Merge pull request #299 from epfl-scitas/enhancement/os_detection

enhancement proposal : boolean support for when=<arg>

lib/spack/spack/directives.py

@@ -174,7 +174,11 @@ def version(pkg, ver, checksum=None, **kwargs):
 
 
 def _depends_on(pkg, spec, when=None):
-    if when is None:
+    # If when is False do nothing
+    if when is False:
+        return
+    # If when is None or True make sure the condition is always satisfied
+    if when is None or when is True:
         when = pkg.name
     when_spec = parse_anonymous_spec(when, pkg.name)
 

lib/spack/spack/multimethod.py

@@ -193,10 +193,11 @@ def install(self, prefix):
        platform-specific versions.  There's not much we can do to get
        around this because of the way decorators work.
     """
-class when(object):
     def __init__(self, spec):
         pkg = get_calling_module_name()
-        self.spec = parse_anonymous_spec(spec, pkg)
+        if spec is True:
+            spec = pkg
+        self.spec = parse_anonymous_spec(spec, pkg) if spec is not False else None
 
     def __call__(self, method):
         # Get the first definition of the method in the calling scope
@@ -207,7 +208,9 @@ def __call__(self, method):
         if not type(original_method) == SpecMultiMethod:
             original_method = SpecMultiMethod(original_method)
 
-        original_method.register(self.spec, method)
+        if self.spec is not None:
+            original_method.register(self.spec, method)
+
         return original_method