Backed out changeset: ef949e6e6de1, which was itself a backout of the fix for Distribute #323, so this backout restores that fix and also Fixes #141.

3 files changed, 135 insertions, 50 deletions

diff --git a/pkg_resources.py b/pkg_resources.py
index 4bc05e57..bde30989 100644
--- a/pkg_resources.py
+++ b/pkg_resources.py
@@ -504,7 +504,7 @@ class WorkingSet(object):
                     seen[key]=1
                     yield self.by_key[key]
 
-    def add(self, dist, entry=None, insert=True):
+    def add(self, dist, entry=None, insert=True, replace=False):
         """Add `dist` to working set, associated with `entry`
 
         If `entry` is unspecified, it defaults to the ``.location`` of `dist`.
@@ -512,8 +512,9 @@ class WorkingSet(object):
         set's ``.entries`` (if it wasn't already present).
 
         `dist` is only added to the working set if it's for a project that
-        doesn't already have a distribution in the set.  If it's added, any
-        callbacks registered with the ``subscribe()`` method will be called.
+        doesn't already have a distribution in the set, unless `replace=True`.
+        If it's added, any callbacks registered with the ``subscribe()`` method
+        will be called.
         """
         if insert:
             dist.insert_on(self.entries, entry)
@@ -522,7 +523,7 @@ class WorkingSet(object):
             entry = dist.location
         keys = self.entry_keys.setdefault(entry,[])
         keys2 = self.entry_keys.setdefault(dist.location,[])
-        if dist.key in self.by_key:
+        if not replace and dist.key in self.by_key:
             return      # ignore hidden distros
 
         self.by_key[dist.key] = dist
@@ -532,7 +533,8 @@ class WorkingSet(object):
             keys2.append(dist.key)
         self._added_new(dist)
 
-    def resolve(self, requirements, env=None, installer=None):
+    def resolve(self, requirements, env=None, installer=None,
+            replace_conflicting=False):
         """List all distributions needed to (recursively) meet `requirements`
 
         `requirements` must be a sequence of ``Requirement`` objects.  `env`,
@@ -542,6 +544,12 @@ class WorkingSet(object):
         will be invoked with each requirement that cannot be met by an
         already-installed distribution; it should return a ``Distribution`` or
         ``None``.
+
+        Unless `replace_conflicting=True`, raises a VersionConflict exception if
+        any requirements are found on the path that have the correct name but
+        the wrong version.  Otherwise, if an `installer` is supplied it will be
+        invoked to obtain the correct version of the requirement and activate
+        it.
         """
 
         requirements = list(requirements)[::-1]  # set up the stack
@@ -558,10 +566,18 @@ class WorkingSet(object):
             if dist is None:
                 # Find the best distribution and add it to the map
                 dist = self.by_key.get(req.key)
-                if dist is None:
+                if dist is None or (dist not in req and replace_conflicting):
+                    ws = self
                     if env is None:
-                        env = Environment(self.entries)
-                    dist = best[req.key] = env.best_match(req, self, installer)
+                        if dist is None:
+                            env = Environment(self.entries)
+                        else:
+                            # Use an empty environment and workingset to avoid
+                            # any further conflicts with the conflicting
+                            # distribution
+                            env = Environment([])
+                            ws = WorkingSet([])
+                    dist = best[req.key] = env.best_match(req, ws, installer)
                     if dist is None:
                         #msg = ("The '%s' distribution was not found on this "
                         #       "system, and is required by this application.")
@@ -1811,6 +1827,7 @@ def register_namespace_handler(importer_type, namespace_handler):
 
 def _handle_ns(packageName, path_item):
     """Ensure that named package includes a subpath of path_item (if needed)"""
+
     importer = get_importer(path_item)
     if importer is None:
         return None
@@ -1825,12 +1842,14 @@ def _handle_ns(packageName, path_item):
     elif not hasattr(module,'__path__'):
         raise TypeError("Not a package:", packageName)
     handler = _find_adapter(_namespace_handlers, importer)
-    subpath = handler(importer,path_item,packageName,module)
+    subpath = handler(importer, path_item, packageName, module)
     if subpath is not None:
         path = module.__path__
         path.append(subpath)
         loader.load_module(packageName)
-        module.__path__ = path
+        for path_item in path:
+            if path_item not in module.__path__:
+                module.__path__.append(path_item)
     return subpath
 
 def declare_namespace(packageName):
diff --git a/setuptools/dist.py b/setuptools/dist.py
index 3126cb96..0801ae74 100644
--- a/setuptools/dist.py
+++ b/setuptools/dist.py
@@ -260,9 +260,10 @@ class Distribution(_Distribution):
         """Resolve pre-setup requirements"""
         from pkg_resources import working_set, parse_requirements
         for dist in working_set.resolve(
-            parse_requirements(requires), installer=self.fetch_build_egg
+            parse_requirements(requires), installer=self.fetch_build_egg,
+            replace_conflicting=True
         ):
-            working_set.add(dist)
+            working_set.add(dist, replace=True)
 
     def finalize_options(self):
         _Distribution.finalize_options(self)
diff --git a/setuptools/tests/test_easy_install.py b/setuptools/tests/test_easy_install.py
index a90ae23f..8c797d55 100644
--- a/setuptools/tests/test_easy_install.py
+++ b/setuptools/tests/test_easy_install.py
@@ -19,8 +19,10 @@ from setuptools.command.easy_install import (
 from setuptools.command.easy_install import PthDistributions
 from setuptools.command import easy_install as easy_install_pkg
 from setuptools.dist import Distribution
+from pkg_resources import working_set, VersionConflict
 from pkg_resources import Distribution as PRDistribution
 import setuptools.tests.server
+import pkg_resources
 
 class FakeDist(object):
     def get_entry_map(self, group):
@@ -230,47 +232,15 @@ class TestUserInstallTest(unittest.TestCase):
         SandboxViolation.
         """
 
-        test_setup_attrs = {
-            'name': 'test_pkg', 'version': '0.0',
-            'setup_requires': ['foobar'],
-            'dependency_links': [os.path.abspath(self.dir)]
-        }
-
-        test_pkg = os.path.join(self.dir, 'test_pkg')
+        test_pkg = create_setup_requires_package(self.dir)
         test_setup_py = os.path.join(test_pkg, 'setup.py')
-        os.mkdir(test_pkg)
-
-        f = open(test_setup_py, 'w')
-        f.write(textwrap.dedent("""\
-            import setuptools
-            setuptools.setup(**%r)
-        """ % test_setup_attrs))
-        f.close()
 
-        foobar_path = os.path.join(self.dir, 'foobar-0.1.tar.gz')
-        make_trivial_sdist(
-            foobar_path,
-            textwrap.dedent("""\
-                import setuptools
-                setuptools.setup(
-                    name='foobar',
-                    version='0.1'
-                )
-            """))
-
-        old_stdout = sys.stdout
-        old_stderr = sys.stderr
-        sys.stdout = StringIO()
-        sys.stderr = StringIO()
         try:
-            try:
+            with quiet_context():
                 with reset_setup_stop_context():
                     run_setup(test_setup_py, ['install'])
-            except SandboxViolation:
-                self.fail('Installation caused SandboxViolation')
-        finally:
-            sys.stdout = old_stdout
-            sys.stderr = old_stderr
+        except SandboxViolation:
+            self.fail('Installation caused SandboxViolation')
 
 
 class TestSetupRequires(unittest.TestCase):
@@ -290,8 +260,10 @@ class TestSetupRequires(unittest.TestCase):
             # Some platforms (Jython) don't find a port to which to bind,
             #  so skip this test for them.
             return
-        # create an sdist that has a build-time dependency.
-        with TestSetupRequires.create_sdist() as dist_file:
+        with quiet_context():
+          # TODO: correct indentation here
+          # create an sdist that has a build-time dependency.
+          with TestSetupRequires.create_sdist() as dist_file:
             with tempdir_context() as temp_install_dir:
                 with environment_context(PYTHONPATH=temp_install_dir):
                     ei_params = ['--index-url', p_index.url,
@@ -330,6 +302,81 @@ class TestSetupRequires(unittest.TestCase):
                 """).lstrip())
             yield dist_path
 
+    def test_setup_requires_overrides_version_conflict(self):
+        """
+        Regression test for issue #323.
+
+        Ensures that a distribution's setup_requires requirements can still be
+        installed and used locally even if a conflicting version of that
+        requirement is already on the path.
+        """
+
+        pr_state = pkg_resources.__getstate__()
+        fake_dist = PRDistribution('does-not-matter', project_name='foobar',
+                                   version='0.0')
+        working_set.add(fake_dist)
+
+        def setup_and_run(temp_dir):
+            test_pkg = create_setup_requires_package(temp_dir)
+            test_setup_py = os.path.join(test_pkg, 'setup.py')
+            try:
+                stdout, stderr = quiet_context(
+                    lambda: reset_setup_stop_context(
+                        # Don't even need to install the package, just running
+                        # the setup.py at all is sufficient
+                        lambda: run_setup(test_setup_py, ['--name'])
+                ))
+            except VersionConflict:
+                self.fail('Installing setup.py requirements caused '
+                          'VersionConflict')
+
+            lines = stdout.splitlines()
+            self.assertTrue(len(lines) > 0)
+            self.assertTrue(lines[-1].strip(), 'test_pkg')
+
+        try:
+            tempdir_context(setup_and_run)
+        finally:
+            pkg_resources.__setstate__(pr_state)
+
+
+def create_setup_requires_package(path):
+    """Creates a source tree under path for a trivial test package that has a
+    single requirement in setup_requires--a tarball for that requirement is
+    also created and added to the dependency_links argument.
+    """
+
+    test_setup_attrs = {
+        'name': 'test_pkg', 'version': '0.0',
+        'setup_requires': ['foobar==0.1'],
+        'dependency_links': [os.path.abspath(path)]
+    }
+
+    test_pkg = os.path.join(path, 'test_pkg')
+    test_setup_py = os.path.join(test_pkg, 'setup.py')
+    test_setup_cfg = os.path.join(test_pkg, 'setup.cfg')
+    os.mkdir(test_pkg)
+
+    f = open(test_setup_py, 'w')
+    f.write(textwrap.dedent("""\
+        import setuptools
+        setuptools.setup(**%r)
+    """ % test_setup_attrs))
+    f.close()
+
+    foobar_path = os.path.join(path, 'foobar-0.1.tar.gz')
+    make_trivial_sdist(
+        foobar_path,
+        textwrap.dedent("""\
+            import setuptools
+            setuptools.setup(
+                name='foobar',
+                version='0.1'
+            )
+        """))
+
+    return test_pkg
+
 
 def make_trivial_sdist(dist_path, setup_py):
     """Create a simple sdist tarball at dist_path, containing just a
@@ -392,3 +439,21 @@ def reset_setup_stop_context():
     distutils.core._setup_stop_after = None
     yield
     distutils.core._setup_stop_after = setup_stop_after
+
+
+@contextlib.contextmanager
+def quiet_context():
+    """
+    Redirect stdout/stderr to StringIO objects to prevent console output from
+    distutils commands.
+    """
+
+    old_stdout = sys.stdout
+    old_stderr = sys.stderr
+    new_stdout = sys.stdout = StringIO.StringIO()
+    new_stderr = sys.stderr = StringIO.StringIO()
+    try:
+        yield new_stdout, new_stderr
+    finally:
+        sys.stdout = old_stdout
+        sys.stderr = old_stderr