Fixes #326

Fixed a bug introduced in 2.6.0:
zc.buildout and its dependeoncies were reported as picked even when
their versions were fixed in a ``versions`` section.  Worse, when the
``update-versions-file`` option was used, the ``versions`` section was
updated needlessly on every run.

CHANGES.rst

@@ -4,7 +4,11 @@ Change History
 2.7.1 (unreleased)
 ==================
 
-- Nothing changed yet.
+- Fixed a bug introduced in 2.6.0:
+  zc.buildout and its dependeoncies were reported as picked even when
+  their versions were fixed in a ``versions`` section.  Worse, when the
+  ``update-versions-file`` option was used, the ``versions`` section was
+  updated needlessly on every run.
 
 
 2.7.0 (2017-01-30)

src/zc/buildout/easy_install.py

@@ -558,23 +558,25 @@ class Installer:
                                                      self._links,
                                                      self._allow_hosts)
 
-        for dist in dists:
+        if self._dest is not None:
             # Check whether we picked a version and, if we did, report it:
-            if not (
-                dist.precedence == pkg_resources.DEVELOP_DIST
-                or
-                (len(requirement.specs) == 1
-                 and
-                 requirement.specs[0][0] == '==')
-                ):
-                logger.debug('Picked: %s = %s',
-                             dist.project_name, dist.version)
-                self._picked_versions[dist.project_name] = dist.version
-
-                if not self._allow_picked_versions:
-                    raise zc.buildout.UserError(
-                        'Picked: %s = %s' % (dist.project_name, dist.version)
-                        )
+            for dist in dists:
+                if not (
+                    dist.precedence == pkg_resources.DEVELOP_DIST
+                    or
+                    (len(requirement.specs) == 1
+                     and
+                     requirement.specs[0][0] == '==')
+                    ):
+                    logger.debug('Picked: %s = %s',
+                                 dist.project_name, dist.version)
+                    self._picked_versions[dist.project_name] = dist.version
+
+                    if not self._allow_picked_versions:
+                        raise zc.buildout.UserError(
+                            'Picked: %s = %s' % (dist.project_name,
+                                                 dist.version)
+                            )
 
         return dists
 

src/zc/buildout/repeatable.txt

@@ -420,10 +420,8 @@ The versions file now contains the extra pin:
 
 And re-running buildout doesn't report any picked versions anymore:
 
-    >>> print_(system(buildout), end='') # doctest: +ELLIPSIS
-    Updating foo.
-    recipe v2
-    ...
+    >>> 'picked' in system(buildout)
+    False
 
 If you've enabled ``update-versions-file`` but not ``show-picked-versions``,
 buildout will append the versions to your versions file anyway (without

src/zc/buildout/tests.py

@@ -2408,12 +2408,12 @@ def wont_downgrade_due_to_prefer_final():
     ... parts =
     ... ''')
 
-    >>> [v] = [l.split('= >=', 1)[1].strip()
+    >>> [v] = [str(l.split('= >=', 1)[1].strip())
     ...        for l in system(buildout+' -vv').split('\n')
     ...        if l.startswith('zc.buildout = >=')]
-    >>> v == pkg_resources.working_set.find(
+    >>> v == str(pkg_resources.working_set.find(
     ...         pkg_resources.Requirement.parse('zc.buildout')
-    ...         ).version
+    ...         ).version)
     True
 
     >>> write('buildout.cfg',
@@ -3062,6 +3062,39 @@ def test_abi_tag_eggs():
     ...
     """
 
+def test_buildout_doesnt_keep_adding_itself_to_versions():
+    r"""
+    We were constantly writing to versions.cfg for buildout and setuptools
+
+    >>> write('buildout.cfg',
+    ... '''
+    ... [buildout]
+    ... parts =
+    ... extends = versions.cfg
+    ... show-picked-versions = true
+    ... update-versions-file = versions.cfg
+    ... extends = versions.cfg
+    ... ''')
+    >>> write('versions.cfg',
+    ... '''[versions]
+    ... ''')
+    >>> _ = system(join('bin', 'buildout'))
+    >>> with open('versions.cfg') as f:
+    ...     versions = f.read()
+    >>> _ = system(join('bin', 'buildout'))
+    >>> _ = system(join('bin', 'buildout'))
+    >>> _ = system(join('bin', 'buildout'))
+    >>> with open('versions.cfg') as f:
+    ...     versions == f.read()
+    True
+    >>> cat('versions.cfg') # doctest: +ELLIPSIS
+    [versions]
+    <BLANKLINE>
+    # Added by buildout...
+    setuptools = 34.0.3
+    ...
+    """
+
 if sys.platform == 'win32':
     del buildout_honors_umask # umask on dohs is academic