Don't modify passed options

[moll]

Themis modifies the passed-in options object. That causes unexpected stuff when that object is shared between invocations. E.g. when given immutable options:

TypeError: Can't add property file, object is not extensible
  at Object.Utils.defaults (/Users/user/node_modules/themis/src/themis.js:123:50)

[kumarharsh]

This is an expected behaviour, and follows the convention. If you want to maintain the object, pass it as a copy to themis.
See lodash#_.defaults

[moll]

Which convention? Modifying passed in objects unless they're clearly defined as output variables is a cardinal sin everywhere, regardless of language. Any random book on good API design talks about that. ;-)

[atrniv]

@kumarharsh means the convention for applying defaults is followed, however I think @moll has a point.
You don't expect your options object to be modified.

@moll I agree, there wasn't enough thought put in during the design phase while writing the initial code. Themis has largely been used as an internal tool and I've not had the time to make and document improvements in the last few months. However I'm currently working on a new version of themis which will have a much cleaner code base and one that will not mutate schema or options objects. Object mutations will occur only if you allow Themis to apply defaults.

In the meanwhile if you could open a pull request to fix this issue I would be happy to merge it.
I believe one possible solution is writing a Utils.extend function and using that to extend a defaults object with the passed in options.

[kumarharsh]

@moll I meant to say that it was in line with what other popular libraries, like lodash, have been doing.