cache regex in namespace instead of recomputing it at runtime

Author: MichaelChirico

R/data.table.R

@@ -96,19 +96,19 @@ replace_dot_alias = function(e) {
   x
 }
 
+# a slightly wonky workaround so that this still works in non-English sessions, #4989
+# generate this at run time (as opposed to e.g. onAttach) since session language is
+#   technically OK to update (though this should be rare), and since it's low-cost
+#   to do so here because we're about to error anyway.
+.missing_obj_regex = gsub(
+  "'____missing_datatable_variable____'",
+  "'(?<obj_name>[^']+)'",
+  # expression() to avoid "no visible binding for global variable" note from R CMD check
+  conditionMessage(tryCatch(eval(expression(`____missing_datatable_variable____`)), error=identity)),
+  fixed=TRUE
+)
 .checkTypos = function(err, ref) {
-  # a slightly wonky workaround so that this still works in non-English sessions, #4989
-  # generate this at run time (as opposed to e.g. onAttach) since session language is
-  #   technically OK to update (though this should be rare), and since it's low-cost
-  #   to do so here because we're about to error anyway.
-  missing_obj_fmt = gsub(
-    "'____missing_datatable_variable____'",
-    "'(?<obj_name>[^']+)'",
-    # expression() to avoid "no visible binding for global variable" note from R CMD check
-    conditionMessage(tryCatch(eval(expression(`____missing_datatable_variable____`)), error=identity)),
-    fixed=TRUE
-  )
-  idx = regexpr(missing_obj_fmt, err$message, perl=TRUE)
+  idx = regexpr(.missing_obj_regex, err$message, perl=TRUE)
   if (idx > 0L) {
     start = attr(idx, "capture.start", exact=TRUE)[ , "obj_name"]
     used = substr(