add test for recent fix for buildout

src/zc/buildout/buildout.py

@@ -392,7 +392,8 @@ class Buildout(UserDict.DictMixin):
         ws = pkg_resources.WorkingSet(entries)
         ws.require('zc.buildout')
         partsdir = os.path.join(options['parts-directory'], 'buildout')
-        os.mkdir(partsdir)
+        if not os.path.exists(partsdir):
+            os.mkdir(partsdir)
         zc.buildout.easy_install.sitepackage_safe_scripts(
             options['bin-directory'], ws, options['executable'], partsdir,
             reqs=['zc.buildout'])
@@ -565,7 +566,7 @@ class Buildout(UserDict.DictMixin):
                 if installed_files is None:
                     self._logger.warning(
                         "The %s install returned None.  A path or "
-                        "iterable os paths should be returned.",
+                        "iterable of paths should be returned.",
                         part)
                     installed_files = ()
                 elif isinstance(installed_files, str):

src/zc/buildout/testing.py

@@ -244,7 +244,7 @@ def set_installer_values(values):
     for name, value in values.items():
         getattr(zc.buildout.easy_install, name)(value)
 
-def make_buildout():
+def make_buildout(executable=None):
     """Make a buildout that uses this version of zc.buildout."""
     # Create a basic buildout.cfg to avoid a warning from buildout.
     open('buildout.cfg', 'w').write(
@@ -254,13 +254,16 @@ def make_buildout():
     # a Buildout will force the Buildout's defaults on the installer).
     installer_values = get_installer_values()
     # Use the buildout bootstrap command to create a buildout
+    config = [
+        ('buildout', 'log-level', 'WARNING'),
+        # trick bootstrap into putting the buildout develop egg
+        # in the eggs dir.
+        ('buildout', 'develop-eggs-directory', 'eggs'),
+        ]
+    if executable is not None:
+        config.append(('buildout', 'executable', executable))
     zc.buildout.buildout.Buildout(
-        'buildout.cfg',
-        [('buildout', 'log-level', 'WARNING'),
-         # trick bootstrap into putting the buildout develop egg
-         # in the eggs dir.
-         ('buildout', 'develop-eggs-directory', 'eggs'),
-         ],
+        'buildout.cfg', config,
         user_defaults=False,
         ).bootstrap([])
     # Create the develop-eggs dir, which didn't get created the usual

src/zc/buildout/tests.py

@@ -2254,6 +2254,94 @@ include-site-packages.
 
     """
 
+def bootstrap_makes_buildout_that_works_with_system_python():
+    """
+In order to work smoothly with a system Python, bootstrapping creates
+the buildout script with
+zc.buildout.easy_install.sitepackage_safe_scripts. If it did not, a
+variety of problems might happen.  For instance, if another version of
+buildout or setuptools is installed in the site-packages than is
+desired, it may cause a problem.
+
+A problem actually experienced in the field is when
+a recipe wants a different version of a dependency that is installed in
+site-packages.  We will create a similar situation, and show that it is now
+handled.
+
+First let's write a dummy recipe.
+
+    >>> mkdir(sample_buildout, 'recipes')
+    >>> write(sample_buildout, 'recipes', 'dummy.py',
+    ... '''
+    ... import logging, os, zc.buildout
+    ...
+    ... class Dummy:
+    ...
+    ...     def __init__(self, buildout, name, options):
+    ...         pass
+    ...
+    ...     def install(self):
+    ...         return ()
+    ...
+    ...     def update(self):
+    ...         pass
+    ... ''')
+    >>> write(sample_buildout, 'recipes', 'setup.py',
+    ... '''
+    ... from setuptools import setup
+    ...
+    ... setup(
+    ...     name = "recipes",
+    ...     entry_points = {'zc.buildout': ['dummy = dummy:Dummy']},
+    ...     install_requires = 'demoneeded==1.2c1',
+    ...     )
+    ... ''')
+    >>> write(sample_buildout, 'recipes', 'README.txt', " ")
+
+Now we'll try to use it with a Python that has a different version of
+demoneeded installed.
+
+    >>> py_path, site_packages_path = make_py()
+    >>> create_sample_sys_install(site_packages_path)
+    >>> rmdir('develop-eggs')
+    >>> from zc.buildout.testing import make_buildout
+    >>> make_buildout(executable=py_path)
+    >>> write(sample_buildout, 'buildout.cfg',
+    ... '''
+    ... [buildout]
+    ... develop = recipes
+    ... parts = dummy
+    ... find-links = %(link_server)s
+    ... executable = %(py_path)s
+    ...
+    ... [dummy]
+    ... recipe = recipes:dummy
+    ... ''' % globals())
+
+Now we actually run the buildout.  Before the change, we got the following
+error:
+
+    Develop: '/sample-buildout/recipes'
+    While:
+      Installing.
+      Getting section dummy.
+      Initializing section dummy.
+      Installing recipe recipes.
+    Error: There is a version conflict.
+    We already have: demoneeded 1.1
+    but recipes 0.0.0 requires 'demoneeded==1.2c1'.
+
+Now, it is handled smoothly.
+
+    >>> print system(buildout)
+    Develop: '/sample-buildout/recipes'
+    Getting distribution for 'demoneeded==1.2c1'.
+    Got demoneeded 1.2c1.
+    Installing dummy.
+    <BLANKLINE>
+
+    """
+
 if sys.version_info > (2, 4):
     def test_exit_codes():
         """