Support in-place patch/revert

[mikaelho]

I request adding an in-place patch/revert capability, i.e. option for performing these operations without copying the target structure.

This would be a useful performance optimization in some large-volume use cases. I also have a functional need of patching in place while recording all changes made to the structure.

This could be implemented as an additional, optional parameter to patch and revert:

Patch:

def patch(diff_result, destination, in_place=False):
    """Docstring"""
    if not in_place:
      destination = copy.deepcopy(destination)

Revert:

def revert(diff_result, destination, in_place=False):
    """Docstring"""
    return patch(swap(diff_result), destination, in_place)

And tested with e.g.

a = {
  'a' : 1
}
b = {
  'a' : 2
}
changes = list(diff(a, b))

c = patch(changes, a)
assert a != c

d = revert(changes, c, in_place=True)
assert a == d
assert c == d

e = patch(changes, a, in_place=True)
assert a == e

[jirikuncar]

@mikaelho are you willing to send a pull-request with proposed tests?

[mikaelho]

Never done it before. I will try.

[jirikuncar]

@mikaelho don't worry 😉 Just have a look at some past commits to see how things are done. If you have any question just ping me.

[mikaelho]

Done - my first pull request ever.

#92