setup_extension_environment is now setup_dependent_environment.

- other packages, like Qt, can now use this to set up relevant build
  variables and env vars for their dependencies.

- not just extensions anymore.

lib/spack/spack/package.py

@@ -829,10 +829,10 @@ def do_install(self, **kwargs):
                 self.stage.chdir_to_source()
                 build_env.setup_package(self)
 
-                # Allow extendees to further set up the environment.
-                if self.is_extension:
-                    self.extendee_spec.package.setup_extension_environment(
-                        self.module, self.extendee_spec, self.spec)
+                # Allow dependencies to further set up the environment.
+                for dep_spec in self.spec.traverse(root=False):
+                    dep_spec.package.setup_dependent_environment(
+                        self.module, dep_spec, self.spec)
 
                 if fake_install:
                     self.do_fake_install()
@@ -910,8 +910,8 @@ def module(self):
                           fromlist=[self.__class__.__name__])
 
 
-    def setup_extension_environment(self, module, spec, ext_spec):
-        """Called before the install() method of extensions.
+    def setup_dependent_environment(self, module, spec, dependent_spec):
+        """Called before the install() method of dependents.
 
         Default implementation does nothing, but this can be
         overridden by an extendable package to set up the install
@@ -930,6 +930,8 @@ def setup_extension_environment(self, module, spec, ext_spec):
            put a 'python' Execuable object in the module scope for the
            extension package to simplify extension installs.
 
+        3. A lot of Qt extensions need QTDIR set.  This can be used to do that.
+
         """
         pass
 

var/spack/packages/python/package.py

@@ -46,7 +46,7 @@ def site_packages_dir(self):
         return os.path.join(self.python_lib_dir, 'site-packages')
 
 
-    def setup_extension_environment(self, module, spec, ext_spec):
+    def setup_dependent_environment(self, module, spec, ext_spec):
         """Called before python modules' install() methods.
 
         In most cases, extensions will only need to have one line::

var/spack/packages/qt/package.py

@@ -1,3 +1,4 @@
+import os
 from spack import *
 
 class Qt(Package):
@@ -20,6 +21,11 @@ class Qt(Package):
     depends_on("libmng")
     depends_on("jpeg")
 
+    def setup_dependent_environment(self, module, spec, dep_spec):
+        """Dependencies of Qt find it using the QTDIR environment variable."""
+        os.environ['QTDIR'] = self.prefix
+
+
     def patch(self):
         # Fix qmake compilers in the default mkspec
         qmake_conf = 'mkspecs/common/g++-base.conf'