Using Template::Toolkit in Quattor components

In some cases, most of the code deals with printing correctly to a file, and it could be simplified a lot by using a basic template instead of zillions of print statements.

For instance, the accounts component could do the following to fully generate /etc/passwd:

# WARNING: UNTESTED!!!

use Template;
use CAF::FileWriter;

my $fh = CAF::FileWriter->new("/etc/passwd", log => $self);
my $tree = $config->getElementGetTree();
# This one is needed for Template::Toolkit to work with the CAF::File*
my $tpl = Template->new();
$tpl->process(\*DATA, $tree, $fh);
$fh->close();

__DATA__

[% FOREACH user in users.pairs %]
[% user.key %]:x:[% user,value.uid %]:[% user.value.gid %]:[% user.value.comment %]:[% user.value.homeDir %]:[% user.value.shell %]
[% END %]

The code would thus only choose what accounts are valid or invalid in the system.

The advantage in some sitiations is that the representation is completely isolated from the logic that will generate it. And it may allow for a closer correspondency with the schema, if wanted.

Sometimes one template won't be enough: there will be several files of several types to print (f.i, nagios-related configuration). We still have to see how to ship different templates.

Also, we have to be careful so that we don't replace ugly code with even uglier templates!!