FS#3683 - jsonfilter yields unreliable results

[openwrt-bot]

arnysch:

• Device is an Arcadyan VGV7510KW22 (o2 Box 6431)
• Box software version is OpenWrt 19.07-SNAPSHOT, r11318-c64742a96e
• Problem shows up in package wireguard_tool which provides script wireguard_watchdog" which uses jsonfilter.
• Short steps to reproduce:

• Use attached file jinp1 as input and run this command:
  jsonfilter -a -e '@[@.proto="wireguard"].interface' <jout1
  => nothing is output (empty output), which is incorrect

• Now use attached file jinp2, which is jinp1 with lines slighty reordered:
  jsonfilter -a -e '@[@.proto="wireguard"].interface' <jout2
  => "wgvpn" is output, which is correct, this time.

• Background: Script wireguard_watchdog tries to identify the WireGuard network interfaces.
  To this end it runs these commands:
  ubus -S call network.interface dump | jsonfilter -e '@.interface[@.up=true]' | jsonfilter -a -e '@[@.proto="wireguard"].interface'
  The second jsonfilter call in this line erroneously does not show a result.
  The attached files jinp1, jinp2 contain example input for the 2nd jsonfilter call

[openwrt-bot]

mikma:

The problem is caused by a bug in the array parsing. It can be solved with the following patch.

https://patchwork.ozlabs.org/project/openwrt/list/?series=244999