Add arguements to extends() and activate/deactivate.

lib/spack/spack/package.py

@@ -497,16 +497,26 @@ def fetcher(self, f):
     @property
     def extendee_spec(self):
         """Spec of the extendee of this package, or None if it is not an extension."""
-        if not self.extendees:     return None
-
+        if not self.extendees:
+            return None
         name = next(iter(self.extendees))
         if not name in self.spec:
-            return self.extendees[name]
+            spec, kwargs = self.extendees[name]
+            return spec
 
         # Need to do this to get the concrete version of the spec
         return self.spec[name]
 
 
+    @property
+    def extendee_args(self):
+        """Spec of the extendee of this package, or None if it is not an extension."""
+        if not self.extendees:
+            return None
+        name = next(iter(self.extendees))
+        return self.extendees[name][1]
+
+
     @property
     def is_extension(self):
         return len(self.extendees) > 0
@@ -949,6 +959,8 @@ def _check_extendable(self):
 
 
     def _sanity_check_extension(self):
+        if not self.is_extension:
+            raise ValueError("This package is not an extension.")
         extendee_package = self.extendee_spec.package
         extendee_package._check_extendable()
 
@@ -967,14 +979,14 @@ def do_activate(self):
         activate() directly.
         """
         self._sanity_check_extension()
-        self.extendee_spec.package.activate(self)
+        self.extendee_spec.package.activate(self, **self.extendee_args)
 
         spack.install_layout.add_extension(self.extendee_spec, self.spec)
         tty.msg("Activated extension %s for %s."
                 % (self.spec.short_spec, self.extendee_spec.short_spec))
 
 
-    def activate(self, extension):
+    def activate(self, extension, **kwargs):
         """Symlinks all files from the extension into extendee's install dir.
 
         Package authors can override this method to support other
@@ -983,17 +995,20 @@ def activate(self, extension):
         always executed.
 
         """
+        ignore_files = set(spack.install_layout.hidden_file_paths)
+        ignore_files.update(kwargs.get('ignore', ()))
+
         tree = LinkTree(extension.prefix)
-        conflict = tree.find_conflict(
-            self.prefix, ignore=spack.install_layout.hidden_file_paths)
+        conflict = tree.find_conflict(self.prefix, ignore=ignore_files)
         if conflict:
             raise ExtensionConflictError(conflict)
-        tree.merge(self.prefix, ignore=spack.install_layout.hidden_file_paths)
+        tree.merge(self.prefix, ignore=ignore_files)
 
 
     def do_deactivate(self):
+        """Called on the extension to invoke extendee's deactivate() method."""
         self._sanity_check_extension()
-        self.extendee_spec.package.deactivate(self)
+        self.extendee_spec.package.deactivate(self, **self.extendee_args)
 
         if self.spec in spack.install_layout.get_extensions(self.extendee_spec):
             spack.install_layout.remove_extension(self.extendee_spec, self.spec)
@@ -1002,7 +1017,7 @@ def do_deactivate(self):
                 % (self.spec.short_spec, self.extendee_spec.short_spec))
 
 
-    def deactivate(self, extension):
+    def deactivate(self, extension, **kwargs):
         """Unlinks all files from extension out of this package's install dir.
 
         Package authors can override this method to support other
@@ -1011,8 +1026,11 @@ def deactivate(self, extension):
         always executed.
 
         """
+        ignore_files = set(spack.install_layout.hidden_file_paths)
+        ignore_files.update(kwargs.get('ignore', ()))
+
         tree = LinkTree(extension.prefix)
-        tree.unmerge(self.prefix, ignore=spack.install_layout.hidden_file_paths)
+        tree.unmerge(self.prefix, ignore=ignore_files)
 
 
     def do_clean(self):

lib/spack/spack/relations.py

@@ -117,7 +117,7 @@ def depends_on(*specs):
             dependencies[spec.name] = spec
 
 
-def extends(*specs):
+def extends(spec, **kwargs):
     """Same as depends_on, but dependency is symlinked into parent prefix.
 
     This is for Python and other language modules where the module
@@ -126,6 +126,10 @@ def extends(*specs):
     but allowing ONE module version to be symlinked into a parent
     Python install at a time.
 
+    keyword arguments can be passed to extends() so that extension
+    packages can pass parameters to the extendee's extension
+    mechanism.
+
     """
     pkg = get_calling_package_name()
     clocals = caller_locals()
@@ -134,12 +138,11 @@ def extends(*specs):
     if extendees:
         raise RelationError("Packages can extend at most one other package.")
 
-    for string in specs:
-        for spec in spack.spec.parse(string):
+    spec = Spec(spec)
     if pkg == spec.name:
         raise CircularReferenceError('extends', pkg)
     dependencies[spec.name] = spec
-            extendees[spec.name] = spec
+    extendees[spec.name] = (spec, kwargs)
 
 
 def provides(*specs, **kwargs):

var/spack/packages/python/package.py

@@ -28,6 +28,16 @@ def install(self, spec, prefix):
         make("install")
 
 
+    @property
+    def python_lib_dir(self):
+        return os.path.join('lib', 'python%d.%d' % self.version[:2])
+
+
+    @property
+    def site_packages_dir(self):
+        return os.path.join(self.python_lib_dir, 'site-packages')
+
+
     def setup_extension_environment(self, module, spec, ext_spec):
         """Called before python modules' install() methods.
 
@@ -39,11 +49,29 @@ def setup_extension_environment(self, module, spec, ext_spec):
         module.python = Executable(join_path(spec.prefix.bin, 'python'))
 
         # Add variables for lib/pythonX.Y and lib/pythonX.Y/site-packages dirs.
-        module.python_lib_dir = join_path(ext_spec.prefix.lib, 'python%d.%d' % self.version[:2])
-        module.site_packages_dir = join_path(module.python_lib_dir, 'site-packages')
+        module.python_lib_dir = os.path.join(ext_spec.prefix, self.python_lib_dir)
+        module.site_packages_dir = os.path.join(ext_spec.prefix, self.site_packages_dir)
 
         # Add site packages directory to the PYTHONPATH
         os.environ['PYTHONPATH'] = module.site_packages_dir
 
         # Make the site packages directory if it does not exist already.
         mkdirp(module.site_packages_dir)
+
+
+    def add_ignore_files(self, args):
+        """Add some ignore files to activate/deactivate args."""
+        ignore  = set(args.get('ignore', ()))
+        ignore.add(os.path.join(self.site_packages_dir, 'site.py'))
+        ignore.add(os.path.join(self.site_packages_dir, 'site.pyc'))
+        args.update(ignore=ignore)
+
+
+    def activate(self, ext_pkg, **args):
+        self.add_ignore_files(args)
+        super(Python, self).activate(ext_pkg, **args)
+
+
+    def deactivate(self, ext_pkg, **args):
+        self.add_ignore_files(args)
+        super(Python, self).deactivate(ext_pkg, **args)