Run help50 COMMAND as though COMMAND were typed directly

etc/profile.d/help50.sh

@@ -22,6 +22,14 @@ function _help50() {
     HISTFILE=$histfile history -a
     local argv=$(HISTFILE=$histfile history 1 | cut -c 8-) # Could technically contain multiple commands, separated by ; or &&
     rm --force $histfile
+
+    # If run via `help50 COMMAND`, it's COMMAND that ran, so that's what helpers should see
+    if [[ "$argv" =~ ^help50[[:space:]]+([^[:space:]].*)$ ]]; then
+        local wrapped="${BASH_REMATCH[1]}"
+        if ! [[ "$wrapped" =~ ^(disable|enable|is-enabled|start|status|stop|-h|--help)([[:space:]]|$) ]]; then
+            argv="$wrapped"
+        fi
+    fi
     local argv0=$(echo "$argv" | awk '{print $1}') # Assume for simplicity it's just a single command
 
     # Remove any of these aliases
@@ -132,6 +140,20 @@ function _rhetorical() {
     _alert "That was a rhetorical question. <3"
 }
 
+# Run `help50 COMMAND` in this very shell, as though COMMAND had been typed directly, so that
+# aliases (e.g., rm -i), functions, and builtins like cd behave exactly as they would have;
+# /opt/cs50/bin/help50 handles the rest (and COMMAND too, outside of a help50 session)
+function help50() {
+    case "$1" in
+        disable|enable|is-enabled|start|status|stop|""|-h|--help)
+            command help50 "$@"
+            ;;
+        *)
+            eval "$(printf '%q ' "$@")"
+            ;;
+    esac
+}
+
 # Default helpers, overridable (e.g., by cs50/codespace) by defining them before this file is sourced:
 #   _helped              last command succeeded
 #   _helpful ADVICE      a helper had advice for the failed command

opt/cs50/bin/help50

@@ -1,10 +1,5 @@
 #!/bin/bash
 
-# If root
-if [[ `id -u` -eq 0 ]]; then
-    exit 1
-fi
-
 function _disable() {
     touch /tmp/help50.lock
 }
@@ -80,28 +75,51 @@ function _stop() {
     kill -SIGTERM $ggppid
 }
 
+# Run a command as though typed directly. Students used to run `help50 make foo`; help now
+# arrives automatically after any failed command, so just run the command, with the same
+# exit status, and let the shell's prompt hook handle the rest. (Within a help50 session,
+# /etc/profile.d/help50.sh defines a `help50` function that runs the command in the shell
+# itself instead, so that aliases, functions, and `cd` behave as they would directly.)
+function _run() {
+    if [[ -n "$(type -P -- "$1")" ]]; then
+        exec "$@"
+    elif [[ "$1" == */* || -n "$(type -t -- "$1")" ]]; then # Path, builtin, or keyword, e.g., ./foo.c, cd
+
+        # Let bash itself report errors (e.g., Permission denied, Is a directory, No such
+        # file or directory), as it would have directly, so that helpers recognize them
+        bash -c "$(printf '%q ' "$@")" 2> >(sed 's/^bash: line [0-9]*: /bash: /' >&2)
+        local status=$?
+        wait $! 2> /dev/null # For sed to finish, lest its output arrive after the prompt
+        exit $status
+    else # Fail the way the shell would, so that helpers recognize it
+        echo "bash: $1: command not found" >&2
+        exit 127
+    fi
+}
+
+function _usage() {
+    echo "Usage: help50 COMMAND [ARGS...]"
+    echo
+    echo "Runs COMMAND. If it fails, help appears automatically, as it now does for any"
+    echo "command you run, so you can also just run COMMAND directly."
+    echo
+    echo "Other usage: help50 [disable|enable|is-enabled|start|status|stop]"
+}
+
 # Parse argument
 case "$1" in
-    disable)
-        _disable
-        ;;
-    enable)
-        _enable
-        ;;
-    is-enabled)
-        _is-enabled
-        ;;
-    start)
-        _start
-        ;;
-    status)
-        _status
+    disable|enable|is-enabled|start|status|stop)
+
+        # Not for root
+        if [[ `id -u` -eq 0 ]]; then
+            exit 1
+        fi
+        _${1}
         ;;
-    stop)
-        _stop
+    ""|-h|--help)
+        _usage
         ;;
     *)
-        echo "Usage: $0 [disable|enable|is-enabled|start|status|stop]"
-        exit 1
+        _run "$@"
         ;;
 esac

tests/smoke.sh

@@ -46,6 +46,42 @@ run "$IMAGE" bash --login -c '
     set -o history; history -s ./slow; set +o history
     false; _help50
     test "$(cat /tmp/cmd)" = ./slow && test ! -s /tmp/output || exit 1
+
+    # A command run via help50 is reported as the command itself
+    : > "$HELP50"
+    set -o history; history -s "help50 ./slow"; set +o history
+    false; _help50
+    test "$(cat /tmp/cmd)" = ./slow || exit 1
+'
+
+echo "- help50 COMMAND runs COMMAND, with its exit status"
+run "$IMAGE" bash --login -c 'help50 true && ! help50 false && test "$(help50 echo x)" = x'
+run "$IMAGE" bash --login -c 'help50 valgrind python x.py < /dev/null; test $? -eq 1' 2>&1 | grep -q 'does not support Python'
+
+echo "- help50 COMMAND fails as COMMAND would have, so that helpers recognize the error"
+run "$IMAGE" bash --login -c 'out=$(help50 1s 2>&1); test $? -eq 127 && test "$out" = "bash: 1s: command not found"'
+run "$IMAGE" bash --login -c 'out=$(help50 --version 2>&1); test $? -eq 127 && test "$out" = "bash: --version: command not found"'
+run "$IMAGE" bash --login -c 'out=$(help50 cd nothere 2>&1); test $? -eq 1 && test "$out" = "bash: cd: nothere: No such file or directory"'
+run "$IMAGE" bash --login -c 'cd "$(mktemp -d)" && touch foo.c && out=$(help50 ./foo.c 2>&1); test $? -eq 126 && test "$out" = "bash: ./foo.c: Permission denied"'
+run "$IMAGE" bash --login -c 'cd "$(mktemp -d)" && mkdir foo && out=$(help50 ./foo 2>&1); test $? -eq 126 && test "$out" = "bash: ./foo: Is a directory"'
+
+echo "- help50 alone prints usage and exits 0"
+run "$IMAGE" bash --login -c 'help50 | grep -q "^Usage: help50 COMMAND" && help50 -h > /dev/null && help50 --help > /dev/null'
+
+echo "- root (as via sudo) may run help50 COMMAND but not its subcommands"
+run "$IMAGE" bash --login -c 'test "$(sudo help50 echo x)" = x && test -z "$(sudo help50 is-enabled 2>&1)"'
+
+echo "- within a help50 session, help50 COMMAND runs in the shell itself, so cd and aliases apply"
+run "$IMAGE" bash --login -c '
+    export HELP50=$(mktemp)
+    . /etc/profile.d/help50.sh
+    shopt -s expand_aliases
+    alias rm="echo aliased"
+    help50 cd /tmp && test "$PWD" = /tmp || exit 1
+    test "$(help50 rm x)" = "aliased x" || exit 1
+    help50 false; test $? -eq 1 || exit 1
+    out=$(help50 cd nothere 2>&1); test $? -eq 1 && [[ "$out" == *"cd: nothere: No such file or directory" ]] || exit 1
+    help50 is-enabled > /dev/null && test "$(help50 status)" = started || exit 1
 '
 
 echo "OK"