143 lines
4.5 KiB
Python
143 lines
4.5 KiB
Python
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# This file is part of Patsy
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# Copyright (C) 2011-2012 Nathaniel Smith <njs@pobox.com>
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# See file LICENSE.txt for license information.
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# The core 'origin' tracking system. This point of this is to have machinery
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# so if some object is ultimately derived from some portion of a string (e.g.,
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# a formula), then we can keep track of that, and use it to give proper error
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# messages.
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# These are made available in the patsy.* namespace
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__all__ = ["Origin"]
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class Origin(object):
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"""This represents the origin of some object in some string.
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For example, if we have an object ``x1_obj`` that was produced by parsing
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the ``x1`` in the formula ``"y ~ x1:x2"``, then we conventionally keep
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track of that relationship by doing::
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x1_obj.origin = Origin("y ~ x1:x2", 4, 6)
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Then later if we run into a problem, we can do::
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raise PatsyError("invalid factor", x1_obj)
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and we'll produce a nice error message like::
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PatsyError: invalid factor
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y ~ x1:x2
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^^
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Origins are compared by value, and hashable.
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"""
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def __init__(self, code, start, end):
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self.code = code
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self.start = start
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self.end = end
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@classmethod
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def combine(cls, origin_objs):
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"""Class method for combining a set of Origins into one large Origin
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that spans them.
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Example usage: if we wanted to represent the origin of the "x1:x2"
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term, we could do ``Origin.combine([x1_obj, x2_obj])``.
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Single argument is an iterable, and each element in the iterable
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should be either:
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* An Origin object
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* ``None``
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* An object that has a ``.origin`` attribute which fulfills the above
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criteria.
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Returns either an Origin object, or None.
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"""
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origins = []
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for obj in origin_objs:
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if obj is not None and not isinstance(obj, Origin):
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obj = obj.origin
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if obj is None:
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continue
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origins.append(obj)
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if not origins:
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return None
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codes = set([o.code for o in origins])
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assert len(codes) == 1
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start = min([o.start for o in origins])
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end = max([o.end for o in origins])
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return cls(codes.pop(), start, end)
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def relevant_code(self):
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"""Extracts and returns the span of the original code represented by
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this Origin. Example: ``x1``."""
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return self.code[self.start:self.end]
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def __eq__(self, other):
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return (isinstance(other, Origin)
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and self.code == other.code
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and self.start == other.start
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and self.end == other.end)
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def __ne__(self, other):
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return not self == other
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def __hash__(self):
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return hash((Origin, self.code, self.start, self.end))
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def caretize(self, indent=0):
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"""Produces a user-readable two line string indicating the origin of
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some code. Example::
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y ~ x1:x2
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^^
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If optional argument 'indent' is given, then both lines will be
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indented by this much. The returned string does not have a trailing
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newline.
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"""
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return ("%s%s\n%s%s%s"
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% (" " * indent,
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self.code,
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" " * indent,
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" " * self.start,
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"^" * (self.end - self.start)))
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def __repr__(self):
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return "<Origin %s->%s<-%s (%s-%s)>" % (
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self.code[:self.start],
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self.code[self.start:self.end],
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self.code[self.end:],
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self.start, self.end)
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# We reimplement patsy.util.no_pickling, to avoid circular import issues
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def __getstate__(self):
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raise NotImplementedError
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def test_Origin():
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o1 = Origin("012345", 2, 4)
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o2 = Origin("012345", 4, 5)
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assert o1.caretize() == "012345\n ^^"
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assert o2.caretize() == "012345\n ^"
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o3 = Origin.combine([o1, o2])
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assert o3.code == "012345"
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assert o3.start == 2
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assert o3.end == 5
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assert o3.caretize(indent=2) == " 012345\n ^^^"
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assert o3 == Origin("012345", 2, 5)
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class ObjWithOrigin(object):
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def __init__(self, origin=None):
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self.origin = origin
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o4 = Origin.combine([ObjWithOrigin(o1), ObjWithOrigin(), None])
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assert o4 == o1
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o5 = Origin.combine([ObjWithOrigin(o1), o2])
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assert o5 == o3
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assert Origin.combine([ObjWithOrigin(), ObjWithOrigin()]) is None
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from patsy.util import assert_no_pickling
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assert_no_pickling(Origin("", 0, 0))
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