From 5a600375360829c82bc2f51aa758d3c761d1203e Mon Sep 17 00:00:00 2001
From: Ian Kelling <iank@fsf.org>
Date: Mon, 4 Nov 2019 15:58:02 -0500
Subject: [PATCH] use ruby style, support interactive shell

---
 err | 84 +++++++++++++++++++++++++++++++++++++++++++++++--------------
 1 file changed, 65 insertions(+), 19 deletions(-)

diff --git a/err b/err
index 73013a8..f6a7042 100644
--- a/err
+++ b/err
@@ -23,7 +23,7 @@
 #######################################
 # Print stack trace
 #
-# usage: err-bash-trace [FRAME_START]
+# usage: err-bash-trace [MESSAGE]
 #
 # This function is called by the other functions which print stack
 # traces.
@@ -32,28 +32,27 @@
 # shopt -s extdebug
 # which err-catch & err-print do for you.
 #
-# FRAME_START   The frame to start printing on. default=0. Useful when
-#               printing from an ERR trap function to avoid printing
-#               that function.
+# MESSAGE       Message to print just before the stack trace.
+#
+# _frame_start  Optional variable to set before calling. The frame to
+#               start printing on. default=1. Useful when printing from
+#               an ERR trap function to avoid printing that function.
 #######################################
 err-bash-trace() {
-  local -i argc_index=0 frame i start=${1:-0} max_indent=8 indent
+  local -i argc_index=0 frame i start=${_frame_start:-1}
   local source
-  local extdebug=false
-  if [[ $(shopt -p extdebug) == *-s* ]]; then
-    extdebug=true
+  if [[ $1 ]]; then
+    printf "%s\n" "$1"
   fi
-  for ((frame=0; frame < ${#FUNCNAME[@]}-1; frame++)); do
+  for ((frame=0; frame < ${#FUNCNAME[@]}; frame++)); do
     argc=${BASH_ARGC[frame]}
     argc_index+=$argc
     ((frame < start)) && continue
     if (( ${#BASH_SOURCE[@]} > 1 )); then
-      source="${BASH_SOURCE[frame+1]}:${BASH_LINENO[frame]}:"
+      source="${BASH_SOURCE[frame]}:${BASH_LINENO[frame-1]}:"
     fi
-    indent=$((frame-start + 1))
-    indent=$((indent < max_indent ? indent : max_indent))
-    printf "%${indent}s↳%sin \`%s" '' "$source" "${FUNCNAME[frame]}"
-    if $extdebug; then
+    printf "  from %sin \`%s" "$source" "${FUNCNAME[frame]}"
+    if shopt extdebug >/dev/null; then
       for ((i=argc_index-1; i >= argc_index-argc; i--)); do
         printf " %s" "${BASH_ARGV[i]}"
       done
@@ -75,18 +74,61 @@ err-catch() {
     err=$?
     exec >&2
     set +x
-    echo "${BASH_SOURCE[1]}:${BASH_LINENO[0]}: \`$BASH_COMMAND' returned $err"
-    err-bash-trace 2
+    local msg="${BASH_SOURCE[1]}:${BASH_LINENO[0]}: \`$BASH_COMMAND' returned $err"
+    if (( ${#FUNCNAME[@]} > 2 )); then
+      local _frame_start=2
+      err-bash-trace "$msg"
+    else
+      echo "$msg"
+    fi
     set -e # err trap does not work within an error trap
-    # note :-: makes this compatible with set -u. shellcheck doesn't understand.
+    # note :-: makes this compatible with set -u, assigns : if unset, but shellcheck
+    # doesn't understand that.
+    # shellcheck disable=SC2154
     "${_errcatch_cleanup[@]:-:}"
-    echo "$0: exiting with code $err"
+    echo "$0: exiting with status $err"
     exit $err
   }
   trap _err-trap ERR
   set -o pipefail
 }
 
+
+#######################################
+# For interactive shells: on error, print stack trace and return
+#
+# Globals:
+#   _err_func_last  Used internally.
+#   _err_catch_err  Used internally.
+#   _err_catch_i    Used internally.
+#
+# misc: All shellcheck disables for this function are false positives.
+#######################################
+# shellcheck disable=SC2120
+err-catch-interactive() {
+  # shellcheck disable=SC2034
+  declare -i _err_func_last=0
+  set -E; shopt -s extdebug
+  # shellcheck disable=SC2154
+  trap '_err_catch_err=$? _trap_bc="$BASH_COMMAND"
+  if (( ${#FUNCNAME[@]} > _err_func_last )); then
+    echo ERR: \`$_trap_bc'"\'"' returned $_err_catch_err
+  fi
+  _err_func_last=${#FUNCNAME[@]}
+  if (( _err_func_last )); then
+    printf "  from %s:%s:in \`%s" "${BASH_SOURCE[0]}" "$(declare -F "${FUNCNAME[0]}"|awk "{print \$2}")" "${FUNCNAME[0]}"
+    if shopt extdebug >/dev/null; then
+      for ((_err_catch_i=${BASH_ARGC[0]}-1; _err_catch_i >= 0; _err_catch_i--)); do
+        printf " %s" "${BASH_ARGV[_err_catch_i]}"
+      done
+    fi
+    echo '"\'"'
+    return $_err_catch_err
+  fi' ERR
+  set -o pipefail
+}
+
+
 #######################################
 # Undoes err-catch. turns off exit and stack trace on error.
 #######################################
@@ -147,4 +189,8 @@ err-exit() {
 }
 
 # We want this more often than not, so run it now.
-err-catch
+if [[ $- == *i* ]]; then
+  err-catch-interactive
+else
+  err-catch
+fi
-- 
2.25.1