tree 4eafcf2c12800217e0366ea1db1fd7e8aa918af1
parent 3fe02156777c9eff14a88826cf3aa495b5db3544
author Joe Tsai <joetsai@digital-static.net> 1501781709 -0700
committer GitHub <noreply@github.com> 1501781709 -0700

Refactor option evaluation logic (#32)

The previous implementation of options had a single "option" type
that was used to represent either an Ignore, Comparer, or Transformer
and all of the filters relevant to each of them.

We refactor this logic by creating a new type to represent each of
the fundamental options and filtering options. Construction of
filtered options is now as simple as wrapping the input option with
the appropriate filter type.

Evaluation of filters now takes a top-down two-step approach where
1. We start with the set of all options, and recursively apply the filters
to create the "applicable" set S.
2. We apply the set S.

Both steps are represented as the filter and apply methods on
each of the core options.

This approach has the following advantages:
* It is faster because the same filter that was applied to multiple
options now only needs to execute once.
* It more closely matches the documented algorithm in cmp.Equal.
* It allows for easier extension of the API to add new fundamental
option types.