unexpected to be honest.

[pombredanne]

@janniclas Thanks!
Now, what should we return in these cases? None?