Fix corner case in cached dependency resolution

pex/resolver.py

@@ -3,6 +3,7 @@
 
 from __future__ import print_function
 
+import itertools
 import os
 import shutil
 import time
@@ -238,20 +239,26 @@ def __init__(self, cache, cache_ttl, *args, **kw):
 
   # Short-circuiting package iterator.
   def package_iterator(self, resolvable, existing=None):
-    iterator = Iterator(fetchers=[Fetcher([self.__cache])])
-    packages = self.filter_packages_by_interpreter(
-        resolvable.compatible(iterator), self._interpreter, self._platform)
-
-    if packages:
-      if resolvable.exact:
-        return packages
-
-      if self.__cache_ttl:
-        packages = self.filter_packages_by_ttl(packages, self.__cache_ttl)
-        if packages:
+    packages = []
+    if self.__cache_ttl or resolvable.exact:
+      iterator = Iterator(fetchers=[Fetcher([self.__cache])])
+      packages = self.filter_packages_by_interpreter(
+        resolvable.compatible(iterator),
+        self._interpreter,
+        self._platform
+      )
+
+      if packages:
+        if resolvable.exact:
           return packages
 
-    return super(CachingResolver, self).package_iterator(resolvable, existing=existing)
+        if self.__cache_ttl:
+          packages = self.filter_packages_by_ttl(packages, self.__cache_ttl)
+
+    return itertools.chain(
+      packages,
+      super(CachingResolver, self).package_iterator(resolvable, existing=existing)
+    )
 
   # Caching sandwich.
   def build(self, package, options):

tests/test_resolver.py

@@ -7,6 +7,7 @@
 from twitter.common.contextutil import temporary_dir
 
 from pex.common import safe_copy
+from pex.crawler import Crawler
 from pex.fetcher import Fetcher
 from pex.package import EggPackage, SourcePackage
 from pex.resolvable import ResolvableRequirement
@@ -48,6 +49,29 @@ def test_diamond_local_resolve_cached():
       assert len(dists) == 2
 
 
+def test_cached_dependency_pinned_unpinned_resolution_multi_run():
+  # This exercises the issue described here: https://github.com/pantsbuild/pex/issues/178
+  project1_0_0 = make_sdist(name='project', version='1.0.0')
+  project1_1_0 = make_sdist(name='project', version='1.1.0')
+
+  with temporary_dir() as td:
+    for sdist in (project1_0_0, project1_1_0):
+      safe_copy(sdist, os.path.join(td, os.path.basename(sdist)))
+    fetchers = [Fetcher([td])]
+    with temporary_dir() as cd:
+      # First run, pinning 1.0.0 in the cache
+      dists = resolve(['project', 'project==1.0.0'], fetchers=fetchers, cache=cd, cache_ttl=1000)
+      assert len(dists) == 1
+      assert dists[0].version == '1.0.0'
+      # This simulates separate invocations of pex but allows us to keep the same tmp cache dir
+      Crawler.reset_cache()
+      # Second, run, the unbounded 'project' req will find the 1.0.0 in the cache. But should also
+      # return SourcePackages found in td
+      dists = resolve(['project', 'project==1.1.0'], fetchers=fetchers, cache=cd, cache_ttl=1000)
+      assert len(dists) == 1
+      assert dists[0].version == '1.1.0'
+
+
 def test_resolve_prereleases():
   stable_dep = make_sdist(name='dep', version='2.0.0')
   prerelease_dep = make_sdist(name='dep', version='3.0.0rc3')