vectors with same attributes incompatible

[monkeywithacupcake]

I don't understand why I get an error from vctrs::vec_ptype2() when comparing the type of two vectors with the same formatting. When they are created in the same way, how can they not be compatible.

library(formattable)
library(vctrs)
curr1 = formattable::currency(1:5)
curr2 = formattable::currency(6:10)

vctrs::vec_ptype2(curr1,curr2)

# Error:
# ! Can't combine `curr1` <formattable> and `curr2` <formattable>.
# ✖ Some attributes are incompatible.
# ℹ The author of the class should implement vctrs methods.
# ℹ See <https://vctrs.r-lib.org/reference/faq-error-incompatible-attributes.html>.
# Run `rlang::last_error()` to see where the error occurred.
# --- 
# Backtrace:
#      ▆
#    1. └─vctrs::vec_ptype2(curr1, curr2)
#  2.   └─vctrs (local) `<fn>`()
#  3.     └─vctrs::vec_default_ptype2(...)
#  4.       └─vctrs::stop_incompatible_type(...)
#  5.         └─vctrs:::stop_incompatible(...)
#  6.           └─vctrs:::stop_vctrs(...)
#  7.             └─rlang::abort(message, class = c(class, "vctrs_error"), ..., call = vctrs_error_call(call))

Inspired from formattable issue

[lionel-]

We have a same-type fallback that kicks in when all attributes are the same, but in this case I see that this attribute contains a function with a varying environment:

$formattable$postproc
function (str, x) 
sprintf("%s%s%s", ifelse(is.na(x), "", symbol), sep, str)
<bytecode: 0x11ca8b0b0>
<environment: 0x1299122d8>

You can fix this by implementing identity self-to-self ptype2 and cast methods. Implementing these methods is a good idea in general because it's also be a bit faster than the fallback paths.

See https://vctrs.r-lib.org/reference/howto-faq-coercion.html for more information.

[monkeywithacupcake]

I appreciate this comment. I am trying to follow those FAQ to modify the formattable package, but I am not understanding.

I modified my local copy of the formattable package to have

#' @importFrom vctrs vec_ptype2 vec_cast
NULL
#' @export
vec_ptype2.num_currency.num_currency <- function(x, y, ...) {
  x
}

#' @export
vec_cast.num_currency.num_currency  <- function(x, to, ...) {
  x
}

But, after I load_all() and attempt again, I still get the same error.

> curr1 <- num_currency(1:5)
> curr2 <- num_currency(6:10)
> 
> vec_ptype2(curr1,curr2)
Error:
! Can't combine `curr1` <formattable> and `curr2` <formattable>.
✖ Some attributes are incompatible.
ℹ The author of the class should implement vctrs methods.
ℹ See <https://vctrs.r-lib.org/reference/faq-error-incompatible-attributes.html>.
Run `rlang::last_error()` to see where the error occurred.

Likely a continuation of my lack of understanding, but I also tried the following (it also did not work):

#' @importFrom vctrs vec_ptype2 vec_cast
NULL
#' @export
vec_ptype2.formattable.formattable <- function(x, y, ...) {
  x
}

#' @export
vec_cast.formattable.formattable <- function(x, to, ...) {
  x
}

interestingly enough, I can build vectors

vctrs::vec_c(currency(1:3),currency(2:4))
# [1] $1.00 $2.00 $3.00 $2.00 $3.00 $4.00

[lionel-]

Did you redocument before loading-all?

[monkeywithacupcake]

Thank you for helping me through this. It works now. I can run over the conceptual implications with folks on the formattable package.