How to get a list of all Wikidata properties?

Using action=wbsearchentities with type=property should do. Wikidata API doc is here, search for "=wb" to get the Wikidata-specific functions.

Update: thank to @nerab's answer, I updated wikidata-properties-dumper to use Quarry SQL results: that's indead much cleaner :)

Update 2: Quarry wasn't that flexible, I moved to use a SPARQL query and wrapped that in a Wikidata CLI command: wd props

I wrote a small script to query all properties with wikidata API's action=wbgetentities. It generate a json file with

key: value

being

property Pid: property label in the request language

I published the outputs for a few languages and could do for other language on request until there is an official (and cleaner) answer for this need

Thanks to the comments in @maxlath's project, I found Quarry.

A list of all Wikidata properties can be fetched from

http://quarry.wmflabs.org/run/45013/output/1/json

This particular list is in English, but the query can be modified for other languages, too.