Json.lns of augeas leaves policy.json files in readable, but messy state

[MrStupnikov]

Originally this problem was reported by one of OpenStack operators : when he used TripleO to tune API policies for one of the services, he ended up having valid JSON file, which looked invalid from operator's perspective. After taking a second look at this issue we have figured out that this is cause by Json.lns. I want to kindly ask you to take a look at the following steps to reproduce and let us know if this is a cosmetic issue that could be fixed or a feature.

root@ubuntu:~# cat /tmp/policy.json
{
    "context_is_admin": "role:admin or role:load-balancer_admin",
    "admin_or_owner": "is_admin:True or project_id:%(project_id)s",

    "load-balancer:read": "rule:admin_or_owner",
    "load-balancer:read-global": "is_admin:True",
    "load-balancer:write": "rule:admin_or_owner",
    "load-balancer:read-quota": "rule:admin_or_owner",
    "load-balancer:read-quota-global": "is_admin:True",
    "load-balancer:write-quota": "is_admin:True"
}
root@ubuntu:~# augtool --version
augtool 1.14.1 <http://augeas.net/>
Copyright (C) 2007-2016 David Lutterkort
License LGPLv2+: GNU LGPL version 2.1 or later
                 <http://www.gnu.org/licenses/lgpl-2.1.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

Written by David Lutterkort
root@ubuntu:~# augtool
augtool> set /augeas/load/Json/lens Json.lns
augtool> set /augeas/load/Json/incl /tmp/policy.json
augtool> load
augtool> set /files/tmp/policy.json/dict/entry[last()+1] 'groups'
augtool> touch /files/tmp/policy.json/dict/entry[last()]/array
augtool> save
Saved 1 file(s)
augtool> quit
root@ubuntu:~# cat /tmp/policy.json
{
    "context_is_admin": "role:admin or role:load-balancer_admin",
    "admin_or_owner": "is_admin:True or project_id:%(project_id)s",

    "load-balancer:read": "rule:admin_or_owner",
    "load-balancer:read-global": "is_admin:True",
    "load-balancer:write": "rule:admin_or_owner",
    "load-balancer:read-quota": "rule:admin_or_owner",
    "load-balancer:read-quota-global": "is_admin:True",
    "load-balancer:write-quota": "is_admin:True"
,
"groups":[]}

[georgehansper]

In general, Augeas lenses create files which are syntactically correct for a given syntax (such as Json), they do not necessarily make them "pretty".

Part of the problem is that for many languages such as JSON, spaces are not significant. So when a new entry is created, the amount of space that can or should be inserted becomes arbitrary.

In this case, it may be possible to update the lens to produce a more readable output, though I expect the indentation would remain messy.

I find it odd that appending another entry after "groups" inserts the new entry directly between previous one and the }

> augtool --noload  --noautoload 
augtool> set /augeas/load/Json/lens Json.lns
augtool> set /augeas/load/Json/incl /tmp/policy.json
augtool> load-file /tmp/policy.json
augtool> set /files/tmp/policy.json/dict/entry[last()+1] 'extra1'
augtool> set /files/tmp/policy.json/dict/entry[.='extra1']/string 'hello'
augtool> set /files/tmp/policy.json/dict/entry[last()+1] 'extra2'
augtool> set /files/tmp/policy.json/dict/entry[.='extra2']/string 'world'
augtool> preview /files/tmp/policy.json/
{
    "context_is_admin": "role:admin or role:load-balancer_admin",
    "admin_or_owner": "is_admin:True or project_id:%(project_id)s",

    "load-balancer:read": "rule:admin_or_owner",
    "load-balancer:read-global": "is_admin:True",
    "load-balancer:write": "rule:admin_or_owner",
    "load-balancer:read-quota": "rule:admin_or_owner",
    "load-balancer:read-quota-global": "is_admin:True",
    "load-balancer:write-quota": "is_admin:True"
,
"extra1":"hello","extra2":"world"}augtool> 

There is definitely room for improvement here