Signal a failing grade if mistakes are detected in the submitted code

fail_if_code_feedback() uses code_feedback() to detect if there are differences between the user's submitted code and the solution code (if available). If the exercise does not have an associated solution, or if there are no detected differences between the user's and the solution code, no grade is returned.

See graded() for more information on gradethis grade-signaling functions.

fail_if_code_feedback(
  message = NULL,
  user_code = .user_code,
  solution_code = .solution_code,
  ...,
  env = parent.frame(),
  hint = TRUE,
  encourage = getOption("gradethis.fail.encourage", FALSE),
  allow_partial_matching = getOption("gradethis.allow_partial_matching", TRUE)
)

Arguments

message	A character string of the message to be displayed. In all grading helper functions other than graded(), message is a template string that will be processed with glue::glue().
user_code	String containing user or solution code. For ease of use in grade_this(), .user_code or .solution_code are by default retrieved from the calling environment.
solution_code	String containing user or solution code. For ease of use in grade_this(), .user_code or .solution_code are by default retrieved from the calling environment.
...	Arguments passed on to graded correct A logical value of whether or not the checked code is correct. type The type and location of the feedback object provided to learnr. See https://rstudio.github.io/learnr/exercises.html#Custom_checking for more details.type may be one of "auto", "success", "info", "warning", "error", or "custom".location may be one of "append", "prepend", or "replace". location The type and location of the feedback object provided to learnr. See https://rstudio.github.io/learnr/exercises.html#Custom_checking for more details.type may be one of "auto", "success", "info", "warning", "error", or "custom".location may be one of "append", "prepend", or "replace".
env	Environment used to standardise formals of the user and solution code. Defaults to retrieving .envir_prep from the calling environment. If not found, the parent.frame() will be used.
hint	Include a code feedback hint with the failing message? This argument only applies to fail() and fail_if_equal() and the message is added using the default options of give_code_feedback() and maybe_code_feedback(). The default value of hint can be set using gradethis_setup() or the gradethis.fail.hint option.
encourage	Incude a random encouraging phrase with random_encouragement()? The default value of encourage can be set using gradethis_setup() or the gradethis.fail.encourage option.
allow_partial_matching	A logical. If FALSE, the partial matching of argument names is not allowed and e.g. runif(1, mi = 0) will return a message indicating that the full formal name min should be used. The default is set via the gradethis.allow_partial_matching option, or by gradethis_setup().

Value

Signals an incorrect grade with feedback if there are differences between the submitted user code and the solution code. If solution code is not available, no grade is returned.

See also

Other grading helper functions: graded(), pass(), fail(), pass_if(), fail_if(), pass_if_equal(), fail_if_equal().

Examples

# Suppose the exercise prompt is to generate 5 random numbers, sampled from
# a uniform distribution between 0 and 1. In this exercise, you know that
# you shouldn't have values outside of the range of 0 or 1, but you'll
# otherwise need to check the submitted code to know that the student has
# chosen the correct sampling function.

grader <-
# ```{r example-check}
  grade_this({
    fail_if(length(.result) != 5, "I expected 5 numbers.")
    fail_if(
      any(.result < 0 | .result > 1), 
      "I expected all numbers to be between 0 and 1."
    )
    
    # Specific checks passed, but now we want to check the code.
    fail_if_code_feedback()
    
    # All good!
    pass()
  })
# ```

.solution_code <- "
# ```{r example-check}
  runif(5)
# ```
"

# Not 5 numbers...
grader(mock_this_exercise(runif(1), !!.solution_code))
#> <gradethis_graded: [Incorrect] I expected 5 numbers.>

# Not within [0, 1]...
grader(mock_this_exercise(rnorm(5), !!.solution_code))
#> <gradethis_graded: [Incorrect]
#>   I expected all numbers to be between 0 and 1.
#> >

# Passes specific checks, but hard to tell so check the code...
grader(mock_this_exercise(runif(5, 0.25, 0.75), !!.solution_code))
#> <gradethis_graded: [Incorrect]
#>   In `runif(5, 0.25, 0.75)`, I expected `0` where you wrote `0.25`.
#> >
grader(mock_this_exercise(rbinom(5, 1, 0.5), !!.solution_code))
#> <gradethis_graded: [Incorrect]
#>   I expected you to call `runif()` where you called `rbinom()`.
#> >

# Perfect!
grader(mock_this_exercise(runif(n = 5), !!.solution_code))
#> <gradethis_graded: [Correct] Beautiful! Correct!>