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From Stefan Bodewig <bode...@bost.de>
Subject Re: [RFE] Richer Task Specification
Date Tue, 20 Jun 2000 08:35:28 GMT
>>>>> "mf" == mpfoemme  <mpfoemme@ThoughtWorks.com> writes:

 mf> What if we allow all tasks (as opposed to just properties and
 mf> taskdefs) to be used outside of targets , and execute them on the
 mf> spot?

I agree with Sam that this would remove the special case we have for
properties and taskdefs but actually would prefer it the other way
around.

My proposal:

1. Don't treat properties as tasks at all. Don't even say they are
tasks in the documentation.

2. Do the same for taskdefs.

3. Don't instantiate tasks before they get executed.

4. Merge init and execute into a single method that gets called right
after the task has been configured.

This should enable the late compilation of tasks and remove some of
the darker sides of Ant (the "weird behavior of available" for
example) at the same time.

The only tricky thing in this is part 3. 

One solution would be to revert to a DOM tree and defer parsing of the
tree part below targets until the target gets executed. Neither too
difficult nor elegant.

Another solution would be the proxy pattern Sam suggested a while
back. Configure a proxy object for the task at parse time and that
again instantiates, configures and executes the task when it's time to
get the work done.

This latter solution might even have the additional power to choose
between several special implementations of a generic task (choose
between classic/modern javac or jikes or ..., choose the vendor
implementation of idl2java, sqlj or similar things) like Valentin
suggested. I'm not sure how to implement this easily without having to
modify all existing tasks though.

The only drawback I can see is that errors like misspelled attribute
names in the build.xml won't get caught before the task gets executed
as the proxies would need to accept all attributes.

Comments?

Stefan


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