Del Operation does not appear to be testing for the presence of its Value about aeson-diff

[thsutton]

The changeValue on Del is present (now) for the sake of computing the change metric used to minimise patches during construction. I should have defined a datatype to represent patches independently from the internal data structure.

In the near future I'll be making a major release which changes aeson-diff to use the RFC 6902 JSON Patch format. JSON Patch does not include a value on the remove operation but instead has a separate test operation which, used together, allows a similar semantics to the traditional behaviour you were expecting.

[thsutton]

@srijs I've just merged a branch preparing for a 1.0 release. This replaces the original ad hoc operations and patch format with the operations and JSON encoding defined in RFC 6902.

The Rem operation still has the non-operational Value (I may change this before cutting a release) but the semantics you want can now be implemented as described in the RFC using a Tst immediately succeeded by a Rem operation :

-- | Delete a 
del :: Pointer -> Value -> Patch
del p v = Patch [ Tst p v, Rem p v ]