add: helper function to create reference index

.Rbuildignore

@@ -3,6 +3,7 @@
 ^LICENSE\.md$
 ^build_vvCommander.R
 ^\.github$
+^helperfunctions$
 ^_pkgdown\.yml$
 ^docs$
 ^pkgdown$

helperfunctions/data_reference_index_missing.R

@@ -0,0 +1,20 @@
+library(purrr)
+data_reference_index_missing <- function(pkg = ".", depth = 1L) {
+  pkg <- pkgdown:::as_pkgdown(pkg)
+
+  meta <- pkg$meta[["reference"]] %||% pkgdown:::default_reference_index(pkg)
+  if (length(meta) == 0) {
+    return(list())
+  }
+
+  # Cross-reference complete list of topics vs. topics found in index page
+  all_topics <- meta %>%
+    map(~ pkgdown:::select_topics(.$contents, pkg$topics)) %>%
+    reduce(union)
+  in_index <- seq_along(pkg$topics$name) %in% all_topics
+
+  missing <- !in_index & !pkg$topics$internal
+  pkg$topics$name[missing]
+}
+
+data_reference_index_missing()