Question

Why do I get this error, when I use the pretty print version?

‘”‘ expected, at character offset 2 (before “(end of string)”) at ./perl.pl line 29.

#!/usr/bin/env perl
use warnings;
use 5.014;
use utf8;
binmode STDOUT, ':encoding(utf-8)';
use Data::Dumper;
use JSON;

my $json = JSON->new->utf8;
my $hashref = { 
    'muster, hanß' => { 
        'hello' => { 
            year => 2000, 
            color => 'green' 
        }
    } 
};

my $utf8_encoded_json_text = $json->pretty->encode( $hashref ); # leads to a die
#my $utf8_encoded_json_text = $json->encode( $hashref ); # works

open my $fh, '>', 'testfile.json' or die $!;
print $fh $utf8_encoded_json_text;
close $fh;

open $fh, '<', 'testfile.json' or die $!;
$utf8_encoded_json_text = readline $fh;
close $fh;
$hashref = decode_json( $utf8_encoded_json_text );
say Dumper $hashref;

Answer 1

Because when you read the file back in, you’re using readline, and only reading the first line of the file. When pretty is off, the entire output is on one line. When pretty is on, the JSON is spread out over multiple lines, so you’re passing invalid truncated JSON to decode_json.

Read the entire content by using local $/ = undef; or slurp or whatever else you want.