`uniprop` and friends are buggy, inconsistent, and potentially replaceable

[ab5tract]

The Problem

Raku currently very lightly wraps internal NQP and VM operations for:

• getting Unicode properties (uniprop)
• getting Unicode names (uniname / uninames)
• matching the first-or-only character of a string to a property or a property/property category pair (unimatch)
• producing Unicode characters (uniparse)
• producing numerical values from Unicode numbers (unival)

As currently implemented, these routines -- methods and subs alike -- do not perform their functions as well as they could.

Issues

• uniprop will return 0 if the property provided is not found. This would be better served with a Failure or Exception, or at the very least an empty string so that the return type is consistent.

• 'Properties' and 'Property Categories' are served via the same mechanism, even though they are only interchangeable from category to property and not the other way around.

  "w".unimatch("Latin", "Script") ==> say() # True
  "w".unimatch("Script", "Latin") ==> say() # False
  
  "w".uniprop("Script") ==> say() # Latin
  "w".uniprop("Latin")  ==> say() # Latin
  "w".uniprop           ==> say() # Ll      

• All of the methods which take properties could fail at compile time when provided with known nonexistent properties (ie, not stored in a variable).

  • As of right now, there is zero feedback that the provided property is nonexistent. This was reported already [6 years ago](https://github.com/rakudo/rakudo/issues/1496).

• Properties are returned from NQP with spaces separating words, but only _ separated property names are accepted going the other direction.

  "e".uniprop("Block")              # "Basic Latin" 
  "e".uniprop("Basic Latin")    # 0
  "e".uniprop("Basic_Latin")  # "Basic Latin"

  use nqp;
  my $a = nqp::unipropcode("Basic Latin"),
  my $b = nqp::unipropcode("Basic_Latin"),
  $a, $b, $a == $b ==> say()  # (0 6 False)

• The current implementation is not [thread-safe](https://github.com/rakudo/rakudo/issues/4871). See also at [the MoarVM level](https://github.com/MoarVM/MoarVM/issues/1717).

• There are separate methods for "first character" (uniprop/uniname) versus "full string" (uniprops, uninames). It feels far too Perl-ish at this point to accept a multi-character string as an argument that only operates ona single character.

  • Wouldn't it be reasonable to except uniprops to return a comprehensive list of applicable properties for a single character? Currently there is no way (that I am aware of) to get such a comprehensive list.

• (Nit-level deficiency) smashedtogetherlowercase is an ugly (at worst) or a non-conformant (at best) naming scheme.

The solution

The instructions for problem-solving state I'm not meant to spend any space on this in the initial post.

So for now, I'll just mention that -- at the HLL level -- I think we could achieve all current functionality as well as much more out of even a single method that utilizes adverbs.

[lizmat]

Feels to me an implementation of desired functionality in module space, would be a first step?

[ab5tract]

Feels to me an implementation of desired functionality in module space, would be a first step?

Hmmm.. I'm not sure how successfully some of the issues can be addressed without NQP and/or VM changes.

But it's a good idea for ironing out the actual replacement Raku API nonetheless.