paleolimbot commented on code in PR #12817:
URL: https://github.com/apache/arrow/pull/12817#discussion_r853361427
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r/R/array.R:
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@@ -217,6 +217,93 @@ Array$create <- function(x, type = NULL) {
Array$import_from_c <- ImportArray
+#' Convert an object to an Arrow Array
+#'
+#' Whereas `Array$create()` constructs an [Array] from the built-in data types
+#' for which the Arrow package implements fast converters, `as_arrow_array()`
+#' provides a means by which other packages can define conversions to Arrow
+#' objects.
+#'
+#' @param x An object to convert to an Arrow Array
+#' @param ... Passed to S3 methods
+#' @param type A [type][data-type] for the final Array. A value of `NULL`
+#' will default to the type guessed by [type()].
+#'
+#' @return An [Array].
+#' @export
+#'
+#' @examplesIf arrow_available()
+#' as_arrow_array(1:5)
+#'
+as_arrow_array <- function(x, ..., type = NULL) {
+ UseMethod("as_arrow_array")
+}
+
+#' @rdname as_arrow_array
+#' @export
+as_arrow_array.Array <- function(x, ..., type = NULL) {
+ if (is.null(type)) {
+ x
+ } else {
+ x$cast(type)
+ }
+}
+
+#' @rdname as_arrow_array
+#' @export
+as_arrow_array.ChunkedArray <- function(x, ..., type = NULL) {
+ concat_arrays(!!! x$chunks, type = type)
+}
+
+#' @rdname as_arrow_array
+#' @export
+as_arrow_array.vctrs_vctr <- function(x, ..., type = NULL) {
+ if (is.null(type)) {
+ vctrs_extension_array(x)
+ } else if (inherits(type, "VctrsExtensionType")) {
+ vctrs_extension_array(
+ x,
+ ptype = type$ptype(),
+ storage_type = type$storage_type()
+ )
+ } else {
+ NextMethod()
+ }
+}
+
+#' @export
+as_arrow_array.POSIXlt <- function(x, ..., type = NULL) {
+ as_arrow_array.vctrs_vctr(x, ..., type = type)
Review Comment:
You were totally right...I was using `NextMethod()` to re-use the error
generation code, so you could trigger an infinite loop with an invalid `type`
and an oddly formed `POSIXlt`. A better approach was to pull the error code
into its own function (this also came up in the `data.frame` method that was
needed to make nested extension types work).
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