Following the backend MR haskell-gargantext!261 (merged) , we have now removed the All data constructor from the Lang type, and we should do the same on the frontend code, to avoid impedance mismatches.

In practice, however, I don't think the frontend is ever sending to the backend corpus search where the lang is All : from my empirical tests I have seen that by default the frontend will send EN as a language if the user didn't specify a preference or if the search API provider doesn't support searching in other languages rather than english.