dwatch(1): Add `-dev' option to aid debugging of profiles

The options `-d' (debug), `-e' (exit after compile), and `-v' (verbose)
when combined in any order (though best remembered as `-dev') will run
the conflated script through dtrace(1), test for error conditions, and
show the line that dtrace(1) failed at (with context).

If no errors are found, the output is the same as `-e[v]'.

When writing a new profile for dwatch(1), you can quickly test to
make sure it compiles by running `dwatch -devX profile_name' where
profiles live in /usr/libexec/dwatch or /usr/local/libexec/dwatch
(the latter being where profiles installed via ports should go).

Sponsored by:	Smule, Inc.

cddl/usr.sbin/dwatch/dwatch

@@ -47,7 +47,7 @@ DTRACE_PRAGMA="
 
 ############################################################ GLOBALS
 
-VERSION='$Version: 1.0 $' # -V
+VERSION='$Version: 1.1 $' # -V
 
 pgm="${0##*/}" # Program basename
 
@@ -67,6 +67,7 @@ CUSTOM_DETAILS=		# -E code
 CUSTOM_TEST=		# -t test
 DEBUG=			# -d
 DESTRUCTIVE_ACTIONS=	# -w
+DEVELOPER=		# -dev
 EXECNAME=		# -k name
 EXECREGEX=		# -z regex
 EXIT_AFTER_COMPILE=	# -e
@@ -834,6 +835,11 @@ if [ "$PROBE_ARG" ]; then
 	IFS="$oldIFS"
 fi
 
+#
+# Developer switch
+#
+[ "$DEBUG" -a "$EXIT_AFTER_COMPILE" -a "$VERBOSE" ] && DEVELOPER=1 DEBUG=
+
 #
 # Set default event details if `-E code' was not given
 #
@@ -966,6 +972,61 @@ PSARGS_ACTION=$( cat <&9 )
 	exec 3>&1
 	console_stdout=3
 
+	#
+	# Developer debugging aide
+	#
+	if [ "$DEVELOPER" ]; then
+		#
+		# Run, capture the error line, and focus it
+		#
+		# Example error text to capture line number from:
+		# 	dtrace: failed to compile script /dev/stdin: line 669: ...
+		#
+		errline=
+		stdin_buf=$( cat )
+		stderr_buf=$( echo "$stdin_buf" |
+			dtrace_cmd -t -es /dev/stdin "$@" 2>&1 > /dev/null )
+		status=$?
+		if [ "$stderr_buf" ]; then
+			errline=$( echo "$stderr_buf" | awk '
+				BEGIN {
+					ti = "\033[31m"
+					te = "\033[39m"
+				}
+				{ line = $0 }
+				sub(/.*: line /, "") && sub(/:.*/, "") {
+					print # to errline
+					sub("line " $0, ti "&" te, line)
+				}
+				{ print line > "/dev/stderr" }
+			' 2>&3 )
+		fi
+		if  [ "$errline" ]; then
+			echo "$stdin_buf" | awk -v line="${errline%%[^0-9]*}" '
+				BEGIN {
+					start = line < 10 ? 1 : line - 10
+					end = line + 10
+					slen = length(sprintf("%u", start))
+					elen = length(sprintf("%u", end))
+					N = elen > slen ? elen : slen
+					for (i = start; i <= end; i++) {
+						ti[i] = "\033[2m"
+						te[i] = "\033[22m"
+					}
+					ti[line] = "\033[31m"
+					te[line] = "\033[39m"
+					fmt = "%s%*u %s%s\n"
+				}
+				NR < start { next }
+				NR == start, NR == end {
+					printf(fmt, ti[NR], N, NR, $0, te[NR])
+				}
+				NR > end { exit }
+			' # END-QUOTE
+		fi
+		exit $status
+	fi
+
 	if [ $COUNT -eq 0 -a ! "$EXECREGEX$FILTER$GROUP$OUTPUT_CMD$PID$USER" ]
 	then
 		case "$OUTPUT" in
@@ -1285,6 +1346,7 @@ $(	pproc_dump -v 3
 )}
 }
 EOF
+# NOTREACHED
 
 ################################################################################
 # END