[Puppet Users] Error: Function does not return a value

Any words/thoughts/suggestions/hints/ideas/pointers ?

Basically, it doesn't work because the Ruby block defining your function's
behavior (do |args| ... end) is exactly that -- a block. The 'return'
statement does not set the value of the block; instead, it attempts to
return from the method that evaluates the block. Without knowing any
details about that method's implementation, it is very dangerous to make
your block attempt to return from it. Indeed, it appears that doing so is
the wrong thing in this case.

You must instead ensure that the block evaluates to the desired value. For
example:

module Puppet::Parser::Functions
newfunction(:pattern_in_file, :type => :rvalue) do |args|
filename = args[0]
pattern = args[1]
File.open(filename) do |f|
f.lines.any? { |line| line.match(pattern) }
end or false
# The "or false" converts nil to false for safety, in
# the event that the specified file does not exist.
end
end


That's cleaner and clearer anyway, at least for this example.


John

Hi John,

Thanks for the reply. Your corrections made it work. As you pointed out
about the implementation of this code. I wrote it keeping in mind 'def' of
ruby where one can return a value evaluating a block. Syntactically it
didn't have a problem with Ruby, but it failed to return a value in
puppet's case.

I am trying to implement this code to check pattern in a file, e.g.
(/etc/fstab) before puppet tries to edit it. In other words, trying to find
an equivalent of "BeginGroupIfNoLineContaining" of cfengine. This may not
be the best method though.

Cheers

Not only is it not the best method, it is not a viable method. Puppet
functions are evaluated on the master, with no visibility on client details
other than anything passed as arguments. You need something that runs on
the client.

You might want to look into augeas for editing the file. Alternatively, it
would be closer to your current design to implement and use a custom fact.
If you are modifying the file via an Exec, then use grep in its 'onlyif' or
'unless' parameter. There are other alternatives, too.


John