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From Upayavira>
Subject [DONE] Nested variable resolving
Date Fri, 02 Apr 2004 20:22:33 GMT
I've just finished my nesting PreparedVariableResolver, along with some 
test cases. After getting the test cases to work, the Cocoon samples 
seem to work fine, without any modification!!! Wow! [I guess I'm used to 
breaking things when I change them. Unit tests seem like a great way to 
stop me from doing that!]

Anyway, I've committed it over the top of the existing implementation, 
which is what was discussed on this list.

The change should be transparent as far as existing sitemaps are 
concerned, even though it is a total rewrite. Only difference should be 
that you can nest now.

If poss, can you check out the test case - make sure I've got 
everything. I think I did.

Finally, the dispose method isn't called by the ExcaliburTestCase, so I 
haven't debugged it. Can someone who knows Avalon stuff check that my 
code looks alright within dispose()?

                                              - o -

This code does make some interesting things possible, including some 
nasty, and potentially dangerous, hacks. To explain what it does:

Here's a rough take on the parsing rules, roughly based on the Yacc  syntax:

expr: text                       {result = new expr(text) }
expr: { text : expr }        {result = evalModule( text, expr) }
expr: {text}                   {result = evalVariable(text) }
expr: expr expr              {result = expr + expr }

What you can see here is that,  anything immediately following an open 
bracket, must be text - it cannot be an expression. So you cannot do 
{{2}}. To achieve that, you'd do {sitemap:{2}}, as the {2} is now after 
the colon, and thus an expression.

We could do with some documentation about this - as there's some 
interesting consequences that should be written about, and 
recommendations/bad practice. Any suggestions where?

Hope this is useful (and works)

Regards, Upayavira

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