GNU bug report logs - #32920
Patch: Add variable json-pretty-print-max-indentation-level to allow more flexibility when pretty-printing json

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Jose Arroyo <jose.m.arroyo.se <at> gmail.com>
To: bug-gnu-emacs <at> gnu.org
Subject: Patch: Add variable json-pretty-print-max-indentation-level to allow
 more flexibility when pretty-printing json
Date: Wed, 3 Oct 2018 17:08:47 +0200

[Message part 1 (text/plain, inline)]

Hello everyone,

I came across a use-case when pretty-printing nested JSON objects. The
current
json-pretty-print function currently only supports unnesting and indenting
all
levels of nesting in a JSON object. I came across a case where I only
wanted to
unnest a single level.

I added a new variable (json-pretty-print-max-indentation-level) that
allows controlling
the number of unnests performed by json-pretty-print.

E.g:
(defun my/json-flatten-object-one-level (begin end)
  "(my/json-flatten-object-one-level BEGIN END) Pretty-print selected
region but only one level."
  (interactive "r")
  (let ((json-pretty-print-max-indentation-level 1))
    (json-pretty-print begin end)))

For example, if we have the following json
{"firstKey": {"46": "0"},"secondKey": {"46": [[[[0,0],0],0],0]},"thirdKey":
{"46": 0}}

The current json-pretty-print outputs:
{
  "firstKey": {
    "46": "0"
  },
  "secondKey": {
    "46": [
      [
        [
          [
            0,
            0
          ],
          0
        ],
        0
      ],
      0
    ]
  },
  "thirdKey": {
    "46": 0
  }
}

Whereas my/json-flatten-object-one-level would output:
{
  "firstKey": {"46": "0"},
  "secondKey": {"46": [[[[0,0],0],0],0]},
  "thirdKey": {"46": 0}
}

I've attached the patch for this, it's still missing the NEWS entries and
such.
However, I'm a noob in elisp and the current implementation feels kinda
wrong.
When json-pretty-print-max-indentation-level is set to 0, we ignore it by
decrementing it continously so we get into the negative numbers and the
check in
json--with-indentation "just works" because
json-pretty-print-max-indentation-level
is not 0. So given that it is now a negative number, it'll never be 0 again
(unless
there is a gigantic json that makes it overflow :p) so any number of nested
entities
are pretty-printed.

I imagine this is not good enough but I haven't figured out something
better.
Is there a better way to do this? Any pointers?

Thank you

José

PS: Would this kind of patch require me to sign some papers for
contributing?

[Message part 2 (text/html, inline)]

[0001-Add-new-variable-json-pretty-print-max-indentation-l.patch (application/octet-stream, attachment)]

Message #12 received at 32920 <at> debbugs.gnu.org (full text, mbox):

From: Lars Ingebrigtsen <larsi <at> gnus.org>
To: Jose Arroyo <jose.m.arroyo.se <at> gmail.com>
Cc: 32920 <at> debbugs.gnu.org
Subject: Re: bug#32920: Patch: Add variable
 json-pretty-print-max-indentation-level to allow more flexibility when
 pretty-printing json
Date: Sun, 23 Jun 2019 23:25:03 +0200

Jose Arroyo <jose.m.arroyo.se <at> gmail.com> writes:

> For example, if we have the following json
> {"firstKey": {"46": "0"},"secondKey": {"46": [[[[0,0],0],0],0]},"thirdKey":
> {"46": 0}}
>
> The current json-pretty-print outputs:
> {
>   "firstKey": {
>     "46": "0"
>   },
>   "secondKey": {
>     "46": [
>       [
>         [
>           [
>             0,
>             0
>           ],
>           0
>         ],
>         0
>       ],
>       0
>     ]
>   },
>   "thirdKey": {
>     "46": 0
>   }
> }

That is, indeed, really bad pretty printing of the arrays.  But I think
the approach you take in the patch isn't ideal, either: If you have
nested hash maps, then you want to have them nicely indented and broken
up into shapes like the one above.

> Whereas my/json-flatten-object-one-level would output:
> {
>   "firstKey": {"46": "0"},
>   "secondKey": {"46": [[[[0,0],0],0],0]},
>   "thirdKey": {"46": 0}
> }

I think a better solution here would be to just handle [] arrays in a
totally different way than the current pretty-printer, and instead keep
them on one line.  Well, at least more on one line than today...

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

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