add error message for class "difftime" (#232)

closes #215 

Adding an error message for now for clarity - we can revisit supporting
the "difftime" class type based on user requests.

NEWS.md

@@ -1,4 +1,5 @@
 ## rlistings 0.2.9.9008
+ * Added an error message for listings with variables of `difftime` class.
 
 ## rlistings 0.2.9
  * Added `truetype` font support based on new `formatters` api, by @gmbecker.

R/rlistings.R

@@ -168,6 +168,10 @@ as_listing <- function(df,
     )
   }
 
+  if (any(sapply(df, inherits, "difftime"))) {
+    stop("One or more variables in the dataframe have class 'difftime'. Please convert to factor or character.")
+  }
+
   df <- as_tibble(df)
   varlabs <- var_labels(df, fill = TRUE)
   o <- do.call(order, df[key_cols])

tests/testthat/test-listings.R

@@ -350,3 +350,17 @@ testthat::test_that("split_into_pages_by_var works as expected", {
   )
   testthat::expect_identical(lsting, lsting_id)
 })
+
+testthat::test_that("appropriate error message returned for 'difftime' class", {
+  tmp_data <- ex_adae[1:100, ]
+  class(tmp_data$study_duration_secs) <- "difftime"
+
+  testthat::expect_error(as_listing(
+    tmp_data,
+    key_cols = c("USUBJID", "AGE"),
+    disp_cols = "study_duration_secs",
+    main_title = "title",
+    main_footer = "foot"
+  ) %>%
+    split_into_pages_by_var("SEX", page_prefix = "Patient Subset - Sex"))
+})