Lists disappear from typescript docs

[edsko]

If I have

data RequestSessionUpdate =
    RequestUpdateSourceFileFromFile RequestFilePath
  | RequestUpdateGhcOpts RequestGhcOption

with corresponding grammar

instance Json RequestSessionUpdate where
  grammar = label "SessionUpdate" $
    object $ mconcat [
          property "sessionUpdate" "updateSourceFileFromFile"
        . fromPrism requestUpdateSourceFileFromFile . prop "filePath"
      ,   property "sessionUpdate" "updateGhcOpts"
        . fromPrism requestUpdateGhcOpts . prop "options"
      ]

the documentation looks like

interface SessionUpdate {filePath ? : FilePath ;sessionUpdate ? : string ;options ? : GhcOption ;}

This is not ideal (see #5), but at least it lists all fields. However, once I change the type to use a list

data RequestSessionUpdate =
    RequestUpdateSourceFileFromFile RequestFilePath
  | RequestUpdateGhcOpts [RequestGhcOption]

the documentation suddenly doesn't list the options field at all anymore:

interface SessionUpdate {filePath ? : FilePath ;sessionUpdate ? : string ;}