Waf Task should use variant directory - waf

Question

I am creating files in a Task, the example code looks as follows:
from waflib import Task, TaskGen
def build(bld):
bld(features='write_file')
class xyz(Task.Task):
def run(self):
self.generator.path.get_bld().make_node(self.outputs[0].relpath())
#TaskGen.feature('write_file')
def make_tasks(self):
for x in range(20):
src = bld.path.find_node('wscript')
tgt = src.change_ext('.'+str(x))
tsk = self.create_task('xyz', src=src, tgt=tgt)
Now all files get placed inside the build directory, but I want them to be placed in build\abc. How do I do that? For normal builds, I can use a BuildContext and specify a variant:
from waflib.Build import BuildContext
class abc(BuildContext):
variant = 'abc'
But I can't get the BuildContext working on that example, and setting variant on a Task.Task does not work.
Update
I update the example based on neuros answer:
A minimal working example with this code looks like this:
from waflib import Task, TaskGen, Configure
Configure.autoconfig = True
def configure(cnf):
cnf.path.get_src().make_node('a/wscript').write('')
def build(bld):
bld(features='write_file')
class xyz(Task.Task):
def run(self):
self.generator.path.get_bld().find_or_declare(self.outputs[0].abspath()).write('')
#TaskGen.feature('write_file')
def make_tasks(self):
srcs = bld.path.ant_glob('**/wscript', excl='build')
for src in srcs:
build_dir_of_src = src.get_bld().parent
my_sub_node = build_dir_of_src.make_node('xyz')
my_sub_node.mkdir()
tgt_basename = src.name
tgt = my_sub_node.make_node(tgt_basename)
tsk = self.create_task('xyz', src=src, tgt=tgt)
The problem is that this creates the following:
build\xyz\wscript
build\a\xyz\wscript
But I want this:
build\xyz\wscript
build\xyz\a\wscript
So I just to create the folder xyz between build and what ever the tgt is. So exactly the behavior of variant in a BuildContext.

Answer 1

When tasks execute, you are already in a variant build dir. To control the outputs of a task you have to use the waflib.Node class API. In your example, change_ext get the source build directory equivalent and change the extension. To insert a subdir:
# [...]
build_dir_of_src = src.get_bld().parent
my_sub_node = build_dir_of_src.make_node("my_sub_dir")
my_sub_node.mkdir()
tgt_basename = src.change_ext('.' + str(x)).name
tgt = my_sub_node.make_node(tgt_basename)
# [...]
If you want to insert a "variant style" directory, you can use bld.bldnode (untested but you see the point, use bld.bldnode):
def get_my_bld(bld, src_node):
variant_like_dirname = "xyz"
my_bld_node = bld.bldnode.make_node(variant_like_dirname)
my_bld_node.mkdir()
rp = src_node.get_bld().relpath(bld.bldnode)
my_bld_target = my_bld_node.make_node(rp)
return my_bld_tgt
# [...]
tgt = get_my_bld(bld, src)
# [...]