[GitHub] [arrow] dragosmg commented on a diff in pull request #13196: ARROW-16407: [R] Extend `parse_date_time` to cover hour, dates, and minutes components

[GitBox <gi...@apache.org>]

dragosmg commented on code in PR #13196:
URL: https://github.com/apache/arrow/pull/13196#discussion_r878259012


##########
r/R/dplyr-datetime-helpers.R:
##########
@@ -201,19 +213,130 @@ build_formats <- function(orders) {
 }
 
 build_format_from_order <- function(order) {
-  year_chars <- c("%y", "%Y")
-  month_chars <- c("%m", "%B", "%b")
-  day_chars <- "%d"
-
-  outcome <- switch(
-    order,
-    "ymd" = expand.grid(year_chars, month_chars, day_chars),
-    "ydm" = expand.grid(year_chars, day_chars, month_chars),
-    "mdy" = expand.grid(month_chars, day_chars, year_chars),
-    "myd" = expand.grid(month_chars, year_chars, day_chars),
-    "dmy" = expand.grid(day_chars, month_chars, year_chars),
-    "dym" = expand.grid(day_chars, year_chars, month_chars)
+  char_list <- list(
+    "y" = c("%y", "%Y"),
+    "m" = c("%m", "%B", "%b"),
+    "d" = "%d",
+    "H" = "%H",
+    "M" = "%M",
+    "S" = "%S"
+  )
+
+  split_order <- strsplit(order, split = "")[[1]]
+
+  outcome <- expand.grid(char_list[split_order])
+  formats_with_sep <- do.call(paste, c(outcome, sep = "-"))
+  formats_without_sep <- do.call(paste, c(outcome, sep = ""))
+  c(formats_with_sep, formats_without_sep)

Review Comment:
   What if the data has a mixture of both? I imagine it could happen in very messy datasets. So probably more like:
   ```r
   ifelse(grepl("-", col), try_both_formats, try_only_without_sep) 
   ```



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