[Templates] format plugin can't work with TT list refs

[Stas Bekman]

Andy Wardley wrote:
> Stas Bekman wrote:
> 
>>  foo = [ 1 2 3 ];
>>  USE format_foo = format("%d %d %d");
>>  format_foo(foo);
> 
> 
> [...]
> 
> 
>>basically coercing the list ref into IV, instead of interpreting it as a 
>>list. Did I miss something obvious or is that a bug in that plugin?
> 
> 
> It's more of a limitation in the design.  TT treats all lists as list
> references and doesn't have a nice way to return the contents of the 
> list.  i.e. you can't do the Perl equivalent of @$listref.
> 
> The problem is in the stash.  Say you were to write a new list
> vmethod that returned the items in the list:
> 
>   $context->define_vmethod( list => items => sub { @$_[0] } );
> 
> You would expect to use it like so:
> 
>     format_foo(foo.items)    # doesn't work in TT2
> 
> However, when the stash calls the vmethod (in fact any method, or sub),
> it automatically folds a list of items into a reference to a list of 
> items.  foo.items returns a list, but format_foo() gets passed a list 
> ref.
> 
> I originally did this to support as many existing Perl modules that may
> return items.  In hindsight, it was a bad design decision.  It is useful
> but causes action-at-a-distance that probably catches more people out than
> it helps.  The documentation has long since said that returning a naked
> list of items (i.e. not a reference to a list) is frowned upon and may 
> not be supported in future versions.
> 
> TT3 is that future version.  As well as being able to write vmethods that
> return multiple items, as in the above example, I think I might also support
> '@' as a shortcut sigil.
> 
>     format_foo(foo.items)   # should work in TT3
>     format_foo(@foo)        # also work in TT3
> 
> I'm using '@' in the same way as '$' is used in TT, to indicate interpolation
> of a variable rather than being an indicator of the underlying data type, 
> as it is in Perl.  In TT is should be possible to put a '@' in front of 
> any variable.
> 
>     @hash     # same as hash.items    
>     @list     # same as list.items
>     @text     # same as text.items
> 
> In certain cases, these will be no-ops, as per the current .list .hash and
> .item vmethods that effectively cast one type to another.  

tt2++ => andy++

p.s. i suppose that tt3 will be out really soon now ;)

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Stas Bekman            JAm_pH ------> Just Another mod_perl Hacker
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