Why can't waf find a path that exists? - waf

Question

Let's say I have x.y file in /mydir/a/b (on Linux)
When I run waf, it does not find the file.
def configure(context):
pass
def build(build_context):
build_context(source='/mydir/a/b/x.y',
rule='echo ${SRC} > ${TGT}',
target='test.out')
Result: source not found: '/mydir/a/b/x.y' in bld(features=[], idx=1, meths=['process_rule', 'process_source'] ...
Ok, maybe you want a relative path, Waf? And you are not telling me?
def build(context):
path_str = '/mydir/a/b'
xy_node = context.path.find_dir(path_str)
if xy_node is None:
exit ("Error: Failed to find path {}".format(path_str))
# just refer to the current script
orig_path = context.path.find_resource('wscript')
rel_path = xy_node.path_from(orig_path)
print "Relative path: ", rel_path
Result: Error: Failed to find path /mydir/a/b
But that directory exists! What's up with that?
And, by the way, the relative path for some subdirectory (which it can find) is one off. e.g. a/b under current directory results in relative path "../a/b". I'd expect "a/b"

Answer 1

In general there are (at least) two node objects in each context:
- path: is pointing to the location of the wscript
- root: is pointing to the filesystem root
So in you case the solution is to use context.root:
def build(context):
print context.path.abspath()
print context.root.abspath()
print context.root.find_dir('/mydir/a/b')

Answer 2

Hmm, looks like I found an answer on the waf-users group forum, answered by Mr. Nagy himself:
The source files must be present under the top-level directory. You
may either:
create a symlink to the source directory
copy the external source files into the build directory (which may cause problem if there is a structure of folders to copy)
set top to a common folder such as '/' (may require superuse permissions, so it is a bad idea in general)
The recommendation in conclusion is to add a symlink to the outside directory during the configuration step. I wonder how that would work, if I need this on both, Linux and Windows...

Answer 3

Just pass the Node to the copy rule instead of passing the string representing the path:
def build(build_context):
source_node = build_context.root.find_node('/mydir/a/b/x.y')
build_context(source=source_node,
rule='echo ${SRC} > ${TGT}',
target='test.out')
Waf will be able to find the file even if outside of the top level directory.