Bill - Uh, you're right, and I am embarrassed to say that I am the author of the <stcheckout> task and I did not even remember my own code. I didn't think you were and looked at the code to disprove your suggestion but found you were correct.
So I could get the behavior I want by defining in the buildxml blank properties for every label I may want to define, and then via -D or a properties file I could optionally define those properties with a real label. That would work and it would not be too ugly. It will be my interim solution. However, I still agree with you that something like the Quiet Notation you describe would be an even better way to handle this. To reiterate the point, Costin listed five different ways of handling the case of an undefined property in a task attribute: 1) throw exception 2) replace it with "" 3) leave it unchanged ( current solution ) 4) don't set the property at all ( similar with what this proposal) 5) insert 'null' - the original implementation ( in whatever version we had in 99 :-) The point is that none of these will be correct in all use cases, but since a default must be chosen (#3 in this case), then there should be syntactical ways for the build-script writer to indicate each of the other four behaviors as the way to handle a missing property, on a per-use basis. I would like a solution like this because it gives the most freedom to the build-script writer while making it explicit from the script itself what is going on. I am less enamoured of solutions implemented in the java code or plug-ins because they are further from the build script writer. Yes, we developers can look at the source code, but Ant has a wider audience than java programmers. Even though I can look at and even change the java code of a task, when I am diddling with a script, that isn't something I want to do. If I as the author of a task can't remember how it works, what chance does the mere user have? I'd much rather be able to implement what I want via the script. Steve -----Original Message----- From: Bill Burton [mailto:[EMAIL PROTECTED] Sent: Fri 3/8/2002 11:08 PM To: Ant Developers List Cc: Subject: Re: [PROPOSE] task parameters that are only supplied when a property is defined Hello Steve, Here's a solution for <stcheckout> currently in CVS. Try calling <stcheckout> with a blank label, i.e. label="". You should find it ignores a blank label. Assuming that works, all you have to do is specify the lbl property as blank: <property name="lbl" value="" /> Then, if you want to use a label, either specify it to Ant as -Dlbl=labelName or use <properties file> to load a file of properties where lbl is defined to some value. This would have to be specified before the default blank value is set. You can use this technique for any attribute that ignores a blank value. The Quiet Notation syntax would work in this case as well. But the above solution is nearly as easy to use and works today. -Bill Steve Cohen wrote: > > I previously sent this idea in a message whose title may have hidden its > importance, but this is an idea I'd really like to see and I'd like the > developers to comment on it. > > What if there were a convenient syntax within ant for specifying task > attributes based on properties > > such that > > if the property were not set > the task code would never see the attribute? > > In other words, for example, look at this call: > <stcheckout URL="STARTEAM:49201/Aproject/AView" > username="auser" > password="secret" > rootlocalfolder="C:\dev\buildtest\co" > forced="true" > label = "${lbl}" > /> > > If the lbl property is defined, the task will get its value as the label > attribute. But if the lbl property is not defined, the task will get the > text "${lbl}" and most likely fail. > > I am proposing a new syntax that would allow a property to be specified with > a different meaning. Let's say this syntax is two dollar signs instead of > one ($${property}). (This may not be the optimal symbol for the ant parser, > but that is a detail - I am not wedded to any symbol). > > Using this syntax, the above example becomes: > > <stcheckout URL="STARTEAM:49201/Aproject/AView" > username="auser" > password="secret" > rootlocalfolder="C:\dev\buildtest\co" > forced="true" > label = "$${lbl}" > /> > > My proposal is that this syntax be interpreted this way: > > If the property lbl is defined, treat $${lbl} exactly as ${lbl} but > if the property lbl is not defined, do not even pass the label attribute to > the task. > > It seems to me that this would allow for much more flexible scripts, > especially when more than one parameter of a task is optional and there are > different use cases for the task. In the above example, to get the variable > functionality desired, I must include two blocks in my script, one with the > label attribute defined and the other without it, and put it some > conditionals to direct the processing to the right place. This can get > clumsy, especially if there are several attributes to parameterize; the > combinatorial possiblilities could be large, making for scripts that are > harder to understand or maintain. > -- To unsubscribe, e-mail: <mailto:[EMAIL PROTECTED]> For additional commands, e-mail: <mailto:[EMAIL PROTECTED]>
