Re: [Boost-build] How do I write a rule to generate a single cpp from xml/xsl?

From: Vladimir Prus (ghost_at_[hidden])
Date: 2006-02-13 05:05:32

Hi Mark,

>   rule xml-sources-in ( sources * )
>   {
>     local xml-souces ;
>     ...
>     #  What's the best jammer way here to cull the .xml sources?
>     return $(xml-sources) ;
>   }
>   rule xlt-sources-in ( sources * )
>   {
>     local xlt-souces ;
>       ...
>     return $(xlt-sources) ;
>   }
>
>   rule gen-cpp ( targets * : sources * : properties * )
>   {
>     XML-SOURCES on $(targets) =  [ xml-sources-in $(sources) ] ;
>     XSLT-SOURCES on $(targets) = [ xslt-sources-in $(sources) ] ;
>     # Experts:  Is there a more direct jammer way to do the above that
> would # not require xml-sources-in and xslt-sources-in rules?
>     SP on $(targets) = " " ;
>   }

>   Use similar approach for generating HTM type.
>
>   Experts, did I miss anything?  Would you have discriminated  further
> upstream in the generator to automatically populate XML-SOURCES  and
> XSLT-SOURCES for the actions block and obviate the need for all the  noise
> above?  (I anticipate a YES answer to that.)

Looking at Daniel's original code, it seems that only a single pair of "xml" 
and "xslt" target is processed at once. And the only issue is how to make 
sure that sources comes in specific order, so that inside action you know 
that

   $(>[1]) 

is XML source, and

   $(>[2])

is XSL source. The only way I can think of is custom generator with the 
following 'generated-targets' rule:

    rule generated-targets ( sources + : property-set : project name ? )
    {
        local xml ;
        local xsl ;
        for local s in $(sources)
        {
            if [ $(s).type ] = XML
            {
                xml += $(s) ;
            }
        }
        for local s in $(sources)
        {
            if [ $(s).type ] = XSLT
            {
                xsl += $(s) ;
            }
        }

        return [ generator.generated-targets $(xml) $(xsl)
            : $(property-set) : $(project) $(name) ] ;
    }

Not extra nice, and not better than what you've proposed, but that's how I did 
it before. Maybe, we just need 'virtual-target.select-by-type' helper rule, 
so that above can be rewritten as:

    rule generated-targets ( sources + : property-set : project name ? )
    {
        return [ generator.generated-targets 
                    [ virtual-target.select-by-type XML : $(sources) ] 
                    [ virtual-target.select-by-type XSLT : $(sources) ] 
            : $(property-set) : $(project) $(name) ] ;
    }     

Mark, Daniel, what do you think?

For reference, my test code is attached.

- Volodya

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