Additional properties support

[delvedor]

Added support for additionalProperties.
See discussion in #5.

Ps: I took the occasion to add a table of contents to the docs.

[mcollina]

We should add a case for additionalProperties: true and additionalProperties: false. If additionalProperties: true is passed, we use fast-safe-stringify to JSONify them (to avoid circular references).

[delvedor]

In case of additionalProperties: false all the values that are not present in properties/patternProperties are ignored.

Regarding additionalProperties: true, I never see in the json docs this case, only false or object. That's why I wrote this.

[mcollina]

Look at this: https://spacetelescope.github.io/understanding-json-schema/reference/object.html.

The additionalProperties keyword is used to control the handling of extra stuff, that is, properties whose names are not listed in the properties keyword. By default any additional properties are allowed.

I think we should "bend the rule here", and support additionalProperties  as being false by default. If someone wants to add random properties, I think we should support additionalProperties: true.

[delvedor]

For me is ok support additionalProperties: true, but how?
You say to use fast-safe-stringify, but we can't use require in the generated code.
I saw the source code of fast-safe-stringify and it's composed by three different functions and it's exposing only one of them, so I can't fast-safe-stringify.toString() as we do with the other functions.

Ideas?

[mcollina]

You can pass it in as an argument of https://github.com/mcollina/fast-json-stringify/blob/master/index.js#L55.

[delvedor]

If this implementation is ok for you I'll update the docs to describe this behaviour :)

[mcollina]

The implementation is ok.

[mcollina]

Does this slows down benchmarks? I don't think so, but please check.

Anyway, LGTM.

[delvedor]

I'll add more benchmarks in the future.
In the meantime I merge this :P