[GitHub] [arrow] thisisnic commented on a diff in pull request #14093: ARROW-17416: [R] Implement lubridate::with_tz and lubridate::force_tz

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

thisisnic commented on code in PR #14093:
URL: https://github.com/apache/arrow/pull/14093#discussion_r1064476780


##########
r/R/dplyr-funcs-datetime.R:
##########
@@ -429,6 +430,78 @@ register_bindings_datetime_conversion <- function() {
   })
 }
 
+register_bindings_datetime_timezone <- function() {
+  register_binding(
+    "lubridate::force_tz",
+    function(time, tzone = "", roll_dst = c("error", "post")) {
+      if (length(roll_dst) == 1L) {
+        roll_dst <- c(roll_dst, roll_dst)
+      } else if (length(roll_dst) != 2L) {
+        arrow_not_supported("`roll_dst` length != 1 or 2")
+      }
+
+      nonexistent <- switch(
+        roll_dst[1],
+        "error" = 0L,
+        "boundary" = 2L,
+        arrow_not_supported("`roll_dst` != 'error' or 'boundary' for nonexistent times")

Review Comment:
   ```suggestion
           arrow_not_supported("`roll_dst` value must be 'error' or 'boundary' for non-existent times; other values")
   ```
   



##########
r/R/dplyr-funcs-datetime.R:
##########
@@ -429,6 +430,78 @@ register_bindings_datetime_conversion <- function() {
   })
 }
 
+register_bindings_datetime_timezone <- function() {
+  register_binding(
+    "lubridate::force_tz",
+    function(time, tzone = "", roll_dst = c("error", "post")) {
+      if (length(roll_dst) == 1L) {
+        roll_dst <- c(roll_dst, roll_dst)
+      } else if (length(roll_dst) != 2L) {
+        arrow_not_supported("`roll_dst` length != 1 or 2")
+      }
+
+      nonexistent <- switch(
+        roll_dst[1],
+        "error" = 0L,
+        "boundary" = 2L,
+        arrow_not_supported("`roll_dst` != 'error' or 'boundary' for nonexistent times")
+      )
+
+      ambiguous <- switch(
+        roll_dst[2],
+        "error" = 0L,
+        "pre" = 1L,
+        "post" = 2L,
+        arrow_not_supported("`roll_dst` != 'error', 'pre', or 'post' for ambiguous times")

Review Comment:
   This one too



##########
r/R/dplyr-funcs-datetime.R:
##########
@@ -429,6 +430,78 @@ register_bindings_datetime_conversion <- function() {
   })
 }
 
+register_bindings_datetime_timezone <- function() {
+  register_binding(
+    "lubridate::force_tz",
+    function(time, tzone = "", roll_dst = c("error", "post")) {
+      if (length(roll_dst) == 1L) {
+        roll_dst <- c(roll_dst, roll_dst)
+      } else if (length(roll_dst) != 2L) {
+        arrow_not_supported("`roll_dst` length != 1 or 2")

Review Comment:
   ```suggestion
           arrow_not_supported("`roll_dst` must be 1 or 2 items long; other lengths")
   ```
   This phrasing could be a bit clearer here - I've updated this to be more descriptive, and use "must" phrasing, as per the tidyverse style guide.



##########
r/R/dplyr-funcs-datetime.R:
##########
@@ -429,6 +430,78 @@ register_bindings_datetime_conversion <- function() {
   })
 }
 
+register_bindings_datetime_timezone <- function() {
+  register_binding(
+    "lubridate::force_tz",
+    function(time, tzone = "", roll_dst = c("error", "post")) {
+      if (length(roll_dst) == 1L) {
+        roll_dst <- c(roll_dst, roll_dst)
+      } else if (length(roll_dst) != 2L) {
+        arrow_not_supported("`roll_dst` length != 1 or 2")
+      }
+
+      nonexistent <- switch(
+        roll_dst[1],
+        "error" = 0L,
+        "boundary" = 2L,
+        arrow_not_supported("`roll_dst` != 'error' or 'boundary' for nonexistent times")
+      )
+
+      ambiguous <- switch(
+        roll_dst[2],
+        "error" = 0L,
+        "pre" = 1L,
+        "post" = 2L,
+        arrow_not_supported("`roll_dst` != 'error', 'pre', or 'post' for ambiguous times")
+      )
+
+      if (identical(tzone, "")) {
+        tzone <- Sys.timezone()
+      }
+
+      if (!inherits(time, "Expression")) {
+        time <- Expression$scalar(time)
+      }
+
+      # Non-UTC timezones don't work here and getting them to do so was too
+      # hard to do in the initial PR because there is no way in Arrow to
+      # "unapply" a UTC offset (i.e., the reverse of assume_timezone).
+      if (!time$type()$timezone() %in% c("", "UTC")) {
+        arrow_not_supported(
+          paste0("force_tz() from timezone `", time$type()$timezone(), "`")
+        )

Review Comment:
   Please can we add something mentioning the fact that UTC timezones *are* supported to this error message, so it's clearer to users what they can and can't do?



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