Add a namespace module.

CHANGES.rst

@@ -2,6 +2,12 @@
 CHANGES
 =======
 
+v28.7.0
+-------
+
+* Moved much of the namespace package handling functionality
+  into a separate module for re-use in something like #789.
+
 v28.6.1
 -------
 

setuptools/command/install_egg_info.py

@@ -1,14 +1,13 @@
 from distutils import log, dir_util
 import os
 
-from setuptools.extern.six.moves import map
-
 from setuptools import Command
+from setuptools import namespaces
 from setuptools.archive_util import unpack_archive
 import pkg_resources
 
 
-class install_egg_info(Command):
+class install_egg_info(namespaces.Installer, Command):
     """Install an .egg-info directory for the package"""
 
     description = "Install an .egg-info directory for the package"
@@ -61,59 +60,3 @@ def skimmer(src, dst):
             return dst
 
         unpack_archive(self.source, self.target, skimmer)
-
-    def install_namespaces(self):
-        nsp = self._get_all_ns_packages()
-        if not nsp:
-            return
-        filename, ext = os.path.splitext(self.target)
-        filename += '-nspkg.pth'
-        self.outputs.append(filename)
-        log.info("Installing %s", filename)
-        lines = map(self._gen_nspkg_line, nsp)
-
-        if self.dry_run:
-            # always generate the lines, even in dry run
-            list(lines)
-            return
-
-        with open(filename, 'wt') as f:
-            f.writelines(lines)
-
-    _nspkg_tmpl = (
-        "import sys, types, os",
-        "pep420 = sys.version_info > (3, 3)",
-        "p = os.path.join(sys._getframe(1).f_locals['sitedir'], *%(pth)r)",
-        "ie = os.path.exists(os.path.join(p,'__init__.py'))",
-        "m = not ie and not pep420 and "
-            "sys.modules.setdefault(%(pkg)r, types.ModuleType(%(pkg)r))",
-        "mp = (m or []) and m.__dict__.setdefault('__path__',[])",
-        "(p not in mp) and mp.append(p)",
-    )
-    "lines for the namespace installer"
-
-    _nspkg_tmpl_multi = (
-        'm and setattr(sys.modules[%(parent)r], %(child)r, m)',
-    )
-    "additional line(s) when a parent package is indicated"
-
-    @classmethod
-    def _gen_nspkg_line(cls, pkg):
-        # ensure pkg is not a unicode string under Python 2.7
-        pkg = str(pkg)
-        pth = tuple(pkg.split('.'))
-        tmpl_lines = cls._nspkg_tmpl
-        parent, sep, child = pkg.rpartition('.')
-        if parent:
-            tmpl_lines += cls._nspkg_tmpl_multi
-        return ';'.join(tmpl_lines) % locals() + '\n'
-
-    def _get_all_ns_packages(self):
-        """Return sorted list of all package namespaces"""
-        nsp = set()
-        for pkg in self.distribution.namespace_packages or []:
-            pkg = pkg.split('.')
-            while pkg:
-                nsp.add('.'.join(pkg))
-                pkg.pop()
-        return sorted(nsp)

setuptools/namespaces.py

@@ -0,0 +1,93 @@
+import os
+from distutils import log
+import itertools
+
+from setuptools.extern.six.moves import map
+
+
+flatten = itertools.chain.from_iterable
+
+
+class Installer:
+
+    nspkg_ext = '-nspkg.pth'
+
+    def install_namespaces(self):
+        nsp = self._get_all_ns_packages()
+        if not nsp:
+            return
+        filename, ext = os.path.splitext(self._get_target())
+        filename += self.nspkg_ext
+        self.outputs.append(filename)
+        log.info("Installing %s", filename)
+        lines = map(self._gen_nspkg_line, nsp)
+
+        if self.dry_run:
+            # always generate the lines, even in dry run
+            list(lines)
+            return
+
+        with open(filename, 'wt') as f:
+            f.writelines(lines)
+
+    def _get_target(self):
+        return self.target
+
+    _nspkg_tmpl = (
+        "import sys, types, os",
+        "pep420 = sys.version_info > (3, 3)",
+        "p = os.path.join(%(root)s, *%(pth)r)",
+        "ie = os.path.exists(os.path.join(p,'__init__.py'))",
+        "m = not ie and not pep420 and "
+            "sys.modules.setdefault(%(pkg)r, types.ModuleType(%(pkg)r))",
+        "mp = (m or []) and m.__dict__.setdefault('__path__',[])",
+        "(p not in mp) and mp.append(p)",
+    )
+    "lines for the namespace installer"
+
+    _nspkg_tmpl_multi = (
+        'm and setattr(sys.modules[%(parent)r], %(child)r, m)',
+    )
+    "additional line(s) when a parent package is indicated"
+
+    def _get_root(self):
+        return "sys._getframe(1).f_locals['sitedir']"
+
+    def _gen_nspkg_line(self, pkg):
+        # ensure pkg is not a unicode string under Python 2.7
+        pkg = str(pkg)
+        pth = tuple(pkg.split('.'))
+        root = self._get_root()
+        tmpl_lines = self._nspkg_tmpl
+        parent, sep, child = pkg.rpartition('.')
+        if parent:
+            tmpl_lines += self._nspkg_tmpl_multi
+        return ';'.join(tmpl_lines) % locals() + '\n'
+
+    def _get_all_ns_packages(self):
+        """Return sorted list of all package namespaces"""
+        pkgs = self.distribution.namespace_packages or []
+        return sorted(flatten(map(self._pkg_names, pkgs)))
+
+    @staticmethod
+    def _pkg_names(pkg):
+        """
+        Given a namespace package, yield the components of that
+        package.
+
+        >>> names = Installer._pkg_names('a.b.c')
+        >>> set(names) == set(['a', 'a.b', 'a.b.c'])
+        True
+        """
+        parts = pkg.split('.')
+        while parts:
+            yield '.'.join(parts)
+            parts.pop()
+
+
+class DevelopInstaller(Installer):
+    def _get_root(self):
+        return repr(str(self.egg_path))
+
+    def _get_target(self):
+        return self.egg_link