Pretty print nested list by inserting linebreaks and indentation

Question

Consider following command

Cases[ToBoxes[Block[{Identity}, Graph[{1 <-> 2, 2 <-> 3, 1 -> 3, 2 -> 1, 2 -> 3, 3 -> 1}, 
          EdgeWeight -> Identity /@ {{0, 0}, {0, 0}, {1, 0}, {0, 1}, {1, 0}, {0, 1}}]]],
      _GraphicsComplexBox, Infinity][[1, 2]]

with its output

{{Arrowheads[Medium], 
  Directive[Opacity[0.7], Hue[0.6, 0.7, 0.5]], {Arrowheads[0.], 
   ArrowBox[BezierCurveBox[{1, {0.606341, 0.514848}, 2}], 0.0127299]},
   ArrowBox[BezierCurveBox[{1, {0.10576, 0.352183}, 3}], 0.0127299], 
  ArrowBox[BezierCurveBox[{2, {0.499413, 0.70158}, 3}], 
   0.0127299], {Arrowheads[0.], 
   ArrowBox[BezierCurveBox[{2, {0.500581, 1.03046}, 3}], 0.0127299]}, 
  ArrowBox[BezierCurveBox[{2, {0.890575, 0.349397}, 1}], 0.0127299], 
  ArrowBox[BezierCurveBox[{3, {0.391162, 0.515612}, 1}], 
   0.0127299]}, {Directive[Hue[0.6, 0.2, 0.8], 
   EdgeForm[Directive[GrayLevel[0], Opacity[0.7]]]], 
  DiskBox[1, 0.0127299], DiskBox[2, 0.0127299], 
  DiskBox[3, 0.0127299]}}

I would like to reformat the output to something like

{
    {
        Arrowheads[Medium],
        Directive[Opacity[0.7],
        Hue[0.6, 0.7, 0.5]],
        {
            Arrowheads[0.],
            ArrowBox[BezierCurveBox[{1, {0.606341, 0.514848}, 2}], 0.0127299]
        },
        ArrowBox[BezierCurveBox[{1, {0.10576, 0.352183}, 3}], 0.0127299], 
        ArrowBox[BezierCurveBox[{2, {0.499413, 0.70158}, 3}], 0.0127299],
        {
            Arrowheads[0.], 
            ArrowBox[BezierCurveBox[{2, {0.500581, 1.03046}, 3}], 0.0127299]
        }, 
        ArrowBox[BezierCurveBox[{2, {0.890575, 0.349397}, 1}], 0.0127299], 
        ArrowBox[BezierCurveBox[{3, {0.391162, 0.515612}, 1}], 0.0127299]
    },
    {
        Directive[Hue[0.6, 0.2, 0.8],
        EdgeForm[Directive[GrayLevel[0], Opacity[0.7]]]], 
        DiskBox[1, 0.0127299],
        DiskBox[2, 0.0127299], 
        DiskBox[3, 0.0127299]
    }
}

(ideally short lists are not broken)

Is there a way to do it in Mathematica or on the command line similar to GNU Indent or other available tools for languages like json, lisp, python list, etc. such as https://prettier.io ?

Answer 1

PrettyForm from <<GeneralUtilities

(applying comment of Kuba to given sample)

Cases[ToBoxes[Block[{Identity}, Graph[{1 <-> 2, 2 <-> 3, 1 -> 3, 2 -> 1, 2 -> 3, 3 -> 1}, 
          EdgeWeight -> Identity /@ {{0, 0}, {0, 0}, {1, 0}, {0, 1}, {1, 0}, {0, 1}}]]],
      _GraphicsComplexBox, Infinity][[1, 2]]

<< GeneralUtilities`; PrettyForm@%

This gives

{
    {
        Arrowheads @ Medium,
        Directive[Opacity @ 0.7, Hue[0.6, 0.7, 0.5]],
        {
            Arrowheads @ 0.,
            ArrowBox[
                    BezierCurveBox @ {1, {0.6063408473035717, 0.5148479095999602}, 2},
                    0.012729919145102353
                ]
        },
        ArrowBox[
            BezierCurveBox @ {1, {0.1057602447225488, 0.3521832484933547}, 3},
            0.012729919145102353
        ],
        ArrowBox[
            BezierCurveBox @ {2, {0.49941304589520347, 0.7015802720433176}, 3},
            0.012729919145102353
        ],
        {
            Arrowheads @ 0.,
            ArrowBox[
                    BezierCurveBox @ {2, {0.5005806025810231, 1.0304596775108001}, 3},
                    0.012729919145102353
                ]
        },
        ArrowBox[
            BezierCurveBox @ {2, {0.8905750124163706, 0.3493970235499975}, 1},
            0.012729919145102353
        ],
        ArrowBox[
            BezierCurveBox @ {3, {0.3911619665211691, 0.5156117679108979}, 1},
            0.012729919145102353
        ]
    },
    {
        Directive[Hue[0.6, 0.2, 0.8],
            EdgeForm @ Directive[GrayLevel @ 0, Opacity @ 0.7]
        ],
        DiskBox[1, 0.012729919145102353],
        DiskBox[2, 0.012729919145102353],
        DiskBox[3, 0.012729919145102353]
    }
 }

As you can see this

• breaks functions in general not only list constructs {} and
• represents floats in double precision.

Therefore the output is longer and not as compact as I hoped for.

BTW it also inserts prefix notation @ and possibly in other situations more shorthands.