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From Steve Loughran <ste...@apache.org>
Subject Re: Question about "depends" attribute in the target element
Date Wed, 14 Nov 2007 17:28:12 GMT
David Weintraub wrote:
> If you invoke multiple targets on the command line, each target will
> execute, and dependencies will execute independently. There is no way
> of Ant to know if one of the targets you put on the command line might
> affect a later target. For example:
> 
> $ ant first clean_first second
> 
> If Ant kept track of targets already executed, it would be messed up
> by the "clean_first" target. Target "second" depends upon "first", but
> "clean_first" destroyed what files "first" had built. That's why each
> target will execute all of its dependencies.
> 
> However, this works fine:
> 
> <project name="test">
> <target name="first"/>
> <target name="second" depends="first"/>
> <target name="third" depends="first,second"/>
> </project>
> 
> Executing:
> 
> $ ant third
> [first]
> [second]
> [third]
> 
> Executes target "first" only a single time

There is actually a way to maybe get Ant to resolve dependencies across 
targets on the command line, but it isnt exposed to the end user. Inside 
ant there are these things called Executors that decide which targets to 
run next. The normal executor runs everything on the command line. If 
you go -keepgoing, a new executor runs targets that dont depend on 
targets that have failed; it 'keeps going' as well as it can. You could 
probably add a new executor that took intra-target dependencies into 
account, and switch to it using whichever magic property identifies the 
new executor. This is pretty low level though; I don't know anyone who 
has done this.

-- 
Steve Loughran                  http://www.1060.org/blogxter/publish/5
Author: Ant in Action           http://antbook.org/

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