[Ant-user] Syntax for Names: target, property, macrodef, etc.

Anything goes really, AFAIK. There is no specifications.

Some names will create issues, for example <target name="-foo"> can't
be called from the command line because -foo will be interpreted as a
CLI switch and since not found Ant will error out. This "behavior" is
relied upon to have "private" targets.

Also remember this is XML land, so attribute whitespace normalization
will apply (depending on the parser used possibly) which may result in
some whitespaces being removed.

But aside from these quirks, Ant does not put any restrictions on
names in general. --DD

PS: Also keep in mind that property expansion does occurs inside these
names, but I assume you mean the names after expansion.

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Hi Dominique,

Thanks for the info. And, also thanks for the specific example of the leading "-" character.

Because Ant has only a global namespace for property names (and other names like macrodef, etc.), and for the case that a particular
ant script inherits properties from the caller, I'm adopting a convention that will help us know whether a particular name is local
to the being-called ant script. In particular, I'm favoring the convention that "local" names begin with a dot. We guarantee that
the caller never has defined any names that begin with a dot, so there is never a problem with conflicts. I had considered both the
"-" and the "." as a leading character to indicate the name is local. But, you've given a good reason to avoid "-". Thanks!

Enjoy,
Steve Amerige
SAS Institute, Deployment Software Developer


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Hmmm, I believe that's wrong on second thought.

Target names are not expanded I now recall, and it's probably the same
for property and macro names.

Someone might want to give a more definitive answer on that. --DD

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A property name would be expanded as in <property name="value.${foo}"
value="bar" />. I never thought about macrodefs, and I don't think we
have any generic way to call a macro defined in such a fashion (though
ISTR having played with such at some point long ago), but I think it
*would* be expanded.

Matt
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Hi Dominique and all,

After considering that scriptdef, macrodef, and perhaps some other tags do not allow neither the "-" nor the "." as an initial
character, I'm going to use the "_" character name prefix to indicate that a name is "local" to the current JVM. For example:

<var name="_i" value="1"/>

Again, the point of this convention is to workaround the fact that my understanding is that there is no scoping for *property*,
*var*, and other names in Ant. So, is my understanding incorrect?

Can one use namespaces to have real local variables, properties, etc.? Is there any notion of scoping? I'd love to hear what Ant
is capable of doing with respect to var, property, macrodef, scriptdef, etc. scoping for Ant 1.6, 1.7, and 1.8.

Thanks for your help.... it's very much appreciated!

Best regards,
Steve Amerige
SAS Institute, Deployment Software Developer

Certainly there isn't much in the way of scoping for earlier versions
of Ant, though you can do things with varying degrees of success using
libraries along the lines of ant-contrib (there are most likely others
to assist in this). As of Ant 1.8, the <local> task was provided to
declare a "level of locality" for a named property, i.e. "any changes
made to property P at or below the current scope are considered local
to this block." The manual page for this task describes its use in
what I consider adequate (at least) detail. As it took some doing (by
Peter O'Reilly as well as myself, if I recall correctly) to get this
functioning properly, I would heartily recommend its use.

Matt
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When I look at the 1.8.2 codebase, I see in:

ant-1.8.2\src\main\org\apache\tools\ant\taskdefs\MacroDef.java

/**
* Check if a character is a valid character for an element or
* attribute name.
*
* @param c the character to check
* @return true if the character is a letter or digit or '.' or '-'
* attribute name
*/
public static boolean isValidNameCharacter(char c) {
// ? is there an xml api for this ?
return Character.isLetterOrDigit(c) || c == '.' || c == '-';
}

This seems to be at odds with the specification:

http://www.w3.org/TR/xml/#sec-common-syn


Names and Tokens

[4] |NameStartChar| ::= |":" | [A-Z] | "_" | [a-z] | [#xC0-#xD6] | [#xD8-#xF6] | [#xF8-#x2FF] | [#x370-#x37D] | [#x37F-#x1FFF]
[4a] |NameChar| ::= |NameStartChar <http://www.w3.org/TR/xml/#NT-NameStartChar> | "-" | "." | [0-9] | #xB7 | [#x0300-#x036F] |
[#x203F-#x2040]|
[5] |Name| ::= |NameStartChar <http://www.w3.org/TR/xml/#NT-NameStartChar> (NameChar <http://www.w3.org/TR/xml/#NT-NameChar>)*|
[6] |Names| ::= |Name <http://www.w3.org/TR/xml/#NT-Name> (#x20 Name <http://www.w3.org/TR/xml/#NT-Name>)*|
[7] |Nmtoken| ::= |(NameChar <http://www.w3.org/TR/xml/#NT-NameChar>)+|
[8] |Nmtokens| ::= |Nmtoken <http://www.w3.org/TR/xml/#NT-Nmtoken> (#x20 Nmtoken <http://www.w3.org/TR/xml/#NT-Nmtoken>)*|


I've also looked at:

ant-1.8.2\src\main\org\apache\tools\ant\taskdefs\AntStructure.java

/**
* Does this String match the XML-NMTOKEN production?
* @param s the string to test
* @return true if the string matches the XML-NMTOKEN
*/
public static final boolean isNmtoken(String s) {
final int length = s.length();
for (int i = 0; i < length; i++) {
char c = s.charAt(i);
// XXX - we are committing CombiningChar and Extender here
if (!Character.isLetterOrDigit(c)
&& c != '.' && c != '-' && c != '_' && c != ':') {
return false;
}
}
return true;
}

Maybe I'm looking at the wrong part in the code for where *element* names (such as macrodef and scriptdef) are validated and where
other names (such as property name="...") are validated. But, the Ant code doesn't match what is specified by the XML BNF. Also,
the XML BNF doesn't seem to allow spaces in a *Name* object. Is there an Ant BNF specification that reflects the code?

Is there any formal specification for Ant syntax? Where do I find it?

Sorry to be a bother! But, I'm just trying to be very clear in understanding Ant and am hoping that a formal specification exists.

Many thanks!
Steve Amerige
SAS Institute, Deployment Software Developer

This method is indeed used to validate attribute names and names of
nested elements of tasks defined as macrodefs (but not for the taks name
itself which is not formally restricted at all).
Quite possible, we never really targeted full conformance but somethign
I'd call "good enough".
AntStructure is a task that has been writen ages ago to write an
approximation of a DTD for a running Ant instance (each Ant run could in
fact produce a different DTD because new elements would be added by
taskdefs). The task has never claimed to be useful 8-)
You are.

In the end the XML parser decides what is a valid name and what is not.
Ant will not stop you from creating tasks with macro/script/taskdef that
are nor legal XML element names, you will just not be able to use them
because the parser will bail out. We do have some checks in place but
they are - as you've found out - incomplete or even wrong.

For "normal" tasks - tasks written in Java - attribute names and names
of nested elements are determined by method names and thus are way more
restricted than their XML counterparts. You can't have a "." or a "-"
in a method name and thus can't write a task in Java with an attribute
that would contain such a character.

I don't think we have any rules on property names at all. Same for
target names. Beyond the restrictions the XML parser will create, that
is (obviously you can't contains a 0 character in any XML document).

Some names will put you into trouble, though. Target names that
contains commas (quite possible we prohibit it, not sure) would be
unusable in a depends attribute of a different target for example.
Properties whose names contain "$" or "}" will be difficult to use as
well.
This is true. If you feel there is a real problem, feel free to provide
a patch 8-). The difference between the formal specification and Ant's
code is likely to be in areas that haven't caused problems in practice
(or bugs would have been reported).
I'm afraid there isn't. The various IDE integration projects that
support writing Ant build files may have something, but even than you
can't be sure it will contain the full truth or rather "just work in
practice".

Sorry

Stefan

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