Unfinished, untested implementation of the lovely baroque installation scheme
cooked up by Fred Drake and me.  Only saved for posterity (whoever posterity
is), as it is about to be ditched in favour of GvR's much simpler design.
diff --git a/Lib/distutils/command/install.py b/Lib/distutils/command/install.py
index ffd6879..a89bc02 100644
--- a/Lib/distutils/command/install.py
+++ b/Lib/distutils/command/install.py
@@ -10,7 +10,7 @@
 from types import *
 from distutils.core import Command
 from distutils.util import write_file
-
+from distutils.errors import DistutilsOptionError
 
 class install (Command):
 
@@ -21,7 +21,15 @@
         ('exec-prefix=', None,
          "prefix for platform-specific files"),
 
-        # Build directories: where to install from
+        # Installation directories: where to put modules and packages
+        ('install-lib=', None,
+         "base Python library directory"),
+        ('install-platlib=', None,
+         "platform-specific Python library directory"),
+        ('install-path=', None,
+         "extra intervening directories to put below install-lib"),
+
+        # Build directories: where to find the files to install
         ('build-base=', None,
          "base build directory"),
         ('build-lib=', None,
@@ -29,58 +37,36 @@
         ('build-platlib=', None,
          "build directory for extension modules"),
 
-        # Installation directories: where to put modules and packages
-        ('install-lib=', None,
-         "base Python library directory"),
-        ('install-platlib=', None,
-         "platform-specific Python library directory"),
-        ('install-site-lib=', None,
-         "directory for site-specific packages and modules"),
-        ('install-site-platlib=', None,
-         "platform-specific site directory"),
-        ('install-scheme=', None,
-         "install to 'system' or 'site' library directory?"),
-        ('install-path=', None,
-         "extra intervening directories to put below install-lib"),
-
         # Where to install documentation (eventually!)
-        ('doc-format=', None, "format of documentation to generate"),
-        ('install-man=', None, "directory for Unix man pages"),
-        ('install-html=', None, "directory for HTML documentation"),
-        ('install-info=', None, "directory for GNU info files"),
+        #('doc-format=', None, "format of documentation to generate"),
+        #('install-man=', None, "directory for Unix man pages"),
+        #('install-html=', None, "directory for HTML documentation"),
+        #('install-info=', None, "directory for GNU info files"),
 
         # Flags for 'build_py'
-        ('compile-py', None, "compile .py to .pyc"),
-        ('optimize-py', None, "compile .py to .pyo (optimized)"),
+        #('compile-py', None, "compile .py to .pyc"),
+        #('optimize-py', None, "compile .py to .pyo (optimized)"),
         ]
 
 
     def initialize_options (self):
 
-        self.build_base = None
-        self.build_lib = None
-        self.build_platlib = None
-
         # Don't define 'prefix' or 'exec_prefix' so we can know when the
         # command is run whether the user supplied values
         self.prefix = None
         self.exec_prefix = None
 
-        # These two, we can supply real values for! (because they're
-        # not directories, and don't have a confusing multitude of
-        # possible derivations)
-        #self.install_scheme = 'site'
-        self.doc_format = None
-
         # The actual installation directories are determined only at
         # run-time, so the user can supply just prefix (and exec_prefix?)
         # as a base for everything else
         self.install_lib = None
         self.install_platlib = None
-        self.install_site_lib = None
-        self.install_site_platlib = None
         self.install_path = None
 
+        self.build_base = None
+        self.build_lib = None
+        self.build_platlib = None
+
         self.install_man = None
         self.install_html = None
         self.install_info = None
@@ -114,75 +100,90 @@
         # and assumes the Python 1.5 installation tree with no site.py
         # to fix things.
 
-        # Figure out the build directories, ie. where to install from
-        self.set_peer_option ('build', 'build_base', self.build_base)
-        self.set_undefined_options ('build',
-                                    ('build_base', 'build_base'),
-                                    ('build_lib', 'build_lib'),
-                                    ('build_platlib', 'build_platlib'))
-
         # Figure out actual installation directories; the basic principle
-        # is: if the user supplied nothing, then use the directories that
-        # Python was built and installed with (ie. the compiled-in prefix
-        # and exec_prefix, and the actual installation directories gleaned
-        # by sysconfig).  If the user supplied a prefix (and possibly
-        # exec_prefix), then we generate our own installation directories,
-        # following any pattern gleaned from sysconfig's findings.  If no
-        # such pattern can be gleaned, then we'll just make do and try to
-        # ape the behaviour of Python's configure script.
+        # is: ...
 
-        if self.prefix is None:         # user didn't override
-            self.prefix = os.path.normpath (sys.prefix)
-        if self.exec_prefix is None:
-            self.exec_prefix = os.path.normpath (sys.exec_prefix)
+        sys_prefix = os.path.normpath (sys.prefix)
+        sys_exec_prefix = os.path.normpath (sys.exec_prefix)
 
-        if self.install_lib is None:
-            self.install_lib = \
-                self.replace_sys_prefix ('LIBDEST', ('lib','python1.5'))
-        if self.install_platlib is None:
-            # XXX this should probably be DESTSHARED -- but why is there no
-            # equivalent to DESTSHARED for the "site-packages" dir"?
-            self.install_platlib = \
-                self.replace_sys_prefix ('BINLIBDEST', ('lib','python1.5'), 1)
-
-
-        # Here is where we decide where to install most library files: on
-        # POSIX systems, they go to 'site-packages' under the install_lib
-        # (determined above -- typically /usr/local/lib/python1.x).  Note
-        # that on POSIX systems, platform-specific files belong in
-        # 'site-packages' under install_platlib.  (The actual rule is that
-        # a module distribution that includes *any* platform-specific files
-        # -- ie. extension modules -- goes under install_platlib.  This
-        # solves the "can't find extension module in a package" problem.)
-        # On non-POSIX systems, install_lib and install_platlib are the
-        # same (eg. "C:\Program Files\Python\Lib" on Windows), as are
-        # install_site_lib and install_site_platlib (eg.
-        # "C:\Program Files\Python" on Windows) -- everything will be dumped
-        # right into one of the install_site directories.  (It doesn't
-        # really matter *which* one, of course, but I'll observe decorum
-        # and do it properly.)
-
-        # 'base' and 'platbase' are the base directories for installing
-        # site-local files, eg. "/usr/local/lib/python1.5/site-packages"
-        # or "C:\Program Files\Python"
-        if os.name == 'posix':
-            self.base = os.path.join (self.install_lib,
-                                      'site-packages')
-            self.platbase = os.path.join (self.install_platlib,
-                                          'site-packages')
+        if self.prefix is None:
+            if self.exec_prefix is not None:
+                raise DistutilsOptionError, \
+                      "you may not supply exec_prefix without prefix"
+            self.prefix = sys_prefix
         else:
-            self.base = self.prefix
-            self.platbase = self.exec_prefix
-        
-        # 'path_file' and 'extra_dirs' are how we handle distributions
-        # that need to be installed to their own directory, but aren't
+            # This is handy to guarantee that self.prefix is normalized --
+            # but it could be construed as rude to go normalizing a
+            # user-supplied path (they might like to see their "../" or
+            # symlinks in the installation feedback).
+            self.prefix = os.path.normpath (self.prefix)
+            
+        if self.exec_prefix is None:
+            if self.prefix == sys_prefix:
+                self.exec_prefix = sys_exec_prefix
+            else:
+                self.exec_prefix = self.prefix
+        else:
+            # Same as above about handy versus rude to normalize user's
+            # exec_prefix.
+            self.exec_prefix = os.path.normpath (self.exec_prefix)
+
+        if self.distribution.ext_modules: # any extensions to install?
+            effective_prefix = self.exec_prefix
+        else:
+            effective_prefix = self.prefix
+
+        if os.name == 'posix':
+            if self.install_lib is None:
+                if self.prefix == sys_prefix:
+                    self.install_lib = \
+                        os.path.join (effective_prefix,
+                                      "lib",
+                                      "python" + sys.version[:3],
+                                      "site-packages")
+                else:
+                    self.install_lib = \
+                        os.path.join (effective_prefix,
+                                      "lib",
+                                      "python")      # + sys.version[:3] ???
+            # end if self.install_lib ...
+
+            if self.install_platlib is None:
+                if self.exec_prefix == sys_exec_prefix:
+                    self.install_platlib = \
+                        os.path.join (effective_prefix,
+                                      "lib",
+                                      "python" + sys.version[:3],
+                                      "site-packages")
+                else:
+                    self.install_platlib = \
+                        os.path.join (effective_prefix,
+                                      "lib",
+                                      "python")      # + sys.version[:3] ???
+            # end if self.install_platlib ...
+
+        else:
+            raise DistutilsPlatformError, \
+                  "duh, I'm clueless (for now) about installing on %s" % os.name
+
+        # end if/else on os.name
+                    
+
+        # 'path_file' and 'extra_dirs' are how we handle distributions that
+        # want to be installed to their own directory, but aren't
         # package-ized yet.  'extra_dirs' is just a directory under
-        # 'base' or 'platbase' where toplevel modules will actually be
-        # installed; 'path_file' is the basename of a .pth file to drop
-        # in 'base' or 'platbase' (depending on the distribution).  Very
-        # often they will be the same, which is why we allow them to be
-        # supplied as a string or 1-tuple as well as a 2-element
-        # comma-separated string or a 2-tuple.
+        # 'install_lib' or 'install_platlib' where top-level modules will
+        # actually be installed; 'path_file' is the basename of a .pth file
+        # to drop in 'install_lib' or 'install_platlib' (depending on the
+        # distribution).  Very often they will be the same, which is why we
+        # allow them to be supplied as a string or 1-tuple as well as a
+        # 2-element comma-separated string or a 2-tuple.
+
+        # XXX this will drop a .pth file in install_{lib,platlib} even if
+        # they're not one of the site-packages directories: this is wrong!
+        # we need to suppress path_file in those cases, and warn if
+        # "install_lib/extra_dirs" is not in sys.path.
+
         if self.install_path is None:
             self.install_path = self.distribution.install_path
 
@@ -214,25 +215,12 @@
         self.extra_dirs = extra_dirs
 
 
-        if self.install_site_lib is None:
-            self.install_site_lib = os.path.join (self.base,
-                                                  extra_dirs)
-
-        if self.install_site_platlib is None:
-            self.install_site_platlib = os.path.join (self.platbase,
-                                                      extra_dirs)
-
-        #if self.install_scheme == 'site':
-        #    install_lib = self.install_site_lib
-        #    install_platlib = self.install_site_platlib
-        #elif self.install_scheme == 'system':
-        #    install_lib = self.install_lib
-        #    install_platlib = self.install_platlib
-        #else:
-        #    # XXX new exception for this kind of misbehaviour?
-        #    raise DistutilsArgError, \
-        #          "invalid install scheme '%s'" % self.install_scheme
-            
+        # Figure out the build directories, ie. where to install from
+        self.set_peer_option ('build', 'build_base', self.build_base)
+        self.set_undefined_options ('build',
+                                    ('build_base', 'build_base'),
+                                    ('build_lib', 'build_lib'),
+                                    ('build_platlib', 'build_platlib'))
 
         # Punt on doc directories for now -- after all, we're punting on
         # documentation completely!
@@ -240,50 +228,13 @@
     # finalize_options ()
 
 
-    def replace_sys_prefix (self, config_attr, fallback_postfix, use_exec=0):
-        """Attempts to glean a simple pattern from an installation
-           directory available as a 'sysconfig' attribute: if the
-           directory name starts with the "system prefix" (the one
-           hard-coded in the Makefile and compiled into Python),
-           then replace it with the current installation prefix and
-           return the "relocated" installation directory."""
-
-        from distutils import sysconfig
-
-        if use_exec:
-            sys_prefix = os.path.normpath (sys.exec_prefix)
-            my_prefix = self.exec_prefix
-        else:
-            sys_prefix = os.path.normpath (sys.prefix)
-            my_prefix = self.prefix
-
-        val = getattr (sysconfig, config_attr)
-        if string.find (val, sys_prefix) == 0:
-            # If the sysconfig directory starts with the system prefix,
-            # then we can "relocate" it to the user-supplied prefix --
-            # assuming, of course, it is different from the system prefix.
-
-            if sys_prefix == my_prefix:
-                return val
-            else:
-                return my_prefix + val[len(sys_prefix):]
-
-        else:
-            # Otherwise, just tack the "fallback postfix" onto the
-            # user-specified prefix.
-
-            return apply (os.path.join, (my_prefix,) + fallback_postfix)
-
-    # replace_sys_prefix ()
-    
-
     def run (self):
 
         # Obviously have to build before we can install
         self.run_peer ('build')
 
         # Install modules in two steps: "platform-shared" files (ie. pure
-        # python modules) and platform-specific files (compiled C
+        # Python modules) and platform-specific files (compiled C
         # extensions).  Note that 'install_py' is smart enough to install
         # pure Python modules in the "platlib" directory if we built any
         # extensions.