{ "ls -R":
  { "target_fields": ["tree", "direct"]
  , "expression":
    { "type": "let*"
    , "bindings":
      [ [ "tree"
        , { "type": "TREE"
          , "$1":
            { "type": "map_union"
            , "$1":
              { "type": "foreach"
              , "var": "dep"
              , "range": {"type": "FIELD", "name": "tree"}
              , "body":
                {"type": "DEP_RUNFILES", "dep": {"type": "var", "name": "dep"}}
              }
            }
          }
        ]
      , [ "direct"
        , { "type": "map_union"
          , "$1":
            { "type": "foreach"
            , "var": "dep"
            , "range": {"type": "FIELD", "name": "direct"}
            , "body":
              {"type": "DEP_RUNFILES", "dep": {"type": "var", "name": "dep"}}
            }
          }
        ]
      , [ "inputs"
        , { "type": "map_union"
          , "$1":
            [ { "type": "singleton_map"
              , "key": "tree"
              , "value": {"type": "var", "name": "tree"}
              }
            , {"type": "var", "name": "direct"}
            ]
          }
        ]
      ]
    , "body":
      { "type": "RESULT"
      , "artifacts":
        { "type": "ACTION"
        , "outs": ["_out"]
        , "inputs": {"type": "var", "name": "inputs"}
        , "cmd": ["sh", "-c", "find . -name '*.txt' > _out"]
        }
      }
    }
  }
}