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From Dominique Devienne <DDevie...@lgc.com>
Subject RE: Request: Change <javac> debug default to "on"
Date Thu, 07 Nov 2002 15:58:53 GMT
I think I agree with what you are saying, just not on the solution proposed.


I don't like the magic properties either. But as I've said before, this kind
of things could be handle more generically, and more expressively (IMHO,
which Costin seemed to disagree with last time I exposed this) using a
generic mechanism to assign attribute values in Ant which is similar to the
Xdefault way of assigning resources, but uses an XPath syntax.

Just consider the XPath view of all your build files, and simply select all
the attributes you want to assign with the right XPath query. E.g.

//javac/@debug = true

This could also replace (supercede) the build.compiler property to say for
example

//javac/compiler = jikes

As I said before, not having such a mechanism forces to use too many
properties with defaults, just so it's override able. Having this generic
way to override things would be very powerful (and based on an XML standard
like XPath too!).

It would also allow changing the defaults of any task attribute that is not
appropriate for the site, and build file writers.

I don't really know the right place to issue such overrides, but maybe it
should be another XML files constituting the *environment* of Ant, like
global attribute definition override (like described above), logger and/or
listeners to use, taskdefs/typedefs common to many build files, etc...

Such a global config file to Ant could also define additional site-specific
default exclude patterns (instead of having to hard-code them in Ant), and
generally tune the global policies used internally by Ant...

It seems to me sometimes I'm the only one who thinks such thoughts, and that
doesn't end to surprise me ;-) I guess I must be special... Please no
comments on how special ;-) --DD

-----Original Message-----
From: Jose Alberto Fernandez [mailto:jalberto@cellectivity.com] 
Sent: Thursday, November 07, 2002 8:05 AM
To: Ant Developers List
Subject: RE: Request: Change <javac> debug default to "on"


> From: Gus Heck [mailto:gus-antdev@cognition.olin.edu]
> 
> Did he say magic property? uh oh...
> 
> (Mail shield up)
> 
> Magic properties have been fairly unpopular. They generally obfuscate 
> behavior, and clutter up the namespace available for 
> properties. In this 
> case it would put critical information (critical for some at least) 
> about what javac is really doing in an obscure location away from the 
> invocation of the javac task.
> 

Do you think that build files would be easier to write or more flexible if
we had to specify which compiler to use on each individual <javac> task?
I would think that it is very rare the case in which you want some files
compiled by
one compiler and other files with a different compiler. Moreover, different
people on the same project may want to use different compilers.

"Magic properties" in reality are no other thing than global-predefined user
preferences;
and it makes a lot of sense for this kind of usage.

> Besides this I am not sure why setting a property would be 
> better than 
> setting the flag in javac. The point under discussion is should the 
> _default_behavior_ change. There isn't really any need for a 
> new way to 
> customize the behavior of javac globally is there?
> 

Well a very important point of the discussion is the alleged cost of
changing
all those build files if we change this default behavior. The only thing I
am proposing
is a way to define this default behaviour as a preference of the user (or
developement environment).
Just the same as the compiler preference does.

Jose Alberto

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