r.colors.out: Add JSON support

[NishantBansal2003]

fixes: #3537
Use parson to add json output format support to the r.colors.out and r3.colors.out module.
The JSON output looks like as follows:

[
    {
        "value": 1,
        "rgb": "rgb(21, 5, 57)"
    },
    {
        "value": 2,
        "rgb": "rgb(143, 15, 140)"
    },
    {
        "value": 3,
        "rgb": "rgb(95, 225, 24)"
    },
    {
        "value": 4,
        "rgb": "rgb(18, 116, 26)"
    },
    {
        "value": 5,
        "rgb": "rgb(136, 220, 166)"
    },
    {
        "value": 6,
        "rgb": "rgb(250, 245, 99)"
    },
    {
        "value": 7,
        "rgb": "rgb(221, 176, 246)"
    },
    {
        "value": 8,
        "rgb": "rgb(236, 78, 1)"
    },
    {
        "value": 9,
        "rgb": "rgb(2, 197, 45)"
    },
    {
        "value": 10,
        "rgb": "rgb(17, 118, 29)"
    },
    {
        "value": 11,
        "rgb": "rgb(127, 210, 181)"
    },
    {
        "value": 12,
        "rgb": "rgb(129, 13, 6)"
    },
    {
        "value": 13,
        "rgb": "rgb(105, 239, 116)"
    },
    {
        "value": 14,
        "rgb": "rgb(242, 232, 152)"
    },
    {
        "value": 15,
        "rgb": "rgb(90, 161, 179)"
    },
    {
        "value": 16,
        "rgb": "rgb(55, 187, 209)"
    },
    {
        "value": 17,
        "rgb": "rgb(24, 9, 97)"
    },
    {
        "value": 18,
        "rgb": "rgb(127, 247, 104)"
    },
    {
        "value": 19,
        "rgb": "rgb(114, 10, 161)"
    },
    {
        "value": 20,
        "rgb": "rgb(8, 35, 6)"
    },
    {
        "value": 21,
        "rgb": "rgb(220, 204, 139)"
    },
    {
        "value": 22,
        "rgb": "rgb(160, 3, 70)"
    },
    {
        "value": 23,
        "rgb": "rgb(146, 169, 74)"
    },
    {
        "value": 24,
        "rgb": "rgb(202, 8, 65)"
    },
    {
        "value": 25,
        "rgb": "rgb(32, 45, 210)"
    },
    {
        "value": 26,
        "rgb": "rgb(33, 173, 31)"
    },
    {
        "value": 27,
        "rgb": "rgb(62, 132, 123)"
    },
    {
        "value": 28,
        "rgb": "rgb(34, 120, 179)"
    },
    {
        "value": 29,
        "rgb": "rgb(48, 38, 22)"
    },
    {
        "value": "nv",
        "rgb": "rgb(255, 255, 255)"
    },
    {
        "value": "default",
        "rgb": "rgb(255, 255, 255)"
    }
]

[echoix]

The style errors are mostly about file endings. Either run pre-commit locally or use ruff and black. Applying the suggested comment might not always work, as it's missing a final newline.

[NishantBansal2003]

Please re-trigger the CI...
cc: @echoix

[echoix]

Once we start having review comments, it's easier when there's no more force pushes, as it's hard to follow when the commit doesn't exist anymore.

[NishantBansal2003]

Once we start having review comments, it's easier when there's no more force pushes, as it's hard to follow when the commit doesn't exist anymore.

Apologies, I initially thought the previous change was causing issues and was not relevant. I will be more careful next time.

[echoix]

Once we start having review comments, it's easier when there's no more force pushes, as it's hard to follow when the commit doesn't exist anymore.

Apologies, I initially thought the previous change was causing issues and was not relevant. I will be more careful next time.

There's no review comments (from us) yet, so you're doing fine ;)

[echoix]

But take a look at the build failures already here. Are you able to debug them locally, by doing a build on your side and fixing them ?

[NishantBansal2003]

I'm not sure what is causing the error in the macOS and GNU build CI with gnu17 and c++17. I tried running everything locally on macOS, and it works fine. Could you assist me in troubleshooting this issue?

[echoix]

I've found one error line on the macOS one: 8905-8907:

https://github.com/OSGeo/grass/actions/runs/11455850645/job/31882348189#step:10:8906

prt_json.c:11:28: error: unused parameter 'fp' [-Werror,-Wunused-parameter]
   11 |                      FILE *fp, JSON_Array *root_array, int perc)
      |                            ^
1 error generated.

So maybe try locally with the same flags as the GNU standards check job, to ensure the unused parameters are triggered as errors so you see them

[echoix]

Also make sure that you have correctly cleaned locally to make sure you build everything to see the potential issues

[NishantBansal2003]

Also make sure that you have correctly cleaned locally to make sure you build everything to see the potential issues

Sure, thanks! Fixing the issues now...

[wenzeslaus]

@cwhite911 Can you give your opinion on representing the special values - default and nulls (nv) and on representing the color itself? rgb(...) looks good, but GRASS GIS currently reads #RRGGBB and RRR:GGG:BBB. We can add support for rgb(...), output more than one format, ...

[wenzeslaus]

...define the individual color output as "intersection between HTML/CSS formats and GRASS GIS supported formats" so now hex format, but possibly rgb(...) in the future. You would be be at loss parsing it manually, but it would work just fine for passing it to HTML-aware function or back to GRASS GIS.

[neteler]

run pre-commit locally

(for this, see https://github.com/OSGeo/grass/blob/main/doc/development/style_guide.md#using-pre-commit)

[NishantBansal2003]

Is there anything that needs to be addressed?
cc: @cwhite911

[cwhite911]

Hi @NishantBansal2003. Nice job working on this PR! I've added a few comments for some improvements and had a few questions as well.

Will you add HEX or any other color formats as outputs?

[NishantBansal2003]

Rebasing because I was getting some unrelated errors in the last CI run.

[NishantBansal2003]

Rebasing because I was getting some unrelated errors in the last CI run.

Hey @echoix could you retrigger the CI, need to check if the errors of last CI run was resolved or not, since it is working fine in my local.

[NishantBansal2003]

Rebasing because I was getting some unrelated errors in the last CI run.

Hey @echoix could you retrigger the CI, need to check if the errors of last CI run was resolved or not, since it is working fine in my local.

Looks like there's an issue in my code. Can you help me debug it?

[echoix]

I don't understand yet... What is bothering me is tests on linux, without Pytest, on seemingly unrelated modules are failing too.. Is there something on the C library side that collides or something? a header problem?

[echoix]

I think something changed for macOS, a new run on merging the repo's main branch to my fork ends up failing while it wasn't failing on the upstream repo. Our env cache clears once a week, probably on sundays.

[NishantBansal2003]

I think something changed for macOS, a new run on merging the repo's main branch to my fork ends up failing while it wasn't failing on the upstream repo. Our env cache clears once a week, probably on sundays.

Some pytest tests are also failing in unrelated modules (https://github.com/OSGeo/grass/actions/runs/11643760411/job/32442951891?pr=4555#step:12:7654), and the same pytest tests are also failing locally for me. I'm not sure why this issue is occurring; is there something I'm missing?

EDIT: Never mind, I fixed the pytest failure(in local), but I'm not sure why the pytest fails without the last commit.

[wenzeslaus]

...would it be possible for reviewers to discuss and agree on changes before submitting their requests? 🤔 This could save time and ensure that we’re all aligned on the final direction of the PR.

I'm afraid the platform to discuss it is here, and you are part of the discussion. I know it is hard to determine the tone of the comments in the discussion, so many thanks for your patience with this PR.

With 104 conversation comments and the code being in a good shape from the beginning, I would prefer to merge this soon. I will check once more and aim at approving review, but I will be happy if someone else is faster in doing that. We may want to wait for macOS CI to be fixed before actually merging this.

[petrasovaa]

I suggest to merge this as is because any further discussion here is getting confusing. If devs have some tweaks, I suggest to open a new PR. Thanks @NishantBansal2003 for your patience!

[NishantBansal2003]

Thank you, reviewers. I’ve gained valuable insights through this PR, and your feedback has been instrumental in my learning process. I apologise if my tone seemed off in any of our discussions or if I was overly opinionated or asked too many questions at times. I’ll work on improving in this regard and am committed to contributing further to the GRASS GIS community 🌍💚.

[wenzeslaus]

Thank you @NishantBansal2003! And thanks everyone for their opinionated opinions! :-)