Julius Plenz – Blog

debugging a zsh completion function

There's a Perl module threads::shared. However, it won't show up as a completion match to the perldoc command. Why is that?, a colleague asked me. Now, that obviously is a quirk, so let's debug it.

We start at /usr/share/zsh/functions/Completion/Unix/_perldoc, where we find this:

_alternative \
    'modules:module: _perl_modules -tP' \
    'pods:base pod: _perl_basepods' \
    'files:module or .pod file:_files -g "*.(pod|pm)(-.)"' &&

So, go on to _perl_modules: It searches for paths where Perl would store modules and their documentation (line 85):

inc=( $( $perl -e 'print "@INC"' ) )

Then, they do some complicated globbing stuff on the directories (line 104), where a loop iterates over $inc and stores each element in $libdir:

new_pms=( $libdir/{[A-Z]*/***/,}*${~sufpat}~*blib* )

There's the catch: This globbing expression will only recurse into subdirectories that start with an uppercase letter. Lowercase modules on the highest level are okay, though. That's why threads appears (from threads.pm), but threads::shared doesn't (from threads/shared.pm).

The search for all modules that are missed this way will translate to the following Z-Shell command:

$ print -l ${^=$(perl -e 'print "@INC"')}/[a-z]*/***/*.pm(.N)

posted 2011-09-01 tagged zsh and perl