Re: [Nant-users] Re: Segfault during compilation with mono on Linux

[Ian MacLean]

Gert Driesen wrote:
This is a legacy of Ant not having expressions or an if 
     

statement, so 
   

the only way to conditionally perform tasks was via this depends/if 
mechanism:

<target name="foo" depends="foo-test" if="${foo-exists}">
 <do-foo />
</target>
<target name="foo-test">
 <available file="foo.txt" property="foo-exists" />
</target>
     

Since NAnt now does have expressions then that behaviour 
doesn't make as 
much sense. You can achieve the same thing by putting the if 
test inside 
the target. However with the current behaviour you *can't* 
prevent both 
a target and its dependencies from being executed just by 
using the "if" 
attribute. This seems like one case where diverging from Ants 
behaviour 
might not be a bad thing. Certainly the current behaviour 
violates the 
"principle of least suprise".
   

I understand, but it does make sense that dependencies can have influence on
whether or not the target should be executed.
 

they can anyway :
<target name="foo" depends="foo-test" >
        <if test="${foo-exists}" >
                <do-foo />
        </if>
</target>
however right now you *can't* stop a target  *and* all its dependencies 
from being run  by using the  if attribute - and that seems like a big  
functionality hole.

I think the "stop this target and all its dependencies from running" 
use-case is a more common one than the:

"stop only this target but let all its dependencies execute" one.
Compatibility with Ant has never been a goal by itself, but we need very
strong arguments if we intend to break compatibility with Ant (in one of the
few where we ARE compattible ;-)) 

well - adding useful functionality seems like a pretty good reason - 
especially when the Ant behaviour is only there because they lack an 
expression system.

AND break backward compatibility for NAnt
users.
 

Sure - of course breaking compatibility is a bad thing generally - 
however in this case I think there are probably more users who are 
frustrated/confused by the current behaviour than are actively relying 
on it. I could be wrong though - I'd love to get peoples opinions on this.

If we keep the current behaviour (which I'd prefer), then we should at least
document it better, t make it more clear/obvious to users.
 

sure but documenting should be secondary to having it do the right thing.
Ian

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