[PATCH nft 1/1] tests: prettify JSON in test output and add helper

[Thomas Haller <thaller@redhat.com>]

- add helper script "json-pretty.sh" for prettify/format JSON.
  It uses either `jq` or a `python` fallback. In my tests, they
  produce the same output, but the output is not guaranteed to be
  stable. This is mainly for informational purpose.

- add a "json-diff-pretty.sh" which prettifies two JSON inputs and
  shows a diff of them.

- in "test-wrapper.sh", after the check for a .json-nft dump fails, also
  call "json-diff-pretty.sh" and write the output to "ruleset-diff.json.pretty".
  This is beside "ruleset-diff.json", which contains the original diff.

Signed-off-by: Thomas Haller <thaller@redhat.com>
---
 tests/shell/helpers/json-diff-pretty.sh | 17 +++++++++++++++++
 tests/shell/helpers/json-pretty.sh      | 17 +++++++++++++++++
 tests/shell/helpers/test-wrapper.sh     |  4 ++++
 3 files changed, 38 insertions(+)
 create mode 100755 tests/shell/helpers/json-diff-pretty.sh
 create mode 100755 tests/shell/helpers/json-pretty.sh

diff --git a/tests/shell/helpers/json-diff-pretty.sh b/tests/shell/helpers/json-diff-pretty.sh
new file mode 100755
index 000000000000..bebb7e8ed006
--- /dev/null
+++ b/tests/shell/helpers/json-diff-pretty.sh
@@ -0,0 +1,17 @@
+#!/bin/bash -e
+
+BASEDIR="$(dirname "$0")"
+
+[ $# -eq 2 ] || (echo "$0: expects two JSON files as arguments" ; exit 1)
+
+FILE1="$1"
+FILE2="$2"
+
+pretty()
+{
+	"$BASEDIR/json-pretty.sh" < "$1" 2>&1 || :
+}
+
+echo "Cmd: \"$0\" \"$FILE1\" \"$FILE2\""
+diff -u "$FILE1" "$FILE2" 2>&1 || :
+diff -u <(pretty "$FILE1") <(pretty "$FILE2") 2>&1 || :
diff --git a/tests/shell/helpers/json-pretty.sh b/tests/shell/helpers/json-pretty.sh
new file mode 100755
index 000000000000..0d6972b81e2f
--- /dev/null
+++ b/tests/shell/helpers/json-pretty.sh
@@ -0,0 +1,17 @@
+#!/bin/bash -e
+
+# WARNING: the output is not guaranteed to be stable.
+
+if command -v jq &>/dev/null ; then
+	# If we have, use `jq`
+	exec jq
+fi
+
+# Fallback to python.
+exec python -c '
+import json
+import sys
+
+parsed = json.load(sys.stdin)
+print(json.dumps(parsed, indent=2))
+'
diff --git a/tests/shell/helpers/test-wrapper.sh b/tests/shell/helpers/test-wrapper.sh
index 9e8e60581890..4ffc48184dd7 100755
--- a/tests/shell/helpers/test-wrapper.sh
+++ b/tests/shell/helpers/test-wrapper.sh
@@ -202,6 +202,10 @@ if [ "$rc_test" -ne 77 -a "$dump_written" != y ] ; then
 	fi
 	if [ "$NFT_TEST_HAVE_json" != n -a -f "$JDUMPFILE" ] ; then
 		if ! $DIFF -u "$JDUMPFILE" "$NFT_TEST_TESTTMPDIR/ruleset-after.json" &> "$NFT_TEST_TESTTMPDIR/ruleset-diff.json" ; then
+			"$NFT_TEST_BASEDIR/helpers/json-diff-pretty.sh" \
+				"$JDUMPFILE" \
+				"$NFT_TEST_TESTTMPDIR/ruleset-after.json" \
+				2>&1 > "$NFT_TEST_TESTTMPDIR/ruleset-diff.json.pretty"
 			show_file "$NFT_TEST_TESTTMPDIR/ruleset-diff.json" "Failed \`$DIFF -u \"$JDUMPFILE\" \"$NFT_TEST_TESTTMPDIR/ruleset-after.json\"\`" >> "$NFT_TEST_TESTTMPDIR/rc-failed-dump"
 			rc_dump=1
 		else
-- 
2.42.0