Checker API to accept the full result object.

[flpvsk]

Sometimes it's valuable for the checker to have other information about
the result under question, such as original sentences or their
attributes.

This commit changes the API of the checker to support that usecase. It'a
a breaking change, that can be avoided by extending the existent API
rather than replacing it.

Alternative proposal would be to add a different option to Markov
constructor options e.g. resultChecker: (result) => Boolean.

[coveralls]

Coverage increased (+0.09%) to 98.837% when pulling a189e93 on flpvsk:checker-upgrade into e75afce on scambier:master.

[flpvsk]

This is not a ready-to-merge PR. There are still more tests and changes to the documentation needed. If in general the idea is ok – I can to do those as well.

[scambier]

Thanks for your PR. Do you have a concrete usecase example where this change can be helpful?

[flpvsk]

Yes. In a side-project I'm using checker to discard results that were using only one source of text (as opposed to using several different sources). The source of text is set in an attribute of data sentences, so I need access to that info in the checker.

[flpvsk]

Also it seems like at some point the proposed API was the intended one, judging by this test (in the master branch):

https://github.com/scambier/markov-strings/blob/master/test/test.js#L117

[scambier]

Indeed, I totally forgot about that test. I'm ok with this PR, but it needs to be correctly implemented.

IMO, the "cleanest" solution would be to keep the checker(sentence) option but remove it from the docs & mark it deprecated, and add a new callback(result) (or whatever its name) that will be documented. This way, we don't break the API for existing users, and don't confuse new users with two virtually identical options or an ugly boolean switch. What do you think?

[flpvsk]

Ok, I agree that it's better to deprecate checker and add a new option. I wouldn't call the new option callback, because the word is usually associated with async APIs.filter?

[scambier]

Let's go with filter. I'll review and accept your PR once the code and tests are done, thanks :)

[flpvsk]

I've changed the implementation and the docs, added tests. Let me know if I missed something, otherwise it's ready to be merged.

[scambier]

Merged and published :)