De-structuring a list of maps based on given keys

destructure.groovy

def data = [
  [ user:'tim',  time:1, age:33, weight:90, height:2.2 ],
  [ user:'anne', time:2, height:1.8 ]
]

def destructure = { List<Map> listOfMaps, idFields=[], boolean allowNull=true ->
  [ idFields ].flatten().with { flatFields ->
    ( listOfMaps*.keySet().flatten() as Set ).with { names ->
      names = names - flatFields
      listOfMaps.inject( [] ) { list, map ->
        map.subMap( flatFields ).with { m ->
          list.addAll( names.findResults { name ->
            if( map[name] != null || allowNull ) {
              [ *:m, (name): map[name] ]
            }
          } )
          list
        }
      }
    }
  }
}

assert destructure( data ) == [ 
  [user:'tim'],
  [time:1],
  [age:33],
  [weight:90],
  [height:2.2],
  [user:'anne'],
  [time:2],
  [age:null],
  [weight:null],
  [height:1.8]
]

assert destructure( data, 'user' ) == [ 
  [user:'tim',  time:1],
  [user:'tim',  age:33],
  [user:'tim',  weight:90],
  [user:'tim',  height:2.2],
  [user:'anne', time:2],
  [user:'anne', age:null],
  [user:'anne', weight:null],
  [user:'anne', height:1.8]
]

assert destructure( data, [ 'user', 'time' ] ) == [ 
  [user:'tim',  time:1, age:33],
  [user:'tim',  time:1, weight:90],
  [user:'tim',  time:1, height:2.2],
  [user:'anne', time:2, age:null],
  [user:'anne', time:2, weight:null],
  [user:'anne', time:2, height:1.8]
]

assert destructure( data, [ 'user', 'time' ], false ) == [ 
  [user:'tim', time:1, age:33],
  [user:'tim', time:1, weight:90],
  [user:'tim', time:1, height:2.2],
  [user:'anne', time:2, height:1.8]
]