[Distutils] Buildout 2 and system packages

[Ralf Schmitt]

Lele Gaifax <lele at metapensiero.it> writes:

> Jim Fulton <jim at zope.com> writes:
>
>> The problem is that site-packages doesn't have a predictable
>> location, as demonstrated by the example given in this thread.  On
>> some systems, there are multiple directories containing custom
>> modules.
>
> Sorry to insist (being dumb :), but couldn't buildout, that should know
> the list of explicitly requested distributions, sort the paths giving
> precedence to them?

The following uses working_set.resolve to do that. I may miss some
details here, but it looks like this can be done in a sane way...

diff --git a/src/zc/buildout/easy_install.py b/src/zc/buildout/easy_install.py
index 75f7047..48acda0 100644
--- a/src/zc/buildout/easy_install.py
+++ b/src/zc/buildout/easy_install.py
@@ -889,7 +889,14 @@ def scripts(reqs, working_set, executable, dest=None,
             ):
     assert executable == sys.executable, (executable, sys.executable)
 
-    path = [dist.location for dist in working_set]
+    if isinstance(reqs, str):
+        raise TypeError('Expected iterable of requirements or entry points,'
+                        ' got string.')
+
+    parsed_requirements = [pkg_resources.Requirement.parse(req) for req in reqs if isinstance(req, str)]
+    path = [dist.location for dist in working_set.resolve(parsed_requirements)]
+    path.extend([dist.location for dist in working_set])
+
     path.extend(extra_paths)
     # order preserving unique
     unique_path = []
@@ -900,9 +907,6 @@ def scripts(reqs, working_set, executable, dest=None,
 
     generated = []
 
-    if isinstance(reqs, str):
-        raise TypeError('Expected iterable of requirements or entry points,'
-                        ' got string.')
 
     if initialization:
         initialization = '\n'+initialization+'\n'