OK, here's my idea NAnt world:
Scopable properties
Parameter variables
Return values
In other words, I want it to work more like a functional language. The
closest model I can think of is XSLT. It seems to me that these elements
could greatly simplify the coding of complex build script logic without
introducing many changes or extensions to the NAnt language. In fact, I
would argue, that the fact that NAnt doesn't have any of these 3 ideas
actually makes it harder for newcomers to learn (at least it did for
me).
Scoping could be done implicitly as it generally is in scripting
languages. The scope of a variable (property) is the container in which
it is declared. So a property declared inside a template element is only
visible within that template; a property declared outside a template is
global to that build.
Parameter variables could be done something like xslt:
<call target="myTarget">
<with-param name="myParam" value="Foo" />
</call>
Returns could also follow an xslt-like pattern:
<property name="myResult">
<call target="myTarget">
<with-param name="myParam" value="Foo" />
</call>
</property>
And here's the target (it's a little different from XSLT in that build
files aren't made to produce text output, so it makes sense to
explicitly return something (XSLT just returns whatever the template
spits into standard out)):
<target name="myTarget">
<param name="myParam" />
<return>true</return>
</target>
It seems to me all 3 extensions could be introduced without introducing
breaking changes. Except for implicitly scoping property declarations.
Might want to think carefully about that one.
________________________________
Gary McCullough
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Troy Laurin
Sent: Tuesday, August 10, 2004 11:10 PM
To: Nant-Users (E-mail)
Subject: Property change-suggestions, was RE: [Nant-users] can't
overwrite property
I'm sure people are sick of getting a slough of mails from me, so I'll
combine these ones :-)
Richard Poole wrote:
> I'm relatively new to NAnt so please forgive me if this is a
rubbish/old idea. :)
>
> --- C# snippet ---
>
> public void MyFunction()
> {
> int a = 2; // const or not...
> {
> int a = 4; // ...a will now be equal to 4...
> }
> // ...but now a equals 2 again.
> }
>
> --- NAnt build script snippet ---
>
> <property name="a" value="2" /> <!-- readonly or not... -->
> <someelement>
> <property name="a" value="4" /> <!-- ...a will now be equal to
4... -->
> </someelement>
> <!-- ...but now a equals 2 again. -->
What about the following C# scenario:
public void MyFunction() {
int a = 2; // const or not...
{
a = 4; // note non-redefinition of a
}
// ...a now equals 4!!
}
How could this be expressed in a NAnt script?
It might be possible to introduce a 'scope' attribute to the property
task, but there are quite a few other tasks which set property values...
being able to determine the scope for these variables would mean a
potential blowout in extra attributes, making NAnt harder to learn for
newcomers.
Global-scope properties (or variables) need to be available... a simple
example requiring this is an 'init' target, which creates a log file or
folder corresponding to the current time, and then sets the path to this
file/folder in a property, so other targets can write their logs to the
correct location.
McCullough, Gary wrote:
> I like this idea. But even better I like the idea of making
> explicit parameters. Something I've mentioned before.
> Parameters and locals would go a long way toward simplifying
> build file logic, I think.
>
> For instance, adapting XSLT conventions, suppose you had a
> construction like this in your build file:
>
> <param name="outputDir" default=".\output\" />
>
> And you fired your build file, overriding the default
> outputDir value, something like this:
>
> Nant.exe myprogram.build -D:outputDir="c:\builds\myprogram\bin\"
>
> However, we still have to figure out how to handle the
> breaking change it would introduce.
I find this idea intriguing, but I'm concerned that the complexity is
subtle and potentially fatal.
The biggest issue that I can see is how to differentiate between
properties and parameters? If they use the same expression syntax ${}
to access their values, then how do you deal with name conflicts?
Gert Driesen wrote:
> The easiest, and in my opinion best, solution is to mark the
> properties that you want to be able to override on the
> command line with overwrite="false".
>
> That way the property task will not attempt to overwrite the
> value of the property (that was, for example, specified on
> the command line).
I think that this, plus changing commandline parameters to not be
read-only would remove much of the confusion for people new-come to
NAnt. There would of course be a ramp-across cost for Ant users, but
there have already been enough changes between Ant and NAnt to suggest
the need for a migration guide. The addition of a function to determine
the command-line value of a parameter should cover all cases?
Comments?
-T
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