Snapshot error on Windows (encoding problem)

[maelle]

In this reprex package https://github.com/maelle/encoding.problem I have a test

test_that("multiplication works", {
  bla <- list(someone = "Maëlle")
  expect_snapshot_output(print(bla))
})

I created the snapshot on Ubuntu. On Windows the test fails https://github.com/maelle/encoding.problem/actions/runs/1845617963

With error

> test_check("encoding.problem")
Error in gsub("\n", paste0("\n", prefix), x, fixed = TRUE) : 
Error: Error: R CMD check found ERRORs
  input string 1 is invalid UTF-8
Calls: test_check ... vapply -> FUN -> paste0 -> indent_add -> paste0 -> gsub
Execution halted

Which comes from indent_add() and functions it calls.

[cderv]

I have also encountered this error after the last testthat release.

At the time, at wondered if it was related to using brio for reading and writing, so assuming UTF-8. (6666662)

There is a place in eval_with_output() where file is read assuming UTF-8 but not sure the file is UTF-8 on windows

testthat/R/capture-output.R

Lines 44 to 60 in 6666662

	eval_with_output <- function(code, print = FALSE, width = 80) {
	path <- withr::local_tempfile()
	if (!is.null(width)) {
	local_width(width)
	}
	result <- withr::with_output_sink(path, withVisible(code))
	if (result$visible && print) {
	withr::with_output_sink(path, testthat_print(result$value), append = TRUE)
	}
	list(
	val = result$value,
	vis = result$visible,
	out = brio::read_lines(path)
	)
	}

testthat:::eval_with_output(print("maëlle"))
#> $val
#> [1] "maëlle"
#> 
#> $vis
#> [1] FALSE
#> 
#> $out
#> [1] "[1] \"ma<eb>lle\""

With parent commit before brio switch

testthat::eval_with_output(print("maëlle"))
#> $val
#> [1] "maëlle"
#> 
#> $vis
#> [1] FALSE
#> 
#> $out
#> [1] "[1] \"maëlle\""

withr::with_output_sink() will let sink() write to a file. If the connection is not opened, it will probably opened a connection in native encoding and the resulting file cannot be read as UTF-8 using brio::read_lines(). This is the part that creates the "wrong" value.

I know sink() is source of issue with encoding (r-lib/evaluate#59) and file connection and encoding are not realy easy to master. So I don't know if this is something hat can be improve for windows users with snapshot test.

I just observe this

tmp <- tempfile()
sink(tmp)
print('ë')
sink()
brio::read_lines(tmp)
#> [1] "[1] \"\xeb\""
unlink(tmp)

tmp <- tempfile()
con <- file(tmp, encoding = "UTF-8")
sink(con)
print('ë')
sink()
brio::read_lines(tmp)
#> [1] "[1] \"ë\""
unlink(tmp)

Anyway, just sharing what I had found when stubbling into this issue as @maelle shared here Windows issue with me.
If possible, insuring to write as UTF-8 could help, or maybe not use brio::read_lines() in this specific place ?

Hope it helps.

[hadley]

Is this fixed in R4.2? If so, do you need it to work in R4.1 too? (It's likely to be a couple of hours work for me, so I'd prefer to use that time on other things if your motivating issue is resolved by updating R).

[maelle]

Indeed it now works https://github.com/maelle/encoding.problem/actions/runs/3103119734
We can definitely work without a fix 🙂

[hadley]

I fixed this anyway, thanks to @cderv's analysis and a hint from Kurt Hornik.