add a wrapper function system3() based on system2() to mark the c…

…haracter output of `system2()` as UTF-8 if appropriate

to avoid problems like rstudio/blogdown@e4a3f38

DESCRIPTION

@@ -1,7 +1,7 @@
 Package: xfun
 Type: Package
 Title: Supporting Functions for Packages Maintained by 'Yihui Xie'
-Version: 0.28.5
+Version: 0.28.6
 Authors@R: c(
   person("Yihui", "Xie", role = c("aut", "cre", "cph"), email = "[email protected]", comment = c(ORCID = "0000-0003-0645-5666")),
   person("Wush", "Wu", role = "ctb"),

NAMESPACE

@@ -104,6 +104,7 @@ export(strict_list)
 export(stringsAsStrings)
 export(strings_please)
 export(submit_cran)
+export(system3)
 export(tinify)
 export(tojson)
 export(tree)

NEWS.md

@@ -6,6 +6,8 @@
 
 - Added functions `rest_api_raw()` and `rest_api()` to get data from a REST API; also added the function `github_api()` to get data from the Github API based on `rest_api_raw()`.
 
+- Added a wrapper function `system3()` based on `system2()` to mark the character output of `system2()` as UTF-8 if appropriate.
+
 # CHANGES IN xfun VERSION 0.28
 
 - Added a new function `url_accessible()` to test if a URL can be downloaded.

R/command.R

@@ -1,3 +1,28 @@
+#' Run \code{system2()} and mark its character output as UTF-8 if appropriate
+#'
+#' This is a wrapper function based on \code{system2()}. If \code{system2()}
+#' returns character output (e.g., with the argument \code{stdout = TRUE}),
+#' check if the output is encoded in UTF-8. If it is, mark it with UTF-8
+#' explicitly.
+#' @param ... Passed to \code{\link{system2}()}.
+#' @return The value returned by \code{system2()}.
+#' @export
+#' @examplesIf interactive()
+#' a = shQuote(c('-e', 'print(intToUtf8(c(20320, 22909)))'))
+#' x2 = system2('Rscript', a, stdout = TRUE)
+#' Encoding(x2)  # unknown
+#'
+#' x3 = xfun::system3('Rscript', a, stdout = TRUE)
+#' # encoding of x3 should be UTF-8 if the current locale is UTF-8
+#' !l10n_info()[['UTF-8']] || Encoding(x3) == 'UTF-8'  # should be TRUE
+system3 = function(...) {
+  res = system2(...)
+  if (is.character(res)) {
+    if (all(is_utf8(res))) Encoding(res) = 'UTF-8'
+  }
+  if (is.integer(res) && res == 0) invisible(res) else res
+}
+
 #' Run OptiPNG on all PNG files under a directory
 #'
 #' Call the command \command{optipng} via \code{system2()} to optimize all PNG