infinite recursion when trying to access an uninitialized property with getter function

[rikivillalba]

When trying to access an uninitialized property that has a getter, a stack overflow occurs

library(S7)

someclass <- new_class("someclass", properties = list(
  action = new_property(
    class_character,
    getter = function(self) self@action,
    setter = function(self, value) {
      self@action <- toupper(value)
      self 
    },
    default = "some action"
  )
))

x <- someclass()
x@action

#> Error: evaluation nested too deeply: infinite recursion / options(expressions=)?

as soon as I set a value the code works. Is this behaviour ok?
default property value also does not help.

[hadley]

This seems like a bug to me.

[t-kalinowski]

One solution might be to stop filtering out dynamic properties from the constructor args. I.e., remove this line (and update tests to match)

S7/R/constructor.R

Line 51 in ffb8ca9

self_args <- self_args[vlapply(properties, function(x) is.null(x$getter))]

The object constructor would then have signature function(action = "some action").

This intersects with #376, where we are also discussing changing the object constructor signature.

[lawremi]

The current design of property getting is confusing to me. It seems to require that a property with a getter not use its underlying attribute value at all. The getter is run if and only if the attribute value is NULL.

I would prefer that instead we always run the getter, if present, and we use the same trick as property setting to avoid infinite recursion (as already proposed in the C code).