cronic: run the command with the caller's shell options, and capture all of the subshell's output

cronic

@@ -17,6 +17,20 @@
 # This script runs under bash 3.2, which is /bin/bash on macOS, so it uses a
 # feature of a later bash only after checking the version.
 
+# The caller's shell options that this script changes, as the letters that `$-`
+# uses for them, which this script restores for the command.  They include any
+# that the caller passed by exporting SHELLOPTS.  This script turns xtrace off,
+# so that its own commands are not traced to stderr, which would make every run
+# produce output; the redirection discards the trace of `set +x` itself.  It
+# turns allexport off, so that its own variables are not exported to the
+# command; `cronic_caller_flags`, which is assigned before that, is un-exported
+# explicitly.
+{
+  cronic_caller_flags=${-//[^aeux]/}
+  set +ax
+  export -n cronic_caller_flags
+} 2> /dev/null
+
 # Exit if a command exits with a non-zero status, and treat unset variables
 # as an error.
 set -eu
@@ -163,11 +177,20 @@ fi
 # The command runs in a subshell rather than in this shell, so that a builtin
 # such as `exit` or `exec` cannot end this script before it reports.
 # `command` because a function of this script, such as `cronic_usage`, would
-# otherwise run in place of a program of the same name.
+# otherwise run in place of a program of the same name.  The redirections
+# apply to the whole subshell, so that they also capture what it writes after
+# the command finishes, such as the output of an EXIT trap that the command
+# sets.  The subshell restores the caller's `-a`, `-e`, `-u`, and `-x` options,
+# replacing this script's, for a builtin and also for a bash script when the
+# caller exported SHELLOPTS.  It turns off this script's nounset (errexit is off
+# already) in the same command that turns on the caller's options, so that only
+# the command is traced.  The `:+` avoids a bare `-`, which has a special
+# meaning to `set`.
 set +e
 (
-  command -- "$@" > "$cronic_out" 2> "$cronic_trace"
-)
+  set +u${cronic_caller_flags:+ -$cronic_caller_flags}
+  command -- "$@"
+) > "$cronic_out" 2> "$cronic_trace"
 cronic_result=$?
 set -e
 

tests/cronic-test/cronic-test.sh

@@ -268,6 +268,83 @@ check "builtin command" 0 silent :
 # A builtin that would end the shell does not prevent the report.
 check "exit builtin" 3 report exit 3
 check "exec builtin" 3 report exec "$work/trace-only" 3
+# Output that the subshell writes after the command finishes, such as from an
+# EXIT trap that the command sets, is captured rather than leaked.
+check "EXIT trap writes to stderr" 0 "report:^from the trap$" \
+  trap 'echo "from the trap" >&2' EXIT
+check "EXIT trap writes to stdout" 0 silent trap 'echo "from the trap"' EXIT
+# A builtin runs with `set +u`, as it would in an ordinary shell.
+# shellcheck disable=SC2016 # The expansion is for the wrapped command to do.
+check "builtin with an unset variable" 0 silent \
+  eval ': "$cronic_test_unset_variable"'
+# When the caller exports SHELLOPTS, a bash script runs with the caller's
+# options rather than with `cronic`'s own `set -eu`.  BASH_ENV is empty so that
+# the script runs no startup file.
+# Creates "$work/cronic-with-NAME", which runs `cronic` with SHELLOPTS exported,
+# after `set OPTION` if OPTION is given.
+make_cronic_wrapper() { # NAME [OPTION]
+  {
+    echo "#!/bin/bash"
+    if [ $# -gt 1 ]; then
+      echo "set $2"
+    fi
+    echo "export SHELLOPTS"
+    echo "exec \"$CRONIC\" \"\$@\""
+  } > "$work/cronic-with-$1"
+  chmod +x "$work/cronic-with-$1"
+}
+make_cronic_wrapper shellopts
+make_cronic_wrapper nounset -u
+make_cronic_wrapper errexit -e
+make_cronic_wrapper allexport -a
+# The wrapper's own trace goes to /dev/null, and `cronic` reads no startup
+# file, so that any trace in the output comes from `cronic`.
+cat > "$work/cronic-with-xtrace" << EOF
+#!/bin/bash
+unset BASH_ENV
+exec 3>&2 2> /dev/null
+set -x
+export SHELLOPTS
+exec "$CRONIC" "\$@" 2>&3 3>&-
+EOF
+chmod +x "$work/cronic-with-xtrace"
+saved_cronic="$CRONIC"
+CRONIC="$work/cronic-with-shellopts"
+# shellcheck disable=SC2016 # The expansion is for the wrapped command to do.
+check "bash script with an unset variable, SHELLOPTS exported" 0 silent \
+  env BASH_ENV= bash -c ': "$cronic_test_unset_variable"'
+check "bash script with a failing command, SHELLOPTS exported" 0 silent \
+  env BASH_ENV= bash -c 'false; true'
+CRONIC="$work/cronic-with-nounset"
+# shellcheck disable=SC2016 # The expansion is for the wrapped command to do.
+check "bash script with an unset variable, caller's nounset exported" 127 \
+  "report:cronic_test_unset_variable" \
+  env BASH_ENV= bash -c ': "$cronic_test_unset_variable"'
+CRONIC="$work/cronic-with-errexit"
+check "bash script with a failing command, caller's errexit exported" 1 report \
+  env BASH_ENV= bash -c 'false; true'
+# When the caller exports allexport, `cronic` does not export its own variables
+# to the command, but a variable that the command assigns is exported.
+CRONIC="$work/cronic-with-allexport"
+check "no cronic variables exported, caller's allexport exported" 0 silent \
+  sh -c '! env | grep -q "^cronic_"'
+# shellcheck disable=SC2016 # The expansion is for the wrapped command to do.
+check "command's variable exported, caller's allexport exported" 0 silent \
+  eval 'cronic_test_variable=1; sh -c "[ \"\$cronic_test_variable\" = 1 ]"'
+# When the caller exports xtrace, `cronic` traces only the command, not itself.
+CRONIC="$work/cronic-with-xtrace"
+check "bash script, caller's xtrace exported" 0 silent \
+  env BASH_ENV= bash -c 'true'
+check "bash script that fails, caller's xtrace exported" 1 "report:^+ false$" \
+  env BASH_ENV= bash -c 'false'
+if grep -q cronic_ "$work/output"; then
+  echo "FAIL: caller's xtrace exported: the report traces cronic itself:"
+  cat "$work/output"
+  status=1
+else
+  echo "PASS: caller's xtrace exported: the report does not trace cronic itself"
+fi
+CRONIC="$saved_cronic"
 
 # The wrapped command sees the caller's exported variables unchanged.  For
 # each variable that `cronic` assigns, the caller exports that name in