Every time someone says they want to preserve the order of JSON keys, people jump on them for it, saying the keys are unordered by definition and why should they want that anyway? There are use cases for this!! Take the example of a JSON configuration file that happens to be stored in a git repository. Suppose you want to modify the JSON programmatically to make a slight change. If the keys are kept in the original order, a "git diff" of the changes will show a tiny change clearly. If all the hash keys are in a new randomized order, the diff will be mostly noise and the change will be very difficult to find.

Anyway, I came up with a good solution for this using Monkey::Patch with JSON::PP to make it use Tie::IxHash for all objects decoded from JSON. This solves the problem, allowing a JSON file to be loaded, decoded from JSON, modified, encoded into JSON again and written back to the file, without changing the key ordering at all. Just make sure you're using JSON::PP (not JSON::XS) and that the $handle variable remains in scope:

use Monkey::Patch qw[patch_package];

# Monkey-patch JSON::PP::object() subroutine to use Tie::IxHash.
my $handle = patch_package 'JSON::PP' => 'object' => sub {
  my $orig = shift;
  my %obj;
  tie %obj, 'Tie::IxHash'
    or die "tie(\%obj, 'Tie::IxHash') failed!\n";
  $orig->(\%obj)
};

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In reply to Re^2: Preserve the order in JSON by Deven
in thread Preserve the order in JSON by user786

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