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9269 :: why does JS backend return array with object?

• Niminem (orginal) [2022-06-28T02:04:55+02:00] view original

  Hi guys,

  I'm wrapping some of Google's Apps Script (targets the js backend):

  type
      SpreadsheetAppObj* = object
      Spreadsheet* = object
      Sheet* = object
  
  var SpreadsheetApp* {.importcpp, nodecl.}: SpreadsheetAppObj
  
  {.push importcpp.}
  proc getActiveSpreadsheet*(ssapp: SpreadsheetAppObj): Spreadsheet
  proc getActiveSheet*(ssapp: SpreadsheetAppObj): Sheet
  {.pop.}
  Run

  for var x = SpreadsheetApp.getActiveSpreadsheet, which returns a Spreadsheet object, why does Nim produce an array with the object inside: var x_452984848 = [SpreadsheetApp.getActiveSpreadsheet()]; ?

  Why not just return the object itself?

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• Niminem (orginal) [2022-06-28T02:09:42+02:00] view original

  I've played around with the importcpp pragma and converting ref object to object to no success. I've wrapped a js library before many months ago and remember it generating code with just the object being returned. Idk beats me

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• Yardanico (orginal) [2022-06-28T04:18:52+02:00] view original

  I think this is intended behaviour as Nim correctly uses the first value out of the array when you use the actual value. Maybe it's something to do with undefined, I'm not sure.

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• Araq (orginal) [2022-06-28T07:59:41+02:00] view original

  The usage of arrays in this context is to emulate pointers and the codegen sometimes needs pointers so that Nim's semantics can work. Consider:

  proc mutate(x: var int) = x = 4
  var global: int
  mutate(global)
  Run

  The code generator sometimes does this where it would not be required but it's hard to do better and to ensure correctness at the same time.

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