API design question around getting low, high, (low+high) entropy values

[miketaylr]

Some feedback we got from @mikewest, in a blink-dev I2P:

Including low-entropy hints along with high-entropy hints in UADataValues seems like a reasonable thing to do, giving developers a clear way of requesting "UA Stuff", which seems like the way folks would be expected to use getHighEntropyValues(). There's something of a question there around API design (should we have a getAllValues() instead? Or a getJustLowEntropyValues()?) that seems like it would benefit from broader circulation.

The rationale for returning low-entropy hints along with high-entropy hints from getHighEntropyValues() is captured in #222 (comment), but essentially, if values change from high to low, we risk breaking deployed code.

Currently we have getHighEntropyValues(), and if you want low-entropy values, you'll have to grab those off of the NavigatorUAData interface directly.

There's a few scenarios where what Mike is proposing may be useful, and probably more that I'm not thinking about:

1. you want all the data (this assumes the UA is willing to give it to you), in a single API call
2. a hint has somehow transitioned from high to low entropy, or from low to high (we have half a solution for this)
3. you want a promise-y API to collect all the low entropy hints (otherwise you have to iterate over NavigatorUAData yourself and return your own promise)

I'm curious if other folks have thoughts here. @erik-anderson @amtunlimited @rowan-m @othermaciej

(This may also be an area where it's useful for some developers to get more familiar with the API so they can comment on ergonomics).

[rowan-m]

1. you want all the data (this assumes the UA is willing to give it to you), in a single API call

I'm trying to think of a use case for this beyond wanting to get a signature / fingerprint. As in, a call like this would presumably return any new hints that got added in the future. If I need that information for something functional, I should be explicitly requesting the token.

Something like option 3 seems kind of nice to me. Leave the default low-entropy values available as simple attributes so I don't need to mess around with a Promise, but likewise give me a general getValues() or similar that will accept all valid tokens. e.g.

navigator.userAgentData
.getValues(["architecture", "mobile"])
.then(ua => { console.log(ua) });
{
  "architecture": "x86",
  "mobile": false
}

[amtunlimited]

Yeah, I like the ergo of having everything in one function if you need to do something Promise-y anyways. My worry is trying to turn a low entropy hint back into a high one.

I'd almost be tempted to get rid of the non-Promise getters and say promises for everything if it wasn't so insanely disruptive to switch to async