tests: Use variable redirections to dup std{out,err}

Previously, we hardcoded file descriptors 3 and 4 for duplicating
stdandard output/error respectively.  In preparation for keeping
inherited FDs open, switch to using bash's variable redirection feature
to dynamically assign FDs.

This feature is only available from bash 4.1 onwards, so this marks the
end of our support for bash 3.  macOS users will need to install a
modern bash version to run our tests.

3 files changed, 18 insertions, 29 deletions

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 72037e3..ff0ff6f 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -52,7 +52,9 @@ jobs:
 
       - name: Install dependencies
         run: |
-          brew install expect
+          brew install \
+              bash \
+              expect
 
       - name: Run tests
         run: |
diff --git a/tests/run.sh b/tests/run.sh
index 4a159f9..85d961f 100644
--- a/tests/run.sh
+++ b/tests/run.sh
@@ -28,7 +28,7 @@ debug_err() {
     callers | while read -r line func file; do
         if [ "$func" = source ]; then
             local cmd="$(awk "NR == $line" "$file" 2>/dev/null)" || :
-            debug "$file" $line "${RED}error $ret${RST}" "$cmd" >&4
+            debug "$file" $line "${RED}error $ret${RST}" "$cmd" >&$DUPERR
             break
         fi
     done
@@ -73,21 +73,9 @@ bg_test() {
     return $ret
 }
 
-# Wait for any background job to complete
-if ((BASH_VERSINFO[0] > 4 || (BASH_VERSINFO[0] == 4 && BASH_VERSINFO[1] >= 3))); then
-    wait_any() {
-        wait -n
-    }
-else
-    wait_any() {
-        read -ra jobs < <(jobs -p)
-        wait ${jobs[0]}
-    }
-fi
-
 # Wait for a background test to finish
 wait_test() {
-    wait_any
+    wait -n
     ret=$?
     ((BG--))
 
@@ -197,7 +185,7 @@ skip() {
         caller | {
             read -r line file
             printf "${BOL}"
-            debug "$file" $line "" "$(awk "NR == $line" "$file")" >&3
+            debug "$file" $line "" "$(awk "NR == $line" "$file")" >&$DUPOUT
         }
     fi
 
@@ -252,8 +240,8 @@ bfs_verbose() {
         (
             # Close some fds to make room for the pipe,
             # even with extremely low ulimit -n
-            exec >&- 4>&-
-            exec >&3 3>&-
+            exec >&- {DUPERR}>&-
+            exec >&$DUPOUT {DUPOUT}>&-
             color bfs_verbose_impl "$@"
         )
     fi
@@ -306,7 +294,7 @@ invoke_bfs() {
 
     local ret=0
     # Close the logging fds
-    "${BFS[@]}" "$@" 3>&- 4>&- || ret=$?
+    "${BFS[@]}" "$@" {DUPOUT}>&- {DUPERR}>&- || ret=$?
 
     # Allow bfs to fail, but not crash
     if ((ret > 125)); then
@@ -391,7 +379,7 @@ diff_output() {
     if ((UPDATE)); then
         cp "$OUT" "$GOLD"
     else
-        $DIFF -u "$GOLD" "$OUT" >&4
+        $DIFF -u "$GOLD" "$OUT" >&$DUPERR
     fi
 }
 
diff --git a/tests/util.sh b/tests/util.sh
index 5bd3328..686cc77 100644
--- a/tests/util.sh
+++ b/tests/util.sh
@@ -68,7 +68,7 @@ stdenv() {
 
     # Close stdin so bfs doesn't think we're interactive
     # dup() the standard fds for logging even when redirected
-    exec </dev/null 3>&1 4>&2
+    exec </dev/null {DUPOUT}>&1 {DUPERR}>&2
 }
 
 # Drop root priviliges or bail
@@ -159,19 +159,18 @@ defer() {
 
 # Pop a single command from the defer stack and run it
 pop_defer() {
-    local i=$((${#DEFER_CMDS[@]} - 1))
-    local cmd="${DEFER_CMDS[$i]}"
-    local file="${DEFER_FILES[$i]}"
-    local line="${DEFER_LINES[$i]}"
-    unset "DEFER_CMDS[$i]"
-    unset "DEFER_FILES[$i]"
-    unset "DEFER_LINES[$i]"
+    local cmd="${DEFER_CMDS[-1]}"
+    local file="${DEFER_FILES[-1]}"
+    local line="${DEFER_LINES[-1]}"
+    unset "DEFER_CMDS[-1]"
+    unset "DEFER_FILES[-1]"
+    unset "DEFER_LINES[-1]"
 
     local ret=0
     eval "$cmd" || ret=$?
 
     if ((ret != 0)); then
-        debug "$file" $line "${RED}error $ret${RST}" "defer $cmd" >&4
+        debug "$file" $line "${RED}error $ret${RST}" "defer $cmd" >&$DUPERR
     fi
 
     return $ret