feat: carapace support

[ShalokShalom]

Carapace is an universal shell completion library and binary

Reference #262 (comment)

[TorchedSammy]

i tried this a while ago, but i couldn't really figure out a good way to use carapace. if someone else would like to work on it unofficially, please do!

[jdugan6240]

Ok, according to the linked issue, Carapace has the export command which basically does what we need. However, it outputs its completions in json format, not a simple newline-separated series of values. So, while doable, this would probably be best implemented as a plugin rather than a script that can be simply plugged into one's config.

I'll get going on that when I get the chance.

[TorchedSammy]

So, while doable, this would probably be best implemented as a plugin rather than a script that can be simply plugged into one's config.

seems plenty easy to do without a plugin. i even have a one liner to decode json in lua.

[jdugan6240]

I'd like to see this one liner, because I haven't found a way to parse json to a Lua table without a library (granted, it doesn't need to be a particularly fancy library).

Once you've got a Lua table representing the json, it's just constructing completion groups with the data.

[TorchedSammy]

load('return ' .. jsonstr:gsub('("[^"]-"):', '[%1]='))()

i don't remember where i got this from but i used it since i didn't want to get the rxi json library just for my image upload script (which, yes, is in lua)

[jdugan6240]

Unfortunately, that breaks when string values in the json table happen to contain a ":, as in the following example:

jsonstr = '{"test": "hello \\":"}'
obj = load('return ' .. jsonstr:gsub('("[^"]-"):', '[%1]='))()

The above example crashes because the resulting string that's passed to load isn't valid Lua. The rxi json library of course handles this just fine.

Is it likely that carapace completion output would feature this edge case? No, but it is definitely possible.

So, as clever as that one liner is, I don't think we can rely on it for a robust carapace script. Plus, json.decode(jsonstr) is a lot easier to understand at a glance.