What should be in the MVP?

[Ovid]

Per other discussions, it seems like P5P would prefer a specification rather than an implementation. That's what sort of happened with my initial work with Corinna, though Paul Evans then wrote Object::Pad and the community rallied around the idea to the point where Object::Pad is being used in production systems, despite the disclaimer that it shouldn't be.

We have three "main" components for Data::Checks

Native checks

HASH, INT, and so on. These are implemented.

User-defined checks.

check Grades :isa(NUM[0..4]);

# The values of the hash must remain unique...
check Bijective  :on(HASH)  ($new_value, %target)  {
                                         #######
    return $target{old} eq $new_value
           || not grep { $_ eq $new_value} } values $target{var}->%*;
}

This is not yet implemented.

Coercions

# Must be a string that's at least twelve characters long (if not, pad it)...
coercion LongStr  :to(STR[/.{12}/])  ($value) {
    my $is_ref = reftype($value);
    die "$is_ref reference $value can't be converted to a LongStr" if $is_ref;
    return sprintf('%12s', $value) }
}

This is not yet implemented. They present some issues. One of the biggest is that coercions cannot be disabled without breaking the code.

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I would suggest that for the MVP, we only include native checks. That will be a frustrating limitation, but also constrains the problem space. tremendously.