Check that IFS changes don't leak

libexec/bats-core/bats-gather-tests

@@ -18,22 +18,27 @@ abort() {
   exit 1
 } >&2
 
+read_tags() {
+  local IFS=,
+  read -ra tags <<<"$1" || true
+  if ((${#tags[@]} > 0)); then
+    for ((i = 0; i < ${#tags[@]}; ++i)); do
+      bats_trim "tags[$i]" "${tags[$i]}"
+    done
+    bats_sort sorted_tags "${tags[@]}"
+    filter_tags_list+=("${sorted_tags[*]}")
+  else
+    filter_tags_list+=("")
+  fi
+}
+
 while [[ "$#" -ne 0 ]]; do
   case "$1" in
     --dummy-flag)
       ;;
     --filter-tags)
       shift
-      IFS=, read -ra tags <<<"$1" || true
-      if ((${#tags[@]} > 0)); then
-        for ((i = 0; i < ${#tags[@]}; ++i)); do
-          bats_trim "tags[$i]" "${tags[$i]}"
-        done
-        bats_sort sorted_tags "${tags[@]}"
-        IFS=, filter_tags_list+=("${sorted_tags[*]}")
-      else
-        filter_tags_list+=("")
-      fi
+      read_tags "$1"
       ;;
     --)
       shift 1
@@ -250,7 +255,6 @@ fi
 # shellcheck source=lib/bats-core/tracing.bash
 source "$BATS_ROOT/lib/bats-core/tracing.bash"
 
-
 bats_gather_tests_exit_trap() {
   local bats_gather_tests_exit_status=$?
   trap - ERR EXIT DEBUG

test/bats.bats

@@ -1499,13 +1499,5 @@ END_OF_ERR_MSG
 @test "IFS is preserved in all contexts" {
   bats_require_minimum_version 1.5.0
 
-  REENTRANT_RUN_PRESERVE+=(IFS EXPECTED_IFS)
-  export EXPECTED_IFS="$IFS"
-  export EXPECTED_IFS_MISMATCH_FILE="$BATS_TEST_TMPDIR/IFS_mismatches"
-
-  reentrant_run -0 bats "$FIXTURE_ROOT/preserve_IFS"
-
-  if [[ -e "$EXPECTED_IFS_MISMATCH_FILE" ]]; then
-    cat "$EXPECTED_IFS_MISMATCH_FILE"
-  fi
+  reentrant_run -0 bats --print-output-on-failure "$FIXTURE_ROOT/preserve_IFS" --filter-tags ''
 }

test/fixtures/bats/preserve_IFS/helper.bash

@@ -1,6 +1,8 @@
 check_ifs() {
-    if [[ ${EXPECTED_IFS?} != ${IFS} ]]; then
-        diff <(hexdump -c <<<"$EXPECTED_IFS") <(hexdump -c <<<"$IFS") >"${EXPECTED_IFS_MISMATCH_FILE?}"
+    if [[ "$IFS" != $' \t\n' ]]; then
+        echo "${FUNCNAME[*]}"
+        echo "${BASH_SOURCE[*]}"
+        hexdump -c <<<"$IFS"
         exit 1
-    fi
+    fi >&2
 }