DSL Support for Brail
time to read 4 min | 732 words

First things first, Harris Boyce III has done all the work, my sum contribution to this feature has included some wild cheering from the side lines.

That said, this is one cool feature. Let us explore it.

There are a lot of people who consider anything resembling <html> tags to be a mess, associate them with ASP Classic mistakes, and reject them out of hand. I think that this is a mistake, but I gave up changing the whole world overnight, now I have busy formulating three steps plans that takes a week...

At any rate, consider this output:

<html>
	<body>
		<table>
			<tr>
				<th>Names</th>
			</tr>
			<tr>
				<td>Ayende</td>
			</tr>
			<tr>
				<td>Rahien</td>
			</tr>
		</table>
	</body>
</html>

How would we generate this output using Brail? The classic approach is:

<html>
	<body>
		<?brail
                       component Grid, {"source": names}:
                         	section header:
                                    output "<tr><th>Names</th><tr>"
                               	end
                             	section item:
                        	    output "<tr><td>${item}</td><tr>"
                           	end
                        end
		?>		
	</body>
</html>

This works, but it not really Jump-Up-And-Down-All-Excited code. And, of course, some people faint dead away from having to deal with raw HTML, "Give me my components or give me death!"

Now, here is the DSL way of doing it:

<?brail
dsl Html:
	body:
		component GridComponent, {"source" : names}:
			section header:
				tr:
					th:
						text "Names"
					end
				end
			end 
			
			section item:
				td:
					text item
				end
			end
		end
	end
end
?>

And this baby produces the same output as the previous one.

Now, you are probably aware that I am not really fond of raising the abstraction level needlessly, so why is this a good thing? Well, because it means that you can now do stuff like this:

dsl.Register(atom)
dsl:
   feed:
       title:
           div:
               text "some content"
           end
       end
   end
end

And it will be able to produce semantically correct ATOM feed. (To be exact, it would be if we had an AtomExtension implementation to the new IDslLanguageExtension interface, which we currently don't have).

There are some quirks in the implementation, but it is a very cool direction to go to.

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