Q objects lack a useful repr

[Keryn Knight <django@…>]

>>> from django.db.models.query_utils import Q
>>> a = Q()
>>> b = Q(a=1, b=2)
>>> c = b & Q(c=3)
>>> d = c | Q(d=4)
>>> e = Q(d) & Q(e=5)
>>> f = e | ~Q(f=6)
>>> repr(f)  # actually just typing f<enter> into ipython/pdb/python REPL
'<django.db.models.query_utils.Q at 0x103184050>'

That's not exactly useful, given a Q object may represent a complex tree. As it turns out, Q objects do implement str, which is the SQL output for the Node subclass, which would be more useful than the above repr, and possibly more useful than the nested repr of .children

The simplest repr implementation would probably be something like:

def __repr__(self):
    return '{obj.__class__!r} {obj!s}'.format(obj=self)

[mardini]

PR: ​https://github.com/django/django/pull/2628

[Tim Graham <timograham@…>]

In 393ddc10a78354b573b9e746247df013f7bd6151:

Fixed #22531 -- Added tree.Node.repr and tests for the class.

While Node class has a useful __str__, its __repr__ is not that
useful. Added a __repr__ that makes use of the current __str__.
This is especially useful since the more popular Q class inherits
tree.Node. Also created new tests that cover most of Node class
functionality.