Calling interface choices in Script fails via JSON API

[bame-da]

See https://discuss.daml.com/t/exercise-interface-choice-on-daml-script-with-json-api/7134.

Repro:

Script:

module Main where

import Daml.Script
import DA.Foldable (mapA_)

data VFoo = VFoo with
  deriving (Eq, Show)

interface IFoo where
  viewtype VFoo

  c : Party

  choice Bar : ()
    controller (c this)
    do return ()

template Foo
  with
    p : Party
  where
    signatory p

    interface instance IFoo for Foo where
      view = VFoo
      c = p

test_foo p = do
  submit p do createCmd Foo with ..
  (cidList, _) <- unzip <$> queryInterface @IFoo p
  mapA_ (\ cid -> submit p do exerciseCmd cid Bar) cidList

Script call:

daml script --dar .daml/dist/repro-0.0.1.dar --ledger-host http://localhost --ledger-port 7575 --json-api --script-name Main:test_foo --access-token-file token --input-file input.json

Decoded token:

{
   "https://daml.com/ledger-api": {
     "ledgerId": "sandbox",
     "participantId": "sandbox",
     "applicationId": "script",
     "admin": true,
     "actAs": ["sandbox::122022077a14b5f6d5b324727c5aabc2123c88c75f0e455811992f4ad5f81735e887"],
     "readAs": []
   }
}

input.json:

"sandbox::122022077a14b5f6d5b324727c5aabc2123c88c75f0e455811992f4ad5f81735e887"

Replace the participant Id as appropriate.

[basvangijzel-DA]

Assess how much work this will be. If it's more than a day, I would say to push back as this will be removed for 3.x anyway.

[samuel-williams-da]

I think this could be done in a day. Would this need backporting to 2.8?