Use structure in TO_JSON method when available

[dannymk]

Perhaphs add a sub that takes an instance that can actually return a structure that only includes items that we want in the output:

multi sub to-json ( $_ where *.can('TO_JSON') ) {
    to-json .TO_JSON
}

see: https://stackoverflow.com/questions/53110521/perl6-class-to-json-exclude-properties/53120677#53120677

[moritz]

Is there any consensus among the various Perl 6 JSON modules as to calling such a method, and if yes, how to call it?

Personally, I'd prefer AS-JSON, as TO implies a mutation of the invocant.

[dannymk]

In some of the Perl5 modules the documentation reads: "If $enable is true (or missing), then encode, upon encountering a blessed object, will check for the availability of the TO_JSON method on the object's class. If found, it will be called in scalar context and the resulting scalar will be encoded instead of the object."

[dannymk]

@moritz are you planning on incorporating the above patch into the module?

[moritz]

@dannymk not before there is any consensus with, or at least data from, other Perl 6 JSON modules

[dannymk]

Where are we supposed to get this consensus from?

[moritz]

From the authors of the other JSON-related p6 modules

[drforr]

Not speaking as an author of a JSON module here, but certainly of some other Perl 6 modules. Rather than hard-coding a method name, I'd suggest something like .to-json( $obj, :filter('method-name') ) or using a dynamic variable... $*JSON-FILTER-NAME='method-name'; $foo.to-json( $obj ); Both of those methods leave the choice of the filtering method to the user, and the dynamic variable means that you don't even need a 'multi method' variant.

[drforr]

Another suggestion that feels even more Perl6ish to me would be something like this:

class MyObject {
  has $.attribute;
  method JSON returns JSONStr { # your package could create this JSONStr subtype, optional
    as-json( self, { #`{ Your filter code here } } );
  }
}
# code passes...
my $obj = MyObject.new( :attribute("hello") );
status_ok( $obj.JSON ); # Return JSONified output, just like you'd say $obj.Str to stringify it.