On Nov 2, 11:43 am, Nigel Kersten <ni...@puppetlabs.com> wrote:
> On Tue, Nov 2, 2010 at 4:32 PM, Patrick <kc7...@gmail.com> wrote:
>
> > On Nov 2, 2010, at 9:14 AM, Michael Gliwinski wrote:
>
> >> On Tuesday 02 Nov 2010 15:06:19 Nigel Kersten wrote:
>
> >>> Thanks. There's one thing I'm not quite clear on.
>
> >>> This proposal means we have concatenation and find-first-existing
> >>> support for the source parameter, and concatenation for the template
> >>> function, but how are we proposing we provide find-first-existing
> >>> support for the template and file functions? Or are we dropping that
> >>> goal?
>
> >> I believe that was by either passing an array or multiple arguments, no?
> >> E.g.:
>
> >> find-first-existing:
>
> >> file('foo', 'bar')
> >> template('foo.erb', 'bar.erb')
>
> >> concatenation:
>
> >> concat(file('foo'), file('bar'))
> >> concat(template('foo.erb'), template('bar.erb'))
>
> >> that way you can even mix them ;)
>
> >> concat(file('header'), template("foo.$host.erb", "foo.erb"))
>
> > The proposal I was supporting (and the one in the bug tracker) retained
> > backward compatibility which means that passing more than one file to
> > template() still concatenates. That is deprecated though.
>
> > *) Would creating a function that says, 'return the first argument that
> > doesn't throw an exception' be useful?
> > *) Is it even feasible to write?
>
> maybe... I'm having trouble thinking of a decent name for this though :)
>
> > *) Also, I'm assuming that file() and template() throw an exception if the
> > file doesn't exist. Does anyone know if that's true?
>
> From memory they do, but I'll have to double check.
>
> > *) Also, what would you name this function?
>
> > I'm thinking that if we do take this approach, it should be split off into
> > another ticket.
>
> I kind of disagree with splitting it off.
>
> Perhaps I didn't express myself well, but my main impetus was to make
> the source/file/template data specifications *all* support the
> find-first-existing and concatenation functionality in a sane and
> consistent manner.
As Patrick already wrote, the proposal that seemed to garner broad
acceptance maintains backwards compatibility by preserving, but
deprecating, template()'s concatentation feature. If the function is
only supposed to be passed one argument, then the question of find-
first does not arise.
If there is a desire for find-first functionality for template(), then
I think the most general solution would be some version of Patrick's
suggested function for determining which file name to use, whether it
be named "coalesce", "first_file", "find_first", "first_existing",
"choose", "options", or something else. Thus:
template( find_first("t1", "t2") )
In that case, you might also consider deprecating multiple arguments
to the file() function in favor of this new approach (i.e.
file( find_first("foo", "bar") ) instead of file("foo", "bar") ).
Alternatively, a variant version of template() could be added that
provides find-first semantics. It could be named template_choose, or
some similar thing. I prefer the other approach, though.
John
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