Data::Resolver alternatives yield... alternatives


Fixing a design decision in Data::Resolver.

Data::Resolver provides both a unified interface to resolve keys to data (available as file, filehandle, or in-memory), as well as a few concrete implementations to do this on the filesystem and with TAR files.

It also supports a kind of meta-source that allows wrapping a few alternatives; this comes handy if multiple files and/or directories have to be searched during the resolution process. Like when a configuration file might be in your home directory, or in /etc, or in some application-specific place…

The generic interface supports pivoting to sub-resolvers. These are basically objects that support the same resolution process as anything else, only they provide a sub-view out of an outer element.

The joys of writing. As I wrote the above paragraph, I thought that this might be implemented in a very generic way. We’ll see.

My initial implementation would extract a sub-resolver from alternatives by just finding the first sub-item that would provide an answer. This, though, sort of defies the goal of representing multiple alternatives, especially when we’re not dealing with resolving one single key, but getting sub-resolvers. So here we go:

sub get_sub_resolver ($self, $key) {
   my @subs =
      map  { $_->get_sub_resolver($key) }
      grep { $_->has_sub_resolver($key) }
   $self->not_found($key) unless @subs;
   return ref($self)->new(alternatives => \@subs);

I guess this is part of the design process and how much time one can allocate. The 20/20 hindsight can be depressing at times, though.

Stay safe!

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