Implement draft support for namespace packages, both declaring them

initially and fixing them up when new eggs are added to sys.path.  At the
moment, all namespace packages are fixed up whenever any new egg is added
to sys.path, but this might not scale well if there are lots of eggs and
lots of namespace packages.  Perhaps we should limit namespace fixups to
namespace packages explicitly declared in the egg?

--HG--
branch : setuptools
extra : convert_revision : svn%3A6015fed2-1504-0410-9fe1-9d1591cc4771/sandbox/trunk/setuptools%4041014

pkg_resources.py

@@ -742,7 +742,7 @@ def register_finder(importer_type, distribution_finder):
     """Register `distribution_finder` to find distributions in sys.path items
 
     `importer_type` is the type or class of a PEP 302 "Importer" (sys.path item
-    handler), and `distribution_finder_type` is a callable that, passed a path
+    handler), and `distribution_finder` is a callable that, passed a path
     item and the importer instance, yields ``Distribution`` instances found on
     that path item.  See ``pkg_resources.find_on_path`` for an example."""
     _distribution_finders[importer_type] = distribution_finder
@@ -814,6 +814,129 @@ def find_on_path(importer,path_item):
         yield Distribution.from_filename(path_item, metadata=metadata)
 
 register_finder(ImpWrapper,find_on_path)
+
+
+
+
+_namespace_handlers = {}
+_namespace_packages = {}
+
+def register_namespace_handler(importer_type, namespace_handler):
+    """Register `namespace_handler` to declare namespace packages
+
+    `importer_type` is the type or class of a PEP 302 "Importer" (sys.path item
+    handler), and `namespace_handler` is a callable like this::
+
+        def namespace_handler(importer,path_entry,moduleName,module):
+            # return a path_entry to use for child packages
+
+    Namespace handlers are only called if the importer object has already
+    agreed that it can handle the relevant path item, and they should only
+    return a subpath if the module __path__ does not already contain an
+    equivalent subpath.  For an example namespace handler, see
+    ``pkg_resources.file_ns_handler``.
+    """
+    _namespace_handlers[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)
+    loader = importer.find_module(packageName)
+    if loader is None:
+        return None
+
+    module = sys.modules.get(packageName) or loader.load_module(packageName)
+    if not hasattr(module,'__path__'):
+        raise TypeError("Not a package:", packageName)
+
+    handler = _find_adapter(_distribution_finders, importer)
+    subpath = handler(importer,path_item,packageName,module)
+
+    if subpath is not None:
+        module.__path__.append(subpath)
+
+    return subpath
+
+
+def declare_namespace(packageName):
+    """Declare that package 'packageName' is a namespace package"""
+
+    # XXX nslock.acquire()
+    try:
+        if packageName in _namespace_packages:
+            return
+
+        path, parent = sys.path, None
+        if '.' in packageName:
+            parent = '.'.join(package.split('.')[:-1])
+            declare_namespace(parent)
+            __import__(parent)
+            try:
+                path = sys.modules[parent].__path__
+            except AttributeError:
+                raise TypeError("Not a package:", parent)
+    
+        for path_item in path:
+            # Ensure all the parent's path items are reflected in the child,
+            # if they apply
+            _handle_ns(packageName, path_item)
+    
+        # Track what packages are namespaces, so when new path items are added,
+        # they can be updated
+        _namespace_packages.setdefault(parent,[]).append(packageName)
+        _namespace_packages.setdefault(packageName,[])
+
+    finally:
+        pass # XXX nslock.release()
+
+def fixup_namespace_packages(path_item, parent=None):
+    """Ensure that previously-declared namespace packages include path_item"""
+    # XXX nslock.acquire()
+    try:
+        for package in _namespace_packages.get(parent,()):
+            subpath = _handle_ns(package, path_item)
+            if subpath: fixup_namespace_packages(subpath,package)
+    finally:
+        pass # XXX nslock.release()
+
+def file_ns_handler(importer, path_item, packageName, module):
+    """Compute an ns-package subpath for a filesystem or zipfile importer"""
+
+    subpath = os.path.join(path_item, packageName.split('.')[-1])
+    normalized = os.path.normpath(os.path.normcase(subpath))
+    for item in module.__path__:
+        if os.path.normpath(os.path.normcase(item))==normalized:
+            break
+    else:
+        # Only return the path if it's not already there
+        return subpath
+
+register_namespace_handler(ImpWrapper,file_ns_handler)
+register_namespace_handler(zipimport.zipimporter,file_ns_handler)
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
 
 
 
@@ -988,11 +1111,10 @@ class Distribution(object):
             return self.__dep_map
         except AttributeError:
             dm = self.__dep_map = {None: []}
-            if self.metadata.has_metadata('depends.txt'):
-                for section,contents in split_sections(
-                    self.metadata.get_metadata_lines('depends.txt')
-                ):
-                    dm[section] = list(parse_requirements(contents))
+            for section,contents in split_sections(
+                self._get_metadata('depends.txt')
+            ):
+                dm[section] = list(parse_requirements(contents))
             return dm
 
     _dep_map = property(_dep_map)
@@ -1010,18 +1132,19 @@ class Distribution(object):
                 raise InvalidOption("No such option", self, opt)
         return deps
 
+    def _get_metadata(self,name):
+        if self.metadata.has_metadata(name):
+            for line in self.metadata.get_metadata_lines(name):
+                yield line
+
     def install_on(self,path=None):
-        # XXX this needs to interface with namespace packages and such
+        """Ensure distribution is importable on `path` (default=sys.path)"""
         if path is None: path = sys.path
         if self.path not in path:
             path.append(self.path)
-
-
-def _sort_dists(dists):
-    tmp = [(dist.version,dist) for dist in dists]
-    tmp.sort()
-    dists[::-1] = [d for v,d in tmp]
-
+        if path is sys.path:
+            fixup_namespace_packages(self.path)
+            map(declare_namespace, self._get_metadata('namespace_packages.txt'))
 
 def parse_requirements(strs):
     """Yield ``Requirement`` objects for each specification in `strs`
@@ -1083,10 +1206,10 @@ def parse_requirements(strs):
         yield Requirement(distname.replace('_','-'), specs, options)
 
 
-
-
-
-
+def _sort_dists(dists):
+    tmp = [(dist.version,dist) for dist in dists]
+    tmp.sort()
+    dists[::-1] = [d for v,d in tmp]