In for loop tryCatch of render, can warnings be logged outside the document without a return in the document?

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I am playing around with Rmarkdown and assertthat to produce a number of .pdf files in a loop. Each has a assert chunk, with the option set to include=FALSE.

I have a file to deliberately succeed with this chunk:

assert_that(are_equal(length(cars), length(cars)), msg = "Wrong length")

And a file to deliberately error with this chunk:

assert_that(are_equal(length(cars), 1), msg = "Wrong length")

I also have a file that I am trying to generate a warning from, with this chunk:

validate_that(are_equal(length(cars), 1), msg = "Wrong length")

I loop through these in this way:

library(loggr)

log_file("./assert_test.log")

files <- c("./success.Rmd", "./warn.Rmd", "./error.Rmd")

for(this_file in files){
  tryCatch(
    rmarkdown::render(
      input = this_file,
      output_file = paste0(this_file, ".pdf")
    ),
    error = function(cond) {
      log_info(paste("Error for:", this_file))
      log_info("Here's the original error message: ")
      log_info(cond)
      return(NA)
    },
    warning = function(cond) {
      log_info(paste("Warning for:", this_file))
      log_info("Here's the original warning message: ")
      log_info(cond)
      return(NULL)
    },
    finally = {
      log_info(paste("Finish processing for:", this_file))
    }
  )
}
  1. The success.Rmd correctly produces an output, the assert chunk is not visible in the output, and does not print it's return.
  2. The error.Rmd (also correctly) does not produce an output, but does produce an error message, which is captured in assert_test.log.
  3. I would like the warn.Rmd to generate a .pdf, with the output not showing any evidence that the assert chunk is present (no code or return in the document), but also to pass the warning up to the file assert_test.log for capture. Right now the option include=FALSE does not give any warning in the output, or the log.

Is this possible? If it isn't is it because I have fundamentally misunderstood how I should be approaching this goal?