Thursday, December 9, 2010

perl, tags, and vim : effective code browsing.

Adding a tags file to vim makes for an effective code browser for perl.

I've just started a new job, so I have a large new repository of perl code and modules to familiarize myself with. I've taken this as an opportunity to refresh my tag-fu in vim. After creating a tag file with ctags [exhuberant ctags], I can now jump around my whole perl repo from within my vim session.

The -t command-line flag to vim opens files by tag (module) name, e.g. vim -t My::Module::Name. Within a vim session, I jump to the definition of a function by hitting ctrl-] with the cursor over a usage of the function, even if that definition is another file! Ctrl-t and I'm back where I started.

Today I found the -q flag to ctags, which adds the fully qualified tag for package methods, e.g. My::Package::method_1, which aids with long package names and the ctrl-] key. FTW!
I have this set of ctag flags aliased as "ctagit":

ctags -f tags --recurse --totals \
--exclude=blib --exclude=.svn \
--exclude=.git --exclude='*~' \
--extra=q \
--languages=Perl \

In my .vimrc file, I defined the tags search path as ./tags, tags,~/code/tags ;, this will look for a tags file in the directory of a loaded file, then the current directory, and then a hardcoded path in my code area.

" [ .vimrc file ] " set tag search path: directory of current file, current working directory, hard-path set tags=./tags,tags,~/code/tags

More info on using tags in vim is available in :help tags. I've found the following commands useful.

ctrl-]jump to tag from under cursor
visual ctrl-] jump to tag from visual mode
:tag tagname jump to tag tagname
:stag tagname split screen and open tagname
:tags show the tag stack, '>' labels the current tag
:ctrl-t jump to [count] older entry in the tag stack
:[count]pop jump to [count] older entry in tag stack
:[count]tag jump to [count] newer entry in tag stack

To configure vim to treat ':' (colon) as part of the keyword to match Long::Module::Sub::Module package names, add it to the iskeyword setting. I have multiple perl filetype hooks stored in files in .vim/ftplugin/perl/. These filetype hooks are enabled with the filetype plugin on directive in my main .vimrc file.

" [ .vimrc file]
"enable loading the ftplugin directories
filetype plugin on
" [ .vim/ftplugin/perl/keyword_for_perl file]
" Append : to the list of keyword chars to allow completion on Module::Names
set iskeyword+=:

The same effect could be conjured directly in the .vimrc file via autocmd:

" append colon(:) to the iskeyword list for perl files, to enable Module::Name completion.
autocmd FileType perl set iskeyword+=:

My Configuration files are available in the spazm/config git repository on github.


Eduardo L. Francisco said...

Thanks for this post! Really helped me to improve my work!

Unknown said...

Thanks for the post too.
Hello Eduardo, good to see you here.