swc-installation-test-2.py: Convert PathCommandDependency to VersionP…

…listCommandDependency

Philip Guo suggested using version.plist to lookup the version number
for applications on OS X [1].  Searching around, I found an example of
Safari's version.plist posted by ASmit010 [2]:

  <?xml version="1.0" encoding="UTF-8"?>
  <!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
  <plist version="1.0">
  <dict>
       <key>BuildVersion</key>
       <string>1</string>
       <key>CFBundleShortVersionString</key>
       <string>5.1.7</string>
       <key>CFBundleVersion</key>
       <string>7534.57.2</string>
       <key>ProjectName</key>
       <string>WebBrowser</string>
       <key>SourceVersion</key>
       <string>7534057002000000</string>
  </dict>
  </plist>

Looking at that example, the version information we want is associated
with CFBundleShortVersionString [3]:

  CFBundleShortVersionString (String - iOS, OS X) specifies the
  release version number of the bundle, which identifies a released
  iteration of the app. The release version number is a string
  comprised of three period-separated integers. The first integer
  represents major revisions to the app, such as revisions that
  implement new features or major changes. The second integer denotes
  revisions that implement less prominent features. The third integer
  represents maintenance releases.

  The value for this key differs from the value for CFBundleVersion,
  which identifies an iteration (released or unreleased) of the
  app. This key can be localized by including it in your
  InfoPlist.strings files

The sibling-entries for keys and values are a bit awkward using
Python's stock ElementTree [4,5], which doesn't have built-in methods
for finding parents or siblings [6].  I've followed the example set by
lxml and added _get_parent and _get_next helpers (mirroring getparent
[7] and getnext [8]) to make it the logic in _get_version_from_plist
more clear.

[1]: https://twitter.com/pgbovine/status/559094439009075203
[2]: https://discussions.apple.com/message/19757845#19757845
[3]: https://developer.apple.com/library/ios/documentation/General/Reference/InfoPlistKeyReference/Articles/CoreFoundationKeys.html#//apple_ref/doc/uid/20001431-111349
[4]: https://docs.python.org/2/library/xml.etree.elementtree.html
[5]: https://docs.python.org/3/library/xml.etree.elementtree.html
[6]: http://lxml.de/1.3/api.html#trees-and-documents
[7]: http://lxml.de/api/lxml.etree._Element-class.html#getparent
[8]: http://lxml.de/api/lxml.etree._Element-class.html#getnext

swc-installation-test-2.py

@@ -50,6 +50,7 @@ def import_module(name):
     import urllib.parse as _urllib_parse
 except ImportError:  # Python 2.x
     import urllib as _urllib_parse  # for quote()
+import xml.etree.ElementTree as _element_tree
 
 
 if not hasattr(_shlex, 'quote'):  # Python versions older than 3.3
@@ -477,26 +478,62 @@ def _get_version(self):
         return match.group(1)
 
 
-class PathCommandDependency (CommandDependency):
+class VersionPlistCommandDependency (CommandDependency):
     """A command that doesn't support --version or equivalent options
 
-    On some operating systems (e.g. OS X), a command's executable may
-    be hard to find, or not exist in the PATH.  Work around that by
-    just checking for the existence of a characteristic file or
-    directory.  Since the characteristic path may depend on OS,
-    installed version, etc., take a list of paths, and succeed if any
-    of them exists.
+    On OS X, a command's executable may be hard to find, or not exist
+    in the PATH.  Work around that by looking up the version
+    information in the package's version.plist file.
     """
+    def __init__(self, key='CFBundleShortVersionString', **kwargs):
+        super(VersionPlistCommandDependency, self).__init__(**kwargs)
+        self.key = key
+
     def _get_command_version_stream(self, *args, **kwargs):
         raise NotImplementedError()
 
     def _get_version_stream(self, *args, **kwargs):
         raise NotImplementedError()
 
+    @staticmethod
+    def _get_parent(root, element):
+        """Returns the parent of this element or None for the root element
+        """
+        for node in root.iter():
+            if element in node:
+                return node
+        raise ValueError((root, element))
+
+    @staticmethod
+    def _get_next(root, element):
+        """Returns the following sibling of this element or None
+        """
+        parent = self._get_parent(root=root, element=element)
+        siblings = iter(parent)
+        for node in siblings:
+            if node == element:
+                try:
+                    return next(siblings)
+                except StopIteration:
+                    return None
+        return None
+
+    def _get_version_from_plist(self, path):
+        """Parse the plist and return the value string for self.key
+        """
+        tree = _element_tree.parse(source=path)
+        data = {}
+        for key in tree.findall('.//key'):
+            value = self._get_next(root=tree, element=key)
+            if value.tag != 'string':
+                raise ValueError((tree, key, value))
+            data[key.text] = value.text
+        return data[self.key]
+
     def _get_version(self):
         for path in self.paths:
             if _os.path.exists(path):
-                return None
+                return self._get_version_from_plist(path=path)
         raise DependencyError(
             checker=self,
             message=(
@@ -746,23 +783,28 @@ def _program_files_paths(*args):
 
 
 for paths,name,long_name in [
-        ([_os.path.join(_ROOT_PATH, 'Applications', 'Sublime Text 2.app')],
+        ([_os.path.join(_ROOT_PATH, 'Applications', 'Sublime Text 2.app',
+                        'Contents', 'version.plist')],
          'sublime-text', 'Sublime Text'),
-        ([_os.path.join(_ROOT_PATH, 'Applications', 'TextMate.app')],
+        ([_os.path.join(_ROOT_PATH, 'Applications', 'TextMate.app',
+                        'Contents', 'version.plist')],
          'textmate', 'TextMate'),
-        ([_os.path.join(_ROOT_PATH, 'Applications', 'TextWrangler.app')],
+        ([_os.path.join(_ROOT_PATH, 'Applications', 'TextWrangler.app',
+                        'Contents', 'version.plist')],
          'textwrangler', 'TextWrangler'),
-        ([_os.path.join(_ROOT_PATH, 'Applications', 'Safari.app')],
+        ([_os.path.join(_ROOT_PATH, 'Applications', 'Safari.app',
+                        'Contents', 'version.plist')],
          'safari', 'Safari'),
-        ([_os.path.join(_ROOT_PATH, 'Applications', 'Xcode.app'),  # OS X >=1.7
-          _os.path.join(_ROOT_PATH, 'Developer', 'Applications', 'Xcode.app'
-                        )  # OS X 1.6,
+        ([_os.path.join(_ROOT_PATH, 'Applications', 'Xcode.app',
+                        'Contents', 'version.plist'),  # OS X >=1.7
+          _os.path.join(_ROOT_PATH, 'Developer', 'Applications', 'Xcode.app',
+                        'Contents', 'version.plist'),  # OS X 1.6,
           ],
          'xcode', 'Xcode'),
         ]:
     if not long_name:
         long_name = name
-    CHECKER[name] = PathCommandDependency(
+    CHECKER[name] = VersionPlistCommandDependency(
         command=None, paths=paths, name=name, long_name=long_name)
 del paths, name, long_name  # cleanup namespace
 
@@ -807,9 +849,10 @@ def _program_files_paths(*args):
                          long_name='{0} for IPython'.format(
                              CHECKER['chromium'].long_name),
                          minimum_version=(13, 0)),
-                     PathCommandDependency(
+                     VersionPlistCommandDependency(
                          command=CHECKER['safari'].command,
                          paths=CHECKER['safari'].paths,
+                         key=CHECKER['safari'].key,
                          name='{0}-for-ipython'.format(
                              CHECKER['safari'].name),
                          long_name='{0} for IPython'.format(