Use envir_prep for exercise checking

DESCRIPTION

@@ -41,3 +41,4 @@ Authors@R: c(
     )
 RoxygenNote: 6.1.1
 VignetteBuilder: knitr
+Encoding: UTF-8

R/test-exercise.R

@@ -76,12 +76,16 @@ test_exercise <- function(sct,
 #' Run SCT until it fails
 #'
 #' @param code the SCT script to run as an expression
+#' @param envir environment in which to execute the SCT script
 #'
 #' @export
-run_until_fail <- function(code) {
+run_until_fail <- function(code, envir = NULL) {
   tryCatch({
+    if (is.null(envir)) {
+      envir <- tw$get("state")$get("test_env")
+    }
     # Run the SCT
-    eval(code, envir = tw$get("state")$get("test_env"))
+    eval(code, envir = envir)
     # If it got here, the SCT passed
     return(list(correct = TRUE, message = tw$get("success_msg")))
   }, sct_failure = function(e) {

R/utils-learnr.R

@@ -21,6 +21,7 @@
 #' @param envir_result 	The R environment after the execution of the chunk.
 #' @param evaluate_result The return value from the \code{evaluate::evaluate}
 #'   function.
+#' @param envir_prep A copy of the R environment before the execution of the exercise
 #' @param ... Unused (include for compatibility with parameters to be added in
 #'   the future)
 #'
@@ -33,9 +34,10 @@ testwhat_learnr <- function(label = NULL,
                             check_code = NULL,
                             envir_result = NULL,
                             evaluate_result = NULL,
+                            envir_prep = NULL,
                             ...) {
-  
-  ######### START COPY FROM grade_learnr ##################
+
+  ######### START COPY FROM gradethis ##################
   # Sometimes no user code is provided, but
   # that means there is nothing to check. Also,
   # you do not want to parse NULL
@@ -47,7 +49,7 @@ testwhat_learnr <- function(label = NULL,
       location = "append"
     ))
   }
-  
+
   # Sometimes no solution is provided, but that
   # means there is nothing to check against. Also,
   # you do not want to parse NULL
@@ -59,15 +61,15 @@ testwhat_learnr <- function(label = NULL,
       location = "append"
     ))
   }
-  ######### END COPY FROM grade_learnr ##################
-  
+  ######### END COPY FROM gradethis ##################
+
   setup_state(sol_code = solution_code,
               stu_code = user_code,
               sol_env = NULL,
               stu_env = envir_result,
               stu_result = evaluate_result)
-  
-  res <- run_until_fail(parse(text = check_code))
+
+  res <- run_until_fail(parse(text = check_code), envir = envir_prep)
   return(list(message = res$message,
               correct = res$correct,
               location = "append",