Add JSON output support to channel programs

The changes piggyback JSON output support on top of channel programs 
(#6558).  This way the JSON output support is targeted to scripting 
use cases and is easily maintainable since it really only touches 
one function (zfs_do_channel_program()).

This patch ports Joyent's JSON nvlist library from illumos to enable 
easy JSON printing of channel program output nvlist.  To keep the 
delta small I also took advantage of the fact that printing in
zfs_do_channel_program() was almost always done before exiting 
the program.

Reviewed by: Matt Ahrens <mahrens@delphix.com>
Reviewed-by: Tony Hutter <hutter2@llnl.gov>
Reviewed-by: Richard Elling <Richard.Elling@RichardElling.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Alek Pinchuk <apinchuk@datto.com>
Closes #7281

cmd/zfs/zfs_main.c

@@ -27,6 +27,7 @@
  * Copyright (c) 2013 Steven Hartland.  All rights reserved.
  * Copyright 2016 Igor Kozhukhov <ikozhukhov@gmail.com>.
  * Copyright 2016 Nexenta Systems, Inc.
+ * Copyright (c) 2018 Datto Inc.
  */
 
 #include <assert.h>
@@ -358,7 +359,7 @@ get_usage(zfs_help_t idx)
 	case HELP_BOOKMARK:
 		return (gettext("\tbookmark <snapshot> <bookmark>\n"));
 	case HELP_CHANNEL_PROGRAM:
-		return (gettext("\tprogram [-n] [-t <instruction limit>] "
+		return (gettext("\tprogram [-jn] [-t <instruction limit>] "
 		    "[-m <memory limit (b)>] <pool> <program file> "
 		    "[lua args...]\n"));
 	case HELP_LOAD_KEY:
@@ -7220,11 +7221,11 @@ zfs_do_channel_program(int argc, char **argv)
 	nvlist_t *outnvl;
 	uint64_t instrlimit = ZCP_DEFAULT_INSTRLIMIT;
 	uint64_t memlimit = ZCP_DEFAULT_MEMLIMIT;
-	boolean_t sync_flag = B_TRUE;
+	boolean_t sync_flag = B_TRUE, json_output = B_FALSE;
 	zpool_handle_t *zhp;
 
 	/* check options */
-	while ((c = getopt(argc, argv, "nt:m:")) != -1) {
+	while ((c = getopt(argc, argv, "nt:m:j")) != -1) {
 		switch (c) {
 		case 't':
 		case 'm': {
@@ -7266,6 +7267,10 @@ zfs_do_channel_program(int argc, char **argv)
 			sync_flag = B_FALSE;
 			break;
 		}
+		case 'j': {
+			json_output = B_TRUE;
+			break;
+		}
 		case '?':
 			(void) fprintf(stderr, gettext("invalid option '%c'\n"),
 			    optopt);
@@ -7391,14 +7396,18 @@ zfs_do_channel_program(int argc, char **argv)
 		    gettext("Channel program execution failed:\n%s\n"),
 		    errstring);
 		if (ret == ETIME && instructions != 0)
-			(void) fprintf(stderr, "%llu Lua instructions\n",
+			(void) fprintf(stderr,
+			    gettext("%llu Lua instructions\n"),
 			    (u_longlong_t)instructions);
 	} else {
-		(void) printf("Channel program fully executed ");
+		if (json_output) {
-		if (nvlist_empty(outnvl)) {
+			(void) nvlist_print_json(stdout, outnvl);
-			(void) printf("with no return value.\n");
+		} else if (nvlist_empty(outnvl)) {
+			(void) fprintf(stdout, gettext("Channel program fully "
+			    "executed and did not produce output.\n"));
 		} else {
-			(void) printf("with return value:\n");
+			(void) fprintf(stdout, gettext("Channel program fully "
+			    "executed and produced output:\n"));
 			dump_nvlist(outnvl, 4);
 		}
 	}

configure.ac

@@ -205,6 +205,7 @@ AC_CONFIG_FILES([
 	tests/zfs-tests/tests/functional/cli_root/zfs_load-key/Makefile
 	tests/zfs-tests/tests/functional/cli_root/zfs/Makefile
 	tests/zfs-tests/tests/functional/cli_root/zfs_mount/Makefile
+	tests/zfs-tests/tests/functional/cli_root/zfs_program/Makefile
 	tests/zfs-tests/tests/functional/cli_root/zfs_promote/Makefile
 	tests/zfs-tests/tests/functional/cli_root/zfs_property/Makefile
 	tests/zfs-tests/tests/functional/cli_root/zfs_receive/Makefile

include/libnvpair.h

@@ -20,6 +20,7 @@
  */
 /*
  * Copyright (c) 2000, 2010, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2013, Joyent, Inc. All rights reserved.
  */
 
 #ifndef	_LIBNVPAIR_H
@@ -46,6 +47,7 @@ extern int nvpair_value_match_regex(nvpair_t *, int, char *, regex_t *,
     char **);
 
 extern void nvlist_print(FILE *, nvlist_t *);
+int nvlist_print_json(FILE *, nvlist_t *);
 extern void dump_nvlist(nvlist_t *, int);
 
 /*

lib/libnvpair/Makefile.am

@@ -18,6 +18,7 @@ lib_LTLIBRARIES = libnvpair.la
 
 USER_C = \
 	libnvpair.c \
+	libnvpair_json.c \
 	nvpair_alloc_system.c
 
 KERNEL_C = \

lib/libnvpair/libnvpair_json.c

@@ -0,0 +1,403 @@
+/*
+ * This file and its contents are supplied under the terms of the
+ * Common Development and Distribution License ("CDDL"), version 1.0.
+ * You may only use this file in accordance with the terms of version
+ * 1.0 of the CDDL.
+ *
+ * A full copy of the text of the CDDL should have accompanied this
+ * source.  A copy of the CDDL is also available via the Internet at
+ * http://www.illumos.org/license/CDDL.
+ */
+/*
+ * Copyright (c) 2014, Joyent, Inc.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <strings.h>
+#include <wchar.h>
+#include <sys/debug.h>
+
+#include "libnvpair.h"
+
+#define	FPRINTF(fp, ...)				\
+	do {						\
+		if (fprintf(fp, __VA_ARGS__) < 0)	\
+			return (-1);			\
+	} while (0)
+
+/*
+ * When formatting a string for JSON output we must escape certain characters,
+ * as described in RFC4627.  This applies to both member names and
+ * DATA_TYPE_STRING values.
+ *
+ * This function will only operate correctly if the following conditions are
+ * met:
+ *
+ *       1. The input String is encoded in the current locale.
+ *
+ *       2. The current locale includes the Basic Multilingual Plane (plane 0)
+ *          as defined in the Unicode standard.
+ *
+ * The output will be entirely 7-bit ASCII (as a subset of UTF-8) with all
+ * representable Unicode characters included in their escaped numeric form.
+ */
+static int
+nvlist_print_json_string(FILE *fp, const char *input)
+{
+	mbstate_t mbr;
+	wchar_t c;
+	size_t sz;
+
+	bzero(&mbr, sizeof (mbr));
+
+	FPRINTF(fp, "\"");
+	while ((sz = mbrtowc(&c, input, MB_CUR_MAX, &mbr)) > 0) {
+		switch (c) {
+		case '"':
+			FPRINTF(fp, "\\\"");
+			break;
+		case '\n':
+			FPRINTF(fp, "\\n");
+			break;
+		case '\r':
+			FPRINTF(fp, "\\r");
+			break;
+		case '\\':
+			FPRINTF(fp, "\\\\");
+			break;
+		case '\f':
+			FPRINTF(fp, "\\f");
+			break;
+		case '\t':
+			FPRINTF(fp, "\\t");
+			break;
+		case '\b':
+			FPRINTF(fp, "\\b");
+			break;
+		default:
+			if ((c >= 0x00 && c <= 0x1f) ||
+			    (c > 0x7f && c <= 0xffff)) {
+				/*
+				 * Render both Control Characters and Unicode
+				 * characters in the Basic Multilingual Plane
+				 * as JSON-escaped multibyte characters.
+				 */
+				FPRINTF(fp, "\\u%04x", (int)(0xffff & c));
+			} else if (c >= 0x20 && c <= 0x7f) {
+				/*
+				 * Render other 7-bit ASCII characters directly
+				 * and drop other, unrepresentable characters.
+				 */
+				FPRINTF(fp, "%c", (int)(0xff & c));
+			}
+			break;
+		}
+		input += sz;
+	}
+
+	if (sz == (size_t)-1 || sz == (size_t)-2) {
+		/*
+		 * We last read an invalid multibyte character sequence,
+		 * so return an error.
+		 */
+		return (-1);
+	}
+
+	FPRINTF(fp, "\"");
+	return (0);
+}
+
+/*
+ * Dump a JSON-formatted representation of an nvlist to the provided FILE *.
+ * This routine does not output any new-lines or additional whitespace other
+ * than that contained in strings, nor does it call fflush(3C).
+ */
+int
+nvlist_print_json(FILE *fp, nvlist_t *nvl)
+{
+	nvpair_t *curr;
+	boolean_t first = B_TRUE;
+
+	FPRINTF(fp, "{");
+
+	for (curr = nvlist_next_nvpair(nvl, NULL); curr;
+	    curr = nvlist_next_nvpair(nvl, curr)) {
+		data_type_t type = nvpair_type(curr);
+
+		if (!first)
+			FPRINTF(fp, ",");
+		else
+			first = B_FALSE;
+
+		if (nvlist_print_json_string(fp, nvpair_name(curr)) == -1)
+			return (-1);
+		FPRINTF(fp, ":");
+
+		switch (type) {
+		case DATA_TYPE_STRING: {
+			char *string = fnvpair_value_string(curr);
+			if (nvlist_print_json_string(fp, string) == -1)
+				return (-1);
+			break;
+		}
+
+		case DATA_TYPE_BOOLEAN: {
+			FPRINTF(fp, "true");
+			break;
+		}
+
+		case DATA_TYPE_BOOLEAN_VALUE: {
+			FPRINTF(fp, "%s", fnvpair_value_boolean_value(curr) ==
+			    B_TRUE ? "true" : "false");
+			break;
+		}
+
+		case DATA_TYPE_BYTE: {
+			FPRINTF(fp, "%hhu", fnvpair_value_byte(curr));
+			break;
+		}
+
+		case DATA_TYPE_INT8: {
+			FPRINTF(fp, "%hhd", fnvpair_value_int8(curr));
+			break;
+		}
+
+		case DATA_TYPE_UINT8: {
+			FPRINTF(fp, "%hhu", fnvpair_value_uint8(curr));
+			break;
+		}
+
+		case DATA_TYPE_INT16: {
+			FPRINTF(fp, "%hd", fnvpair_value_int16(curr));
+			break;
+		}
+
+		case DATA_TYPE_UINT16: {
+			FPRINTF(fp, "%hu", fnvpair_value_uint16(curr));
+			break;
+		}
+
+		case DATA_TYPE_INT32: {
+			FPRINTF(fp, "%d", fnvpair_value_int32(curr));
+			break;
+		}
+
+		case DATA_TYPE_UINT32: {
+			FPRINTF(fp, "%u", fnvpair_value_uint32(curr));
+			break;
+		}
+
+		case DATA_TYPE_INT64: {
+			FPRINTF(fp, "%lld",
+			    (long long)fnvpair_value_int64(curr));
+			break;
+		}
+
+		case DATA_TYPE_UINT64: {
+			FPRINTF(fp, "%llu",
+			    (unsigned long long)fnvpair_value_uint64(curr));
+			break;
+		}
+
+		case DATA_TYPE_HRTIME: {
+			hrtime_t val;
+			VERIFY0(nvpair_value_hrtime(curr, &val));
+			FPRINTF(fp, "%llu", (unsigned long long)val);
+			break;
+		}
+
+		case DATA_TYPE_DOUBLE: {
+			double val;
+			VERIFY0(nvpair_value_double(curr, &val));
+			FPRINTF(fp, "%f", val);
+			break;
+		}
+
+		case DATA_TYPE_NVLIST: {
+			if (nvlist_print_json(fp,
+			    fnvpair_value_nvlist(curr)) == -1)
+				return (-1);
+			break;
+		}
+
+		case DATA_TYPE_STRING_ARRAY: {
+			char **val;
+			uint_t valsz, i;
+			VERIFY0(nvpair_value_string_array(curr, &val, &valsz));
+			FPRINTF(fp, "[");
+			for (i = 0; i < valsz; i++) {
+				if (i > 0)
+					FPRINTF(fp, ",");
+				if (nvlist_print_json_string(fp, val[i]) == -1)
+					return (-1);
+			}
+			FPRINTF(fp, "]");
+			break;
+		}
+
+		case DATA_TYPE_NVLIST_ARRAY: {
+			nvlist_t **val;
+			uint_t valsz, i;
+			VERIFY0(nvpair_value_nvlist_array(curr, &val, &valsz));
+			FPRINTF(fp, "[");
+			for (i = 0; i < valsz; i++) {
+				if (i > 0)
+					FPRINTF(fp, ",");
+				if (nvlist_print_json(fp, val[i]) == -1)
+					return (-1);
+			}
+			FPRINTF(fp, "]");
+			break;
+		}
+
+		case DATA_TYPE_BOOLEAN_ARRAY: {
+			boolean_t *val;
+			uint_t valsz, i;
+			VERIFY0(nvpair_value_boolean_array(curr, &val, &valsz));
+			FPRINTF(fp, "[");
+			for (i = 0; i < valsz; i++) {
+				if (i > 0)
+					FPRINTF(fp, ",");
+				FPRINTF(fp, val[i] == B_TRUE ?
+				    "true" : "false");
+			}
+			FPRINTF(fp, "]");
+			break;
+		}
+
+		case DATA_TYPE_BYTE_ARRAY: {
+			uchar_t *val;
+			uint_t valsz, i;
+			VERIFY0(nvpair_value_byte_array(curr, &val, &valsz));
+			FPRINTF(fp, "[");
+			for (i = 0; i < valsz; i++) {
+				if (i > 0)
+					FPRINTF(fp, ",");
+				FPRINTF(fp, "%hhu", val[i]);
+			}
+			FPRINTF(fp, "]");
+			break;
+		}
+
+		case DATA_TYPE_UINT8_ARRAY: {
+			uint8_t *val;
+			uint_t valsz, i;
+			VERIFY0(nvpair_value_uint8_array(curr, &val, &valsz));
+			FPRINTF(fp, "[");
+			for (i = 0; i < valsz; i++) {
+				if (i > 0)
+					FPRINTF(fp, ",");
+				FPRINTF(fp, "%hhu", val[i]);
+			}
+			FPRINTF(fp, "]");
+			break;
+		}
+
+		case DATA_TYPE_INT8_ARRAY: {
+			int8_t *val;
+			uint_t valsz, i;
+			VERIFY0(nvpair_value_int8_array(curr, &val, &valsz));
+			FPRINTF(fp, "[");
+			for (i = 0; i < valsz; i++) {
+				if (i > 0)
+					FPRINTF(fp, ",");
+				FPRINTF(fp, "%hd", val[i]);
+			}
+			FPRINTF(fp, "]");
+			break;
+		}
+
+		case DATA_TYPE_UINT16_ARRAY: {
+			uint16_t *val;
+			uint_t valsz, i;
+			VERIFY0(nvpair_value_uint16_array(curr, &val, &valsz));
+			FPRINTF(fp, "[");
+			for (i = 0; i < valsz; i++) {
+				if (i > 0)
+					FPRINTF(fp, ",");
+				FPRINTF(fp, "%hu", val[i]);
+			}
+			FPRINTF(fp, "]");
+			break;
+		}
+
+		case DATA_TYPE_INT16_ARRAY: {
+			int16_t *val;
+			uint_t valsz, i;
+			VERIFY0(nvpair_value_int16_array(curr, &val, &valsz));
+			FPRINTF(fp, "[");
+			for (i = 0; i < valsz; i++) {
+				if (i > 0)
+					FPRINTF(fp, ",");
+				FPRINTF(fp, "%hd", val[i]);
+			}
+			FPRINTF(fp, "]");
+			break;
+		}
+
+		case DATA_TYPE_UINT32_ARRAY: {
+			uint32_t *val;
+			uint_t valsz, i;
+			VERIFY0(nvpair_value_uint32_array(curr, &val, &valsz));
+			FPRINTF(fp, "[");
+			for (i = 0; i < valsz; i++) {
+				if (i > 0)
+					FPRINTF(fp, ",");
+				FPRINTF(fp, "%u", val[i]);
+			}
+			FPRINTF(fp, "]");
+			break;
+		}
+
+		case DATA_TYPE_INT32_ARRAY: {
+			int32_t *val;
+			uint_t valsz, i;
+			VERIFY0(nvpair_value_int32_array(curr, &val, &valsz));
+			FPRINTF(fp, "[");
+			for (i = 0; i < valsz; i++) {
+				if (i > 0)
+					FPRINTF(fp, ",");
+				FPRINTF(fp, "%d", val[i]);
+			}
+			FPRINTF(fp, "]");
+			break;
+		}
+
+		case DATA_TYPE_UINT64_ARRAY: {
+			uint64_t *val;
+			uint_t valsz, i;
+			VERIFY0(nvpair_value_uint64_array(curr, &val, &valsz));
+			FPRINTF(fp, "[");
+			for (i = 0; i < valsz; i++) {
+				if (i > 0)
+					FPRINTF(fp, ",");
+				FPRINTF(fp, "%llu",
+				    (unsigned long long)val[i]);
+			}
+			FPRINTF(fp, "]");
+			break;
+		}
+
+		case DATA_TYPE_INT64_ARRAY: {
+			int64_t *val;
+			uint_t valsz, i;
+			VERIFY0(nvpair_value_int64_array(curr, &val, &valsz));
+			FPRINTF(fp, "[");
+			for (i = 0; i < valsz; i++) {
+				if (i > 0)
+					FPRINTF(fp, ",");
+				FPRINTF(fp, "%lld", (long long)val[i]);
+			}
+			FPRINTF(fp, "]");
+			break;
+		}
+
+		case DATA_TYPE_UNKNOWN:
+			return (-1);
+		}
+	}
+
+	FPRINTF(fp, "}");
+	return (0);
+}

man/man8/zfs-program.8

@@ -18,7 +18,7 @@
 .Nd executes ZFS channel programs
 .Sh SYNOPSIS
 .Cm "zfs program"
-.Op Fl n
+.Op Fl jn
 .Op Fl t Ar instruction-limit
 .Op Fl m Ar memory-limit
 .Ar pool
@@ -46,6 +46,10 @@ will be run on
 and any attempts to access or modify other pools will cause an error.
 .Sh OPTIONS
 .Bl -tag -width "-t"
+.It Fl j
+Display channel program output in JSON format. When this flag is specified and
+standard output is empty - channel program encountered an error. The details of
+such an error will be printed to standard error in plain text.
 .It Fl n
 Executes a read-only channel program, which runs faster.
 The program cannot change on-disk state by calling functions from the

man/man8/zfs.8

@@ -300,7 +300,7 @@
 .Ar snapshot Ar snapshot Ns | Ns Ar filesystem
 .Nm
 .Cm program
-.Op Fl n
+.Op Fl jn
 .Op Fl t Ar timeout
 .Op Fl m Ar memory_limit
 .Ar pool script
@@ -4264,7 +4264,7 @@ Display the path's inode change time as the first column of output.
 .It Xo
 .Nm
 .Cm program
-.Op Fl n
+.Op Fl jn
 .Op Fl t Ar timeout
 .Op Fl m Ar memory_limit
 .Ar pool script
@@ -4286,6 +4286,10 @@ For full documentation of the ZFS channel program interface, see the manual
 page for
 .Xr zfs-program 8 .
 .Bl -tag -width ""
+.It Fl j
+Display channel program output in JSON format. When this flag is specified and
+standard output is empty - channel program encountered an error. The details of
+such an error will be printed to standard error in plain text.
 .It Fl n
 Executes a read-only channel program, which runs faster.
 The program cannot change on-disk state by calling functions from

tests/runfiles/linux.run

@@ -177,6 +177,10 @@ tests = ['zfs_mount_001_pos', 'zfs_mount_002_pos', 'zfs_mount_003_pos',
     'zfs_mount_encrypted', 'zfs_mount_remount']
 tags = ['functional', 'cli_root', 'zfs_mount']
 
+[tests/functional/cli_root/zfs_program]
+tests = ['zfs_program_json']
+tags = ['functional', 'cli_root', 'zfs_program']
+
 [tests/functional/cli_root/zfs_promote]
 tests = ['zfs_promote_001_pos', 'zfs_promote_002_pos', 'zfs_promote_003_pos',
     'zfs_promote_004_pos', 'zfs_promote_005_pos', 'zfs_promote_006_neg',

tests/zfs-tests/tests/functional/cli_root/Makefile.am

@@ -16,6 +16,7 @@ SUBDIRS = \
 	zfs_inherit \
 	zfs_load-key \
 	zfs_mount \
+	zfs_program \
 	zfs_promote \
 	zfs_property \
 	zfs_receive \

tests/zfs-tests/tests/functional/cli_root/zfs_program/Makefile.am

@@ -0,0 +1,5 @@
+pkgdatadir = $(datadir)/@PACKAGE@/zfs-tests/tests/functional/cli_root/zfs_program
+dist_pkgdata_SCRIPTS = \
+	setup.ksh \
+	cleanup.ksh \
+	zfs_program_json.ksh

tests/zfs-tests/tests/functional/cli_root/zfs_program/cleanup.ksh

@@ -0,0 +1,30 @@
+#!/bin/ksh -p
+#
+# CDDL HEADER START
+#
+# The contents of this file are subject to the terms of the
+# Common Development and Distribution License (the "License").
+# You may not use this file except in compliance with the License.
+#
+# You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
+# or http://www.opensolaris.org/os/licensing.
+# See the License for the specific language governing permissions
+# and limitations under the License.
+#
+# When distributing Covered Code, include this CDDL HEADER in each
+# file and include the License file at usr/src/OPENSOLARIS.LICENSE.
+# If applicable, add the following below this CDDL HEADER, with the
+# fields enclosed by brackets "[]" replaced with your own identifying
+# information: Portions Copyright [yyyy] [name of copyright owner]
+#
+# CDDL HEADER END
+#
+
+#
+# Copyright 2007 Sun Microsystems, Inc.  All rights reserved.
+# Use is subject to license terms.
+#
+
+. $STF_SUITE/include/libtest.shlib
+
+default_cleanup

tests/zfs-tests/tests/functional/cli_root/zfs_program/setup.ksh

@@ -0,0 +1,32 @@
+#!/bin/ksh -p
+#
+# CDDL HEADER START
+#
+# The contents of this file are subject to the terms of the
+# Common Development and Distribution License (the "License").
+# You may not use this file except in compliance with the License.
+#
+# You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
+# or http://www.opensolaris.org/os/licensing.
+# See the License for the specific language governing permissions
+# and limitations under the License.
+#
+# When distributing Covered Code, include this CDDL HEADER in each
+# file and include the License file at usr/src/OPENSOLARIS.LICENSE.
+# If applicable, add the following below this CDDL HEADER, with the
+# fields enclosed by brackets "[]" replaced with your own identifying
+# information: Portions Copyright [yyyy] [name of copyright owner]
+#
+# CDDL HEADER END
+#
+
+#
+# Copyright 2007 Sun Microsystems, Inc.  All rights reserved.
+# Use is subject to license terms.
+#
+
+. $STF_SUITE/include/libtest.shlib
+
+DISK=${DISKS%% *}
+
+default_setup $DISK

tests/zfs-tests/tests/functional/cli_root/zfs_program/zfs_program_json.ksh

@@ -0,0 +1,132 @@
+#!/bin/ksh -p
+#
+# CDDL HEADER START
+#
+# This file and its contents are supplied under the terms of the
+# Common Development and Distribution License ("CDDL"), version 1.0.
+# You may only use this file in accordance with the terms of version
+# 1.0 of the CDDL.
+#
+# A full copy of the text of the CDDL should have accompanied this
+# source.  A copy is of the CDDL is also available via the Internet
+# at http://www.illumos.org/license/CDDL.
+#
+# CDDL HEADER END
+#
+
+#
+# Copyright (c) 2018 Datto Inc.
+#
+
+. $STF_SUITE/include/libtest.shlib
+
+#
+# DESCRIPTION:
+#
+# STRATEGY:
+#	1. Compare JSON output formatting for a channel program to template
+#	2. Using bad command line option (-Z) gives correct error output
+#
+
+verify_runnable "both"
+
+function cleanup
+{
+	log_must zfs destroy $TESTDS
+	return 0
+}
+log_onexit cleanup
+
+log_assert "Channel programs output valid JSON"
+
+TESTDS="$TESTPOOL/zcp-json"
+log_must zfs create $TESTDS
+
+TESTZCP="/$TESTDS/zfs_rlist.zcp"
+cat > "$TESTZCP" << EOF
+	succeeded = {}
+	failed = {}
+
+	function list_recursive(root, prop)
+		for child in zfs.list.children(root) do
+			list_recursive(child, prop)
+		end
+		val, src  = zfs.get_prop(root, prop)
+		if (val == nil) then
+			failed[root] = val
+		else
+			succeeded[root] = val
+		end
+	end
+
+	args = ...
+
+	argv = args["argv"]
+
+	list_recursive(argv[1], argv[2])
+
+	results = {}
+	results["succeeded"] = succeeded
+	results["failed"] = failed
+	return results
+EOF
+
+# 1. Compare JSON output formatting for a channel program to template
+typeset -a pos_cmds=("recordsize" "type")
+typeset -a pos_cmds_out=(
+"{
+    \"return\": {
+        \"failed\": {},
+        \"succeeded\": {
+            \"$TESTDS\": 131072
+        }
+    }
+}"
+"{
+    \"return\": {
+        \"failed\": {},
+        \"succeeded\": {
+            \"$TESTDS\": \"filesystem\"
+        }
+    }
+}")
+typeset -i cnt=0
+typeset cmd
+for cmd in ${pos_cmds[@]}; do
+	log_must zfs program $TESTPOOL $TESTZCP $TESTDS $cmd 2>&1
+	log_must zfs program $TESTPOOL -j $TESTZCP $TESTDS $cmd 2>&1
+	# json.tool is needed to guarantee consistent ordering of fields
+	# sed is needed to trim trailing space in CentOS 6's json.tool output
+	OUTPUT=$(zfs program $TESTPOOL -j $TESTZCP $TESTDS $cmd 2>&1 | python -m json.tool | sed 's/[[:space:]]*$//')
+	if [ "$OUTPUT" != "${pos_cmds_out[$cnt]}" ]; then
+		log_note "Got     :$OUTPUT"
+		log_note "Expected:${pos_cmds_out[$cnt]}"
+		log_fail "Unexpected channel program output";
+	fi
+	cnt=$((cnt + 1))
+done
+
+# 2. Using bad command line option (-Z) gives correct error output
+typeset -a neg_cmds=("-Z")
+typeset -a neg_cmds_out=(
+"invalid option 'Z'
+usage:
+	program [-jn] [-t <instruction limit>] [-m <memory limit (b)>] <pool> <program file> [lua args...]
+
+For the property list, run: zfs set|get
+
+For the delegated permission list, run: zfs allow|unallow")
+cnt=0
+for cmd in ${neg_cmds[@]}; do
+	log_mustnot zfs program $TESTPOOL $TESTZCP $TESTDS $cmd 2>&1
+	log_mustnot zfs program $TESTPOOL -j $TESTZCP $TESTDS $cmd 2>&1
+	OUTPUT=$(zfs program $TESTPOOL -j $TESTZCP $TESTDS $cmd 2>&1)
+	if [ "$OUTPUT" != "${neg_cmds_out[$cnt]}" ]; then
+		log_note "Got     :$OUTPUT"
+		log_note "Expected:${neg_cmds_out[$cnt]}"
+		log_fail "Unexpected channel program error output";
+	fi
+	cnt=$((cnt + 1))
+done
+
+log_pass "Channel programs output valid JSON"