anchors don't survive when files are included using the Include Schema

[djerius]

I'd like to use included yaml files to keep common configuration data. For example:

# db.yml
db : &db
  host : hostname
  port : 5432

And in the yaml files used by the applications,

# app1.yml
config : !include db.yml
args :
   db : *db

But (perhaps unsurprisingly) the anchor is not carried over from the included file:

my $include = YAML::PP::Schema::Include->new;
my $yp      = YAML::PP->new( schema => [ q{+}, 'Merge', $include ] );
$include->yp($yp);
p $yp->load_file('app1.yml');

Results in

No anchor defined for alias 'db' at .../YAML/PP/Parser.pm line 61.
 at .../YAML/PP/Loader.pm line 94.

I find that I use anchors quite a bit to avoid duplication, and the ability for them to exist across included file boundaries would be quite helpful.

[perlpunk]

That's definetely a use case I can imagine, and I've been thinking about it recently, since I saw a colleague trying to do something where this would have helped.
Bad news first: The Include plugin isn't designed to do this currently.
What it does: While parsing the main file, it sees the include. It will then start an (almost) completely new process of loading a YAML document from the included file and return it as a data struture.
The upper process takes this value as the value in place for that include entry. The anchors and aliases in the loaded data have already been processed at this time.
In retrospective a tag name !loadfile instead of !include might have been clearer ;-)

I can think of a different kind of include plugin, which I'd rather call "Inline" maybe, where from the perspective of the parser of the main YAML the referenced document would look like it was directly in the main file itself.
This way your use case should be possible. And possibly also the other way around - having the anchor defined in the main YAML and using the alias in the Inline, but it would have the disadvantage that the inlined file wouldn't be a really valid YAML file on its own).
I'm currently swamped with other tasks, though... But I hope I can look into this at some point.

[djerius]

Thanks for thinking about this. For now I've hacked my config loading code so that if it sees a + sign in the file name it knows it's two files that get concatenated before getting parsed, e.g. 'config.yaml+app1.yaml'. Crude, but it gets it out the door.