Empty input for styling does not cause error

R/nested.R

@@ -7,7 +7,9 @@
 #' @return A nested parse table. See [tokenize()] for details on the columns
 #'   of the parse table.
 compute_parse_data_nested <- function(text) {
-  parse_data <- tokenize(text) %>%
+  tokenized <- tokenize(text)
+  if (nrow(tokenized) == 0) return(data_frame())
+  parse_data <- tokenized %>%
     add_terminal_token_before() %>%
     add_terminal_token_after()
 

R/transform.R

@@ -84,6 +84,14 @@ make_transformer <- function(transformers) {
 #' @inheritParams apply_transformers
 parse_transform_serialize <- function(text, transformers) {
   pd_nested <- compute_parse_data_nested(text)
+
+  if (nrow(pd_nested) == 0) {
+    warning(
+      "Text to style did not contain any tokens. Returning empty string.",
+      call. = FALSE
+    )
+    return("")
+  }
   transformed_pd <- apply_transformers(pd_nested, transformers)
   # TODO verify_roundtrip
   flattened_pd <- post_visit(transformed_pd, list(extract_terminals)) %>%

tests/testthat/exception_handling/empty_file.R

@@ -0,0 +1 @@
+

tests/testthat/test-exception_handling.R

@@ -6,7 +6,19 @@ test_that("style_text returns custom error", {
 
 test_that("style_file returns custom error", {
   expect_warning(
-    style_file(testthat_file("exception_handling", "/parser-error.R")),
+    style_file(testthat_file("exception_handling", "parser-error.R")),
     "When processing"
   )
 })
+
+
+test_that("style_text with no tokens returns empty string and warning", {
+  expect_warning(style_text("\n\n"), "not contain any tokens.")
+})
+
+test_that("style_file with no tokens returns empty string and warning", {
+  expect_warning(
+    style_file(testthat_file("exception_handling", "empty_file.R")),
+    "not contain any tokens."
+  )
+})