Only support hours without zero-padding

Remove support for non-zero-padded minutes and seconds. The ISO 8601
standard requires all time components be zero-padded. That said, we
do support hours that aren't zero-padded, for convenience.

Also make the validation regex stricter. The first digit for minutes
and seconds cannot be > 5. Separate regex into multiple pieces, to
make them easier to understand later.

See joshuaulrich#326. See joshuaulrich#327.

R/xts.methods.R

@@ -21,11 +21,19 @@
 
 .subsetTimeOfDay <- function(x, fromTimeString, toTimeString) {
   validateTimestring <- function(time) {
-    if (isFALSE(grepl(paste0("^(([0-9]{1,2}|",
-                             "[0-9]{1,2}:[0-9]{1,2})$)|",
-                             "([0-9]{1,2}:[0-9]{1,2}:[0-9]{1,2}($|?(.[0-9]+)))"),
-                      time)))
-      stop("Supply time-of-day subsetting in the format of T%H:%M:%OS/T%H:%M:%OS")
+    h    <- "(?:[01]?\\d|2[0-3])"
+    hm   <- paste0(h, "(?::[0-5]\\d)")
+    hms  <- paste0(hm, "(?::[0-5]\\d)")
+    hmsS <- paste0(hms, "(?:\\.\\d{1,9})?")
+    pattern <- paste(h, hm, hms, hmsS, sep = ")$|^(")
+    pattern <- paste0("^(", pattern, "$)")
+
+    if (!grepl(pattern, time)) {
+      # FIXME: this isn't necessarily true...
+      # colons aren't required, and neither are all of the components
+      stop("Supply time-of-day subsetting in the format of T%H:%M:%OS/T%H:%M:%OS",
+           call. = FALSE)
+    }
   }
   padTimestring <- function(time) {
     ifelse(grepl("^[0-9]{1,2}$", time), paste0(time, ":00"), time)

inst/unitTests/runit.subset-time-of-day.R

@@ -65,9 +65,10 @@ test.time_of_day_by_second <- function() {
                    983L, 984L, 985L, 986L)])
 
   checkIdentical(.index(x["T01:58:05/T02:01:09"]), i1)
-  # Can omit 0 padding, as is possible by default with as.POSIXct():
-  checkIdentical(.index(x["T01:58:5/T02:1:9"]), i1)
-  checkIdentical(.index(x["T01:58:05.000/T02:01:09.000"]), i1)
+  # Can only omit 0 padding for hours. Only for convenience because it does
+  # not conform to the ISO 8601 standard, which requires padding with zeros.
+  checkIdentical(.index(x["T1:58:05/T2:01:09"]), i1)
+  checkIdentical(.index(x["T1:58:05.000/T2:01:09.000"]), i1)
 }
 
 test.time_of_day_end_before_start <- function() {