From: Jim Weirich <jim@...>
Date: 2006-03-21T03:45:40+09:00
Subject: Re: rake rules with multiple prerequisites

Joel VanderWerf wrote:
> Jim Weirich wrote:
>>>
>> Remember, your rule says that you can build a site_XXX file if the 
>> following file (or rules to build the following files) exist: 
>> site_cfg_file(fn), "foo", "bar" and "baz".  I would check to see if 
>> "foo", "bar" and "baz" all exist.
> 
> Here's what happens in this example:

Oops.  Sorry, I misread your example.  I thought you were saying the 
first example with the [proc{"foo"} ... ] wasn't working.

As I understand, what you would like is:

   FileList["foo", ... ]

to work as well.

The problem is that a plain string in the *rule* dependency list already 
has a meaning: it is the file extension to be used in the name of the 
source file for the target.

> Furthermore, if I comment out the proc:
> 
> #  proc {|fn| "__#{fn}"},
> 
> (still using the FileList) then rake goes into a tailspin:
> 
> $ rake site_stuff --trace
> (in /home/vjoel/ruby/misc/rake)
> rake aborted!
> Rule Recursion Too Deep: [site_stuff => site_stuff => site_stuff =>
> site_stuff =.......

The reason for the tail spin is that plain strings in the depedency list 
for rules specifies file extensions.  Since "site_stuff" has no 
extension, it comes out unchanged in the dependency list.  So it looks 
like "site_stuff" depends on "site_stuff", which is an circular 
dependency.

You can do this:

generic_files = FileList["foo", "bar", "baz"].collect { |fn| lambda { fn 
} }

--
-- Jim Weirich

-- 
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