long-awaited sub::exporter features draw near

Since the very, very early days of Sub::Exporter, it was clear that it would be really useful to be able to replace the way that exporting itself occurs. That is: the way that routines are generated and installed, based on configuration, gathered collections, and other user arguments to the generated import method.

In the past, it was possible to replace this, but only by relying on an (intentionally) awful and undocumented interface. The routine worked something like this:

  1. build an arrayref of (thing, import-as) pairs
  2. call _do_import on each one
  3. _do_import cleans up the pair and some associated configuration
  4. _do_import calls the “exporter”
  5. the default exporter calls _generate to build the installable routine
  6. the default exporter calls _install to install the routine
  7. next pair

The “exporter” is the thing that was supposed to be pluggable. In fact, Sub::Exporter::Util contains an alternate exporter. The problem was that the interface stank, and I didn’t want to publish an interface until I had one I liked… but the possible uses are huge. I use it in the Sub::Exporter test suite to test what would have been done, basically letting me instrument the system. Dieter and I were talking about making a way to gather information about what has exported where for a kind of cheap metadata about what roles have been built where, and how. (This would be needed as part of my long-standing mixin factory idea, and as part of the roles stuff Dieter wants to work on.)

Finally, spurred on by outside demand (that is, Dieter), I made a first pass at implementation last night. I think it’s pretty good!


  1. build an arrayref of (thing, import-as) pairs
  2. call _do_import on arrayref
  3. _do_import calls the generator for each pair, generating a new arrayref
  4. _do_import the exporter, passing the new arrayref and some other info
  5. the default exporter installs the routine
  6. next pair

Now there are two publicly defined callbacks that can be provided, either for your whole exporting package (passed as part of the -setup for Sub::Exporter) or per call to import, as part of the optional initial hashref.

I’m hoping to see and create some fun new behaviors.

This code is on the CPAN as Sub::Exporter 0.977_01. It’s a big step toward 1.000.

Written on November 1, 2007
perl   programming