Fix pex-tool#309 by deduplicating output of the distribution finder. (p…

…ex-tool#310)

pex/environment.py

@@ -82,17 +82,20 @@ def write_zipped_internal_cache(cls, pex, pex_info):
           distribution_name, dist_digest))
         if os.path.exists(cached_location):
           dist = DistributionHelper.distribution_from_path(cached_location)
-          existing_cached_distributions.append(dist)
-          continue
+          if dist is not None:
+            existing_cached_distributions.append(dist)
+            continue
         else:
           dist = DistributionHelper.distribution_from_path(os.path.join(pex, internal_dist_path))
-          if DistributionHelper.zipsafe(dist) and not pex_info.always_write_cache:
-            zip_safe_distributions.append(dist)
-            continue
+          if dist is not None:
+            if DistributionHelper.zipsafe(dist) and not pex_info.always_write_cache:
+              zip_safe_distributions.append(dist)
+              continue
 
         with TRACER.timed('Caching %s' % dist):
           newly_cached_distributions.append(
             CacheHelper.cache_distribution(zf, internal_dist_path, cached_location))
+
     return existing_cached_distributions, newly_cached_distributions, zip_safe_distributions
 
   @classmethod

pex/util.py

@@ -89,9 +89,9 @@ def distribution_from_path(cls, path, name=None):
     # Monkeypatch pkg_resources finders should it not already be so.
     register_finders()
     if name is None:
-      distributions = list(find_distributions(path))
+      distributions = set(find_distributions(path))
       if len(distributions) == 1:
-        return distributions[0]
+        return distributions.pop()
     else:
       for dist in find_distributions(path):
         if dist.project_name == name: