genrule() documentation has incorrect example

[spearce]

The example for genrule() shows:

cmd = 'python $SRC_0 $SRC_1 > $OUT',

which does not work. $SRC_0 seems to be not implemented in BUCK. I suspect you meant:

cmd = 'python $SRCDIR/basic_to_full_manifest.py $SRCDIR/AndroidManifest.xml'

[bolinfest]

Actually, I believe it should just be:

cmd = 'python basic_to_full_manifest.py AndroidManifest.xml'

is that not working for you?

[spearce]

Well, this was a reminder to fix the documentation. :-)

And it doesn't work if the name is a genfile().

[bolinfest]

Ah, yes, now I am feeling your pain. I just made it possible to build the Closure Compiler using Buck, and I had to do some hacky things, as well (see /closure/closure-compiler/BUCK):

http://code.google.com/p/plovr/source/detail?r=50a647db8b87f361efcf382491790f0a582ce49f

[spearce]

What about having a macro inside of the cmd string like "$(location //x:y)" to give you the location of a srcs entry named "//x:y". If //x:y is e.g. a java_library() this is the JAR it produces, if its a java_application() again its only the JAR it makes and not the execution command line, if its a genrule() its the out file. Such references in srcs should also automatically be added to the dep list so its not necessary to repeat them in deps.

Buck already seems to do this with ${//x:y} for the name of the tool to execute, but that expansion isn't suitable because it creates things like "java -classpath ..." or "PYTHONPATH= ..." which isn't suitable in all contexts. $(location //x:y) would expand only to the path of the source file.

[bolinfest]

I believe this is fixed now: http://facebook.github.io/buck/rule/genrule.html

Though the section on deps mentions the old curly-brace pattern, but I'll send out a fix for that now.