Pretty format GeoJSON Features

pretty-geojson.go

package main

import (
	"github.com/tidwall/gjson"
	"github.com/tidwall/pretty"
)

var json = []byte(`
{
  "type": "Feature",
  "geometry": {
    "type": "Polygon",
    "coordinates": [[[-67.13734351262877, 45.137451890638886],
       [-66.96466, 44.8097],
       [-68.03252, 44.3252],
       [-69.06, 43.98],
       [-70.11617, 43.68405],
       [-70.64573401557249, 43.090083319667144],
       [-70.75102474636725, 43.08003225358635],
       [-70.79761105007827, 43.21973948828747],
       [-70.98176001655037, 43.36789581966826],
       [-70.94416541205806, 43.46633942318431],
       [-71.08482, 45.3052400000002],
       [-70.6600225491012, 45.46022288673396],
       [-70.30495378282376, 45.914794623389355],
       [-70.00014034695016, 46.69317088478567],
       [-69.23708614772835, 47.44777598732787],
       [-68.90478084987546, 47.184794623394396],
       [-68.23430497910454, 47.35462921812177],
       [-67.79035274928509, 47.066248887716995],
       [-67.79141211614706, 45.702585354182816],
       [-67.13734351262877, 45.137451890638886]]]
  },
  "properties":{"key2": "hello","key1":"world"}
}
`)

func prettyGeoJSON(json []byte) []byte {
	// get the geometry.
	res := gjson.GetBytes(json, "geometry")

	// sanity checks
	if res.Index == 0 || len(res.Raw) == 0 ||
		res.Raw[0] != '{' || res.Raw[len(res.Raw)-1] != '}' {
		// probably a generic geometry, make it ugly
		return pretty.Ugly(json)
	}

	// make an ugly copy of just the geometry segment
	geom := pretty.Ugly(json[res.Index : res.Index+len(res.Raw)])

	// now for the tricky part.

	// empty the geometry object. 
	// Note that this mutates the original json.
	for i := 1; i < len(res.Raw)-1; i++ {
		json[res.Index+i] = ' '
	}

	// make the json pretty
	json = pretty.Pretty(json)

	// find the new location of the geometry
	res = gjson.GetBytes(json, "geometry")

	// allocate the space for the final json.
	final := make([]byte, len(json)+len(geom)-2)
	copy(final, json[:res.Index])
	copy(final[res.Index:], geom)
	copy(final[res.Index+len(geom):], json[res.Index+len(res.Raw):])

	return final
}

func main() {
	json = prettyGeoJSON(json)
	println(string(json))
}

Output will look like:

{
  "type": "Feature",
  "geometry": {"type":"Polygon","coordinates":[[[-67.13734351262877,45.137451890638886],[-66.96466,44.8097],[-68.03252,44.3252],[-69.06,43.98],[-70.11617,43.68405],[-70.64573401557249,43.090083319667144],[-70.75102474636725,43.08003225358635],[-70.79761105007827,43.21973948828747],[-70.98176001655037,43.36789581966826],[-70.94416541205806,43.46633942318431],[-71.08482,45.3052400000002],[-70.6600225491012,45.46022288673396],[-70.30495378282376,45.914794623389355],[-70.00014034695016,46.69317088478567],[-69.23708614772835,47.44777598732787],[-68.90478084987546,47.184794623394396],[-68.23430497910454,47.35462921812177],[-67.79035274928509,47.066248887716995],[-67.79141211614706,45.702585354182816],[-67.13734351262877,45.137451890638886]]]},
  "properties": {
    "key2": "hello",
    "key1": "world"
  }
}