Allow feedback on unparsable unicode characters to render without `i1…

…8next` (#765)

* fix(unparsable_unicode_message): pre-interpolate message so feedback is comprehensible when `i18next` is unavailable

* docs: update NEWS

* docs: update documentation

* refactor(unparsable_unicode_message): use `sub()` rather than `glue()` to handle interpolation

DESCRIPTION

@@ -72,5 +72,5 @@ Config/Needs/coverage: covr
 Config/Needs/website: pkgdown, tidyverse/tidytemplate
 Encoding: UTF-8
 Roxygen: list(markdown = TRUE)
-RoxygenNote: 7.2.1
+RoxygenNote: 7.2.3
 SystemRequirements: pandoc (>= 1.14) - http://pandoc.org

NEWS.md

@@ -4,6 +4,8 @@
 
 -   The embedded Ace editor used in learnr exercises now defaults to a tab width of 2, aligning with the Tidyverse style guide (#761).
 
+-   Add a fallback to generate a comprehensible English feedback message for code that fails to parse because it contains non-ASCII characters. Previously, if i18next was unavailable, the feedback would contain uninterpolated i18next markup. Now the feedback is pre-interpolated so students will always see a comprehensible message (#765).
+
 # learnr 0.11.2
 
 -   Fixed an issue that prevented htmlwidgets from working in exercise code unless similar widgets were added to the tutorial prose (thanks @munoztd0 #744, #745).

R/exercise.R

@@ -1039,20 +1039,32 @@ exercise_check_unparsable_unicode <- function(exercise, error_message) {
   )
 }
 
-unparsable_unicode_message <- function(i18n_key, code, line, pattern, replacement_pattern = NULL) {
+unparsable_unicode_message <- function(
+  i18n_key, code, line, pattern, replacement_pattern = NULL
+) {
   code <- unlist(strsplit(code, "\n"))[[line]]
 
   character <- str_extract(code, pattern)
   highlighted_code <- exercise_highlight_unparsable_unicode(code, pattern, line)
 
-  suggestion <- NULL
-  if (!is.null(replacement_pattern)) {
-    suggestion <- html_code_block(str_replace_all(code, replacement_pattern))
+  suggestion <- if (!is.null(replacement_pattern)) {
+    html_code_block(str_replace_all(code, replacement_pattern))
+  } else {
+    NULL
+  }
+
+  code <- exercise_highlight_unparsable_unicode(code, pattern, line)
+
+  text <- i18n_translations()$en$translation$text[[i18n_key]]
+  text <- sub("{{character}}", character, text, fixed = TRUE)
+  text <- sub("{{code}}", highlighted_code, text, fixed = TRUE)
+  if (!is.null(suggestion)) {
+    text <- sub("{{suggestion}}", suggestion, text, fixed = TRUE)
   }
 
   i18n_div(
     paste0("text.", i18n_key),
-    HTML(i18n_translations()$en$translation$text[[i18n_key]]),
+    HTML(text),
     opts = list(
       character = character,
       code = highlighted_code,

tests/testthat/test-exercise.R

@@ -1171,52 +1171,42 @@ test_that("Errors with global setup code result in an internal error", {
 test_that("evaluate_exercise() returns message for unparsable non-ASCII code", {
   skip_if_not_pandoc("1.14")
 
+  expect_unparsable_message <- function(user_code, problem, key) {
+    ex <- mock_exercise(user_code = user_code)
+    feedback <- evaluate_exercise(ex, new.env())$feedback
+    expect_equal(feedback, exercise_check_code_is_parsable(ex)$feedback)
+    expect_match(feedback$message, regexp = key, fixed = TRUE)
+    for (character in problem) {
+      expect_match(feedback$message, regexp = character, fixed = TRUE)
+    }
+  }
+
   # Curly double quotes
-  ex <- mock_exercise(
-    user_code = "str_detect(\u201ctest\u201d, \u201ct.+t\u201d)"
-  )
-  result <- evaluate_exercise(ex, new.env())
-  expect_equal(result$feedback, exercise_check_code_is_parsable(ex)$feedback)
-  expect_match(result$feedback$message, "text.unparsablequotes")
-  expect_match(
-    result$feedback$message,
-    i18n_translations()$en$translation$text$unparsablequotes,
-    fixed = TRUE
+  expect_unparsable_message(
+    "str_detect(\u201ctest\u201d, \u201ct.+t\u201d)",
+    problem = c("\u201c", "\u201d"),
+    key = "text.unparsablequotes"
   )
 
   # Curly single quotes
-  ex <- mock_exercise(
-    user_code = "str_detect(\u2018test\u2019, \u2018t.+t\u2019)"
-  )
-  result <- evaluate_exercise(ex, new.env())
-  expect_equal(result$feedback, exercise_check_code_is_parsable(ex)$feedback)
-  expect_match(result$feedback$message, "text.unparsablequotes")
-  expect_match(
-    result$feedback$message,
-    i18n_translations()$en$translation$text$unparsablequotes,
-    fixed = TRUE
+  expect_unparsable_message(
+    "str_detect(\u2018test\u2019, \u2018t.+t\u2019)",
+    problem = c("\u2018", "\u2019"),
+    key = "text.unparsablequotes"
   )
 
   # En dash
-  ex     <- mock_exercise(user_code = "63 \u2013 21")
-  result <- evaluate_exercise(ex, new.env())
-  expect_equal(result$feedback, exercise_check_code_is_parsable(ex)$feedback)
-  expect_match(result$feedback$message, "text.unparsableunicodesuggestion")
-  expect_match(
-    result$feedback$message,
-    i18n_translations()$en$translation$text$unparsableunicodesuggestion,
-    fixed = TRUE
+  expect_unparsable_message(
+    "63 \u2013 21",
+    problem = "\u2013",
+    key = "text.unparsableunicodesuggestion"
   )
 
   # Plus-minus sign
-  ex     <- mock_exercise(user_code = "63 \u00b1 21")
-  result <- evaluate_exercise(ex, new.env())
-  expect_equal(result$feedback, exercise_check_code_is_parsable(ex)$feedback)
-  expect_match(result$feedback$message, "text.unparsableunicode")
-  expect_match(
-    result$feedback$message,
-    i18n_translations()$en$translation$text$unparsableunicode,
-    fixed = TRUE
+  expect_unparsable_message(
+    "63 \u00b1 21",
+    problem = "\u00b1",
+    key = "text.unparsableunicode"
   )
 })