run() now returns with stderr = NULL if stderr is redirected to

stdout.

This also fixes an error when interrupting a `run()` with a redirected
standard error.

NEWS.md

@@ -1,6 +1,9 @@
 
 # processx (development version)
 
+* `run()` now sets `stderr` to `NULL` in the result (instead of an empty
+  string), if the standard error was redirected to the standard output.
+
 # processx 3.5.2
 
 * `run()` now does not truncate stdout and stderr when the output

R/run.R

@@ -211,7 +211,7 @@ run <- function(
   runcall <- sys.call()
   resenv <- new.env(parent = emptyenv())
   has_stdout <- !is.null(stdout) && stdout == "|"
-  has_stderr <- !is.null(stderr) && stderr %in% c("|", "2>&1")
+  has_stderr <- !is.null(stderr) && stderr == "|"
 
   if (has_stdout) {
     resenv$outbuf <- make_buffer()
@@ -279,7 +279,7 @@ run_manage <- function(proc, timeout, spinner, stdout, stderr,
   start_time <- proc$get_start_time()
 
   has_stdout <- !is.null(stdout) && stdout == "|"
-  has_stderr <- !is.null(stderr) && stderr %in% c("|", "2>&1")
+  has_stderr <- !is.null(stderr) && stderr == "|"
 
   pushback_out <- ""
   pushback_err <- ""

tests/testthat/test-run.R

@@ -92,7 +92,7 @@ test_that("stderr_to_stdout", {
   expect_equal(out$status, 0L)
   expect_equal(
     out$stdout, paste0("o1e1o2e2", if (is_windows()) "\r", "\n"))
-  expect_equal(out$stderr, "")
+  expect_equal(out$stderr, NULL)
   expect_false(out$timeout)
 })