Updates the mongo-style raw encoding to match v2 of the Extended JSON spec

[atheriel]

The $binary format has changed as of May 2017 (see commit). Before, we had

{"x" : {"$binary" : "//8=", "$type" : "00"}}

and now we have

{"x" : { "$binary" : {"base64" : "//8=", "subType" : "00"}}}

This commit should implement the new format. I believe this may be a breaking change for some users, but since they are likely interacting with MongoDB in some way they'll have to change at some point anyway.

[jeroen]

Looking at the reference manual it still describes the current format:

[atheriel]

Well, I didn't expect that.

[codecov-io]

Codecov Report

Merging #247 into master will not change coverage.
The diff coverage is 0%.

@@           Coverage Diff           @@
##           master     #247   +/-   ##
=======================================
  Coverage   63.82%   63.82%           
=======================================
  Files          88       88           
  Lines        2764     2764           
=======================================
  Hits         1764     1764           
  Misses       1000     1000

Impacted Files	Coverage Δ
R/asJSON.raw.R	57.14% <0%> (ø)	⬆️

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[atheriel]

The Q&A section of the spec suggests that implementations could support both (it terms the older version "Legacy"). Perhaps we could have a raw = "mongo2" option?

[jeroen]

Why do you need this new format? I would much prefer to stick with the mongo default behavior.

[jeroen]

I am running mongodb 4.0 and get this:

m <- mongolite::mongo()
m$insert(list(foo=charToRaw('bar')))
m$export()

{ "_id" : { "$oid" : "5b62271647a302483976d756" }, "foo" : { "$binary" : "YmFy", "$type" : "05" } }

So if neither the documentation nor the implementation of mongodb has changed, I don't think jsonlite should either.

[atheriel]

I don't need it -- and certainly don't mind holding off on changing it. I only noticed the issue when I tried to run the mongolite spec test suite.

As for your example, I noticed that export() eventually calls down into libbson's bson_as_json() function, which the inline API documentation refers to as returning "libbson's legacy JSON format". I think if it used bson_as_canonical_extended_json() it would return the expected string, if I'm reading the sources correctly. Maybe that's an issue to deal with in mongolite, though -- I'd be happy to submit something coordinated with this change to jsonlite.

Finally, there appears to be an open issue to update the mongodb docs, which clears up some of the mystery.

[jeroen]

OK thanks for the clarification. I think I should first aks clarification from the mongo devs if I should be switching to bson_as_canonical_extended_json() in mongolite, before merging the change here.

[atheriel]

Sounds reasonable to me!