Make sure (???) buildout doesn't downgrade due to defer-final

src/zc/buildout/buildout.py

@@ -287,6 +287,7 @@ class Buildout(DictMixin):
         self.newest = (newest == 'true')
 
         versions = {}
+        self.versions = versions
         versions_section = options.get('versions')
         if versions_section:
             versions.update(dict(self[versions_section]))
@@ -854,6 +855,16 @@ class Buildout(DictMixin):
         if not self.newest:
             return
 
+        # Prevent downgrading due to prefer-final:
+        options = self['buildout']
+        if not ('zc.buildout-version' in options
+                or
+                'zc.buildout' in self.versions):
+            v = pkg_resources.working_set.find(
+                pkg_resources.Requirement.parse('zc.buildout')
+                ).version
+            options['zc.buildout-version'] = '>=' + v
+
         ws = zc.buildout.easy_install.install(
             [
             (spec + ' ' + self['buildout'].get(spec+'-version', '')).strip()

src/zc/buildout/buildout.txt

@@ -2261,7 +2261,7 @@ database is shown.
     ... """)
 
     >>> print_(system(buildout+' -vv'), end='') # doctest: +NORMALIZE_WHITESPACE
-    Installing 'zc.buildout', 'distribute'.
+    Installing 'zc.buildout >=1.9a1', 'distribute'.
     We have a develop egg: zc.buildout 1.0.0.
     We have the best distribution that satisfies 'distribute'.
     Picked: distribute = 0.6
@@ -2289,6 +2289,7 @@ database is shown.
     socket-timeout =
     use-dependency-links = true
     verbosity = 20
+    zc.buildout-version = >=1.9a1
     <BLANKLINE>
 
 All of these options can be overridden by configuration files or by

src/zc/buildout/repeatable.txt

@@ -128,7 +128,7 @@ about versions used. If we run the buildout in verbose mode without
 specifying a versions section:
 
     >>> print_(system(buildout+' buildout:versions= -v'), end='')
-    Installing 'zc.buildout', 'distribute'.
+    Installing 'zc.buildout >=1.99', 'distribute'.
     We have a develop egg: zc.buildout 1.0.0.
     We have the best distribution that satisfies 'distribute'.
     Picked: distribute = 0.6
@@ -150,7 +150,7 @@ that we can fix them in a versions section.
 If we run the buildout with the versions section:
 
     >>> print_(system(buildout+' -v'), end='')
-    Installing 'zc.buildout', 'distribute'.
+    Installing 'zc.buildout >=1.99', 'distribute'.
     We have a develop egg: zc.buildout 1.0.0.
     We have the best distribution that satisfies 'distribute'.
     Picked: distribute = 0.6

src/zc/buildout/tests.py

@@ -330,7 +330,7 @@ if we hadn't required sampley ourselves:
 If we use the verbose switch, we can see where requirements are coming from:
 
     >>> print_(system(buildout+' -v'), end='') # doctest: +ELLIPSIS
-    Installing 'zc.buildout', 'distribute'.
+    Installing 'zc.buildout >=1.99', 'distribute'.
     We have a develop egg: zc.buildout 1.0.0
     We have the best distribution that satisfies 'distribute'.
     Picked: distribute = 0.6
@@ -527,7 +527,7 @@ def create_sections_on_command_line():
 
     >>> print_(system(buildout + ' foo:bar=1 -vv'), end='')
     ...        # doctest: +ELLIPSIS
-    Installing 'zc.buildout', 'distribute'.
+    Installing 'zc.buildout >=1.99', 'distribute'.
     ...
     [foo]
     bar = 1
@@ -1946,7 +1946,7 @@ def dealing_with_extremely_insane_dependencies():
     However, if we run in verbose mode, we can see why packages were included:
 
     >>> print_(system(buildout+' -v'), end='') # doctest: +ELLIPSIS
-    Installing 'zc.buildout', 'distribute'.
+    Installing 'zc.buildout >=1.99', 'distribute'.
     We have a develop egg: zc.buildout 1.0.0
     We have the best distribution that satisfies 'distribute'.
     Picked: distribute = 0.6
@@ -2227,7 +2227,7 @@ The default is prefer-final = true:
     ... ''' % globals())
 
     >>> print_(system(buildout+' -v'), end='') # doctest: +ELLIPSIS
-    Installing 'zc.buildout', 'distribute'.
+    Installing 'zc.buildout >=1.99', 'distribute'.
     ...
     Picked: demo = 0.3
     ...
@@ -2249,7 +2249,7 @@ We get the same behavior if we add prefer-final = true
     ... ''' % globals())
 
     >>> print_(system(buildout+' -v'), end='') # doctest: +ELLIPSIS
-    Installing 'zc.buildout', 'distribute'.
+    Installing 'zc.buildout >=1.99', 'distribute'.
     ...
     Picked: demo = 0.3
     ...
@@ -2271,7 +2271,7 @@ distributions:
     ... ''' % globals())
 
     >>> print_(system(buildout+' -v'), end='') # doctest: +ELLIPSIS
-    Installing 'zc.buildout', 'distribute'.
+    Installing 'zc.buildout >=1.99', 'distribute'.
     ...
     Picked: demo = 0.4c1
     ...
@@ -2295,6 +2295,50 @@ We get an error if we specify anything but true or false:
     While:
       Initializing.
     Error: Invalid value for prefer-final option: no
+    """
+
+def wont_downgrade_due_to_prefer_final():
+    r"""
+    If we install a non-final buildout version, we don't want to
+    downgrade just bcause we prefer-final.  If a buildout version
+    isn't specified, either through buildout-version or a versions
+    entry, then buildout-version gets set to >=CURRENT_VERSION.
+
+    >>> write('buildout.cfg',
+    ... '''
+    ... [buildout]
+    ... parts =
+    ... ''')
+    >>> [v] = [l.split('=', 1)[1].strip()
+    ...        for l in system(buildout+' -vv').split('\n')
+    ...        if l.startswith('zc.buildout-version = ')]
+    >>> v == '>=' + pkg_resources.working_set.find(
+    ...         pkg_resources.Requirement.parse('zc.buildout')
+    ...         ).version
+    True
+
+    >>> write('buildout.cfg',
+    ... '''
+    ... [buildout]
+    ... parts =
+    ... zc.buildout-version = >.1
+    ... ''')
+    >>> [l.split('=', 1)[1].strip()
+    ...        for l in system(buildout+' -vv').split('\n')
+    ...        if l.startswith('zc.buildout-version =')]
+    [u'>.1']
+
+    >>> write('buildout.cfg',
+    ... '''
+    ... [buildout]
+    ... parts =
+    ... versions = versions
+    ... [versions]
+    ... zc.buildout = 43
+    ... ''')
+    >>> print_(system(buildout+' -v'), end='') # doctest: +ELLIPSIS
+    Installing...
+    Error: Couldn't find a distribution for 'zc.buildout==43'.
 
     """
 
@@ -2913,6 +2957,8 @@ def test_suite():
                 zc.buildout.testing.normalize_script,
                 zc.buildout.testing.normalize_egg_py,
                 zc.buildout.testing.not_found,
+                (re.compile(r'zc.buildout-version = >=\S+'), ''),
+                (re.compile(r"Installing 'zc.buildout >=\S+"), ''),
                 (re.compile('__buildout_signature__ = recipes-\S+'),
                  '__buildout_signature__ = recipes-SSSSSSSSSSS'),
                 (re.compile('executable = [\S ]+python\S*', re.I),
@@ -2947,6 +2993,9 @@ def test_suite():
                zc.buildout.testing.normalize_script,
                zc.buildout.testing.normalize_egg_py,
                zc.buildout.testing.not_found,
+               (re.compile(r"Installing 'zc.buildout >=\S+"), ''),
+               (re.compile(r"Getting distribution for 'zc.buildout >=\S+"),
+                ''),
                (re.compile('__buildout_signature__ = recipes-\S+'),
                 '__buildout_signature__ = recipes-SSSSSSSSSSS'),
                (re.compile('[-d]  distribute-\S+[.]egg'), 'distribute.egg'),
@@ -3000,6 +3049,9 @@ def test_suite():
                 zc.buildout.testing.not_found,
                 normalize_bang,
                 normalize_S,
+                (re.compile(r"Installing 'zc.buildout >=\S+"), ''),
+                (re.compile(r"Getting distribution for 'zc.buildout>=\S+"),
+                 ''),
                 (re.compile('99[.]99'), 'NINETYNINE.NINETYNINE'),
                 (re.compile(
                     r'(zc.buildout|distribute)( version)? \d+[.]\d+\S*'),
@@ -3048,7 +3100,7 @@ def test_suite():
                'http://localhost/'),
               (re.compile('[0-9a-f]{32}'), '<MD5 CHECKSUM>'),
               zc.buildout.testing.normalize_path,
-              zc.buildout.testing.ignore_not_upgrading,    
+              zc.buildout.testing.ignore_not_upgrading,
               ]),
             ),
 
@@ -3062,6 +3114,7 @@ def test_suite():
                 zc.buildout.testing.normalize_egg_py,
                 zc.buildout.testing.normalize___pycache__,
                 zc.buildout.testing.not_found,
+                (re.compile(r"Installing 'zc.buildout >=\S+"), 'Installing '),
                 (re.compile(r'^(\w+\.)*(Missing\w+: )'), '\2'),
                 (re.compile("buildout: Running \S*setup.py"),
                  'buildout: Running setup.py'),

src/zc/buildout/update.txt

@@ -66,7 +66,7 @@ Now if we run the buildout, the buildout will upgrade itself to the
 new versions found in new releases:
 
     >>> print_(system(buildout), end='')
-    Getting distribution for 'zc.buildout'.
+    Getting distribution for 'zc.buildout>=1.99'.
     Got zc.buildout 99.99.
     Getting distribution for 'distribute'.
     Got distribute 99.99.
@@ -177,7 +177,7 @@ directory:
     Creating directory '/sample_buildout2/parts'.
     Creating directory '/sample_buildout2/eggs'.
     Creating directory '/sample_buildout2/develop-eggs'.
-    Getting distribution for 'zc.buildout'.
+    Getting distribution for 'zc.buildout>=1.99'.
     Got zc.buildout 99.99.
     Getting distribution for 'distribute'.
     Got distribute 99.99.