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A to-json that formats for a human — one value per line, two spaces of indent, a space either side of the colon — imported over the one you already have.

Version

0.1.1 zef:raku-community-modules

Depends

JSON::Fast

License

Artistic-2.0

Its own test suite

1 file, green

Checked

2026-09-15 against Raku++ 3.28.0 and Rakudo 2026.08

Where it lives

raku.land · source

Install it #

$ rakupp install JSON::Pretty

zef install JSON::Pretty writes the same store; either installer leaves the module usable by both engines.

What it is for #

JSON that a person is going to read — a config file the program writes back, a fixture checked into a repository, a dump while debugging — wants generous whitespace and one value per line, so that a diff shows the line that changed rather than the whole document. JSON that a program is going to read wants none of that.

This distribution is the first kind. It re-implements the encoder with a fixed layout and leaves decoding to JSON::Fast, which it passes straight through.

Formatted output #

use JSON::Pretty;

say to-json({ outer => [ 1, { inner => 'v' }, [ ] ] });
say to-json([1, 2]);
say to-json(42).raku;
say to-json('hi').raku;
say to-json(Any).raku;
say to-json({}).raku;
say to-json([]).raku;

say from-json('{"a":[1,2,{"b":null}]}')<a>[2]<b>.raku;

{
  "outer" : [
    1,
    {
      "inner" : "v"
    },
    [ ]
  ]
}
[
  1,
  2
]
"42"
"\"hi\""
"null"
"\{ }"
"[ ]"
Any

The shape is fixed: two spaces per level, one element per line, and a space either side of the key's colon — which is the layout the module exists to produce and the reason to reach for it rather than JSON::Fast's own :pretty. Note the two empty containers: they come out as [ ] and { }, with a space inside, which is valid JSON and will not match a byte comparison against any other encoder.

The one thing to know #

use JSON::Pretty; does not give you a new function. It replaces to-json with a different one that has a different signature, and every option you might reflexively pass is gone:

use JSON::Pretty;

say &to-json.name;
say &from-json.name;

say (try to-json({ a => 1 }, :sorted-keys)) // 'sorted-keys: refused';
say (try to-json({ a => 1 }, :!pretty))     // 'pretty: refused';

my $point = class { has $.x; has $.y }.new(x => 1, y => 2);
say (try to-json($point)) // 'an object: refused';

pretty-json
from-json
sorted-keys: refused
pretty: refused
an object: refused

There is no way to turn the formatting off, no :sorted-keys, and no :spacing. In a file that already says use JSON::Fast;, adding this module re-binds to-json underneath existing call sites, and they break at run time rather than at compile time.

The missing :sorted-keys is the one that bites hardest, because hash order is not reproducible: under Rakudo it is randomised per process, so the same data gives a different file on every run. That defeats the diffing this module exists to make possible. If the output has to be stable, sort the structure into an ordered form before encoding it, or use JSON::Fast's encoder with both :pretty and :sorted-keys and accept a slightly different layout.

The last line is the other limit: anything that is not a string, number, boolean, list or hash is refused outright. There is no hook and no trait — convert your objects to plain data yourself first.