Rework setup to allow installing on Python 2 and 3.

Scripts named ipython and ipython[23], etc.

Neither distutils nor setuptools made this easy.

setup.py

@@ -58,8 +58,8 b' from setupbase import ('
     setup_args,
     find_packages,
     find_package_data,
-    find_scripts,
-    build_scripts_rename,
+    find_entry_points,
+    build_scripts_entrypt,
     find_data_files,
     check_for_dependencies,
     git_prebuild,
@@ -68,6 +68,9 b' from setupbase import ('
     require_submodules,
     UpdateSubmodules,
     CompileCSS,
+    install_symlinked,
+    install_lib_symlink,
+    install_scripts_for_symlink,
 )
 from setupext import setupext
 
@@ -148,7 +151,6 b' require_clean_submodules()'
 
 # update the manuals when building a source dist
 if len(sys.argv) >= 2 and sys.argv[1] in ('sdist','bdist_rpm'):
-    import textwrap
 
     # List of things to be updated. Each entry is a triplet of args for
     # target_update()
@@ -231,6 +233,9 b" setup_args['cmdclass'] = {"
     'upload_wininst' : UploadWindowsInstallers,
     'submodule' : UpdateSubmodules,
     'css' : CompileCSS,
+    'symlink': install_symlinked,
+    'install_lib_symlink': install_lib_symlink,
+    'install_scripts_sym': install_scripts_for_symlink,
 }
 
 #---------------------------------------------------------------------------
@@ -263,7 +268,7 b" if 'setuptools' in sys.modules:"
     setup_args['cmdclass']['develop'] = require_submodules(develop)
     
     setuptools_extra_args['zip_safe'] = False
-    setuptools_extra_args['entry_points'] = find_scripts(True, suffix = '3' if PY3 else '')
+    setuptools_extra_args['entry_points'] = {'console_scripts':find_entry_points()}
     setup_args['extras_require'] = dict(
         parallel = 'pyzmq>=2.1.11',
         qtconsole = ['pyzmq>=2.1.11', 'pygments'],
@@ -316,10 +321,10 b' else:'
     # check for dependencies an inform the user what is needed.  This is
     # just to make life easy for users.
     check_for_dependencies()
-    setup_args['scripts'] = find_scripts(False)
-    if PY3:
-        # Rename scripts with '3' suffix
-        setup_args['cmdclass']['build_scripts'] = build_scripts_rename
+    # scripts has to be a non-empty list, or install_scripts isn't called
+    setup_args['scripts'] = [e.split('=')[0].strip() for e in find_entry_points()]
+
+    setup_args['cmdclass']['build_scripts'] = build_scripts_entrypt
 
 #---------------------------------------------------------------------------
 # Do the actual setup now

setupbase.py

@@ -20,15 +20,14 b' from __future__ import print_function'
 #-------------------------------------------------------------------------------
 # Imports
 #-------------------------------------------------------------------------------
+import errno
 import os
 import sys
 
-try:
-    from configparser import ConfigParser
-except:
-    from ConfigParser import ConfigParser
 from distutils.command.build_py import build_py
 from distutils.command.build_scripts import build_scripts
+from distutils.command.install import install
+from distutils.command.install_scripts import install_scripts
 from distutils.cmd import Command
 from glob import glob
 from subprocess import call
@@ -311,7 +310,7 b' def target_update(target,deps,cmd):'
 # Find scripts
 #---------------------------------------------------------------------------
 
-def find_scripts(entry_points=False, suffix=''):
+def find_entry_points():
     """Find IPython's scripts.
 
     if entry_points is True:
@@ -322,8 +321,7 b" def find_scripts(entry_points=False, suffix=''):"
     suffix is appended to script names if entry_points is True, so that the
     Python 3 scripts get named "ipython3" etc.
     """
-    if entry_points:
-        console_scripts = [s % suffix for s in [
+    ep = [
             'ipython%s = IPython:start_ipython',
             'ipcontroller%s = IPython.parallel.apps.ipcontrollerapp:launch_new_instance',
             'ipengine%s = IPython.parallel.apps.ipengineapp:launch_new_instance',
@@ -331,37 +329,85 b" def find_scripts(entry_points=False, suffix=''):"
             'ipcluster%s = IPython.parallel.apps.ipclusterapp:launch_new_instance',
             'iptest%s = IPython.testing.iptestcontroller:main',
             'irunner%s = IPython.lib.irunner:main',
-        ]]
-        gui_scripts = []
-        scripts = dict(console_scripts=console_scripts, gui_scripts=gui_scripts)
-    else:
-        parallel_scripts = pjoin('IPython','parallel','scripts')
-        main_scripts = pjoin('IPython','scripts')
-        scripts = [
-                   pjoin(parallel_scripts, 'ipengine'),
-                   pjoin(parallel_scripts, 'ipcontroller'),
-                   pjoin(parallel_scripts, 'ipcluster'),
-                   pjoin(parallel_scripts, 'iplogger'),
-                   pjoin(main_scripts, 'ipython'),
-                   pjoin(main_scripts, 'irunner'),
-                   pjoin(main_scripts, 'iptest')
         ]
-    return scripts
+    suffix = str(sys.version_info[0])
+    return [e % '' for e in ep] + [e % suffix for e in ep]
+
+script_src = """#!{executable}
+from {mod} import {func}
+{func}()
+"""
+
+class build_scripts_entrypt(build_scripts):
+    def run(self):
+        self.mkpath(self.build_dir)
+        outfiles = []
+        for script in find_entry_points():
+            name, entrypt = script.split('=')
+            name = name.strip()
+            entrypt = entrypt.strip()
+            outfile = os.path.join(self.build_dir, name)
+            outfiles.append(outfile)
+            print('Writing script to', outfile)
+
+            mod, func = entrypt.split(':')
+            with open(outfile, 'w') as f:
+                f.write(script_src.format(executable=sys.executable,
+                                          mod=mod, func=func))
+
+        return outfiles, outfiles
+
+class install_lib_symlink(Command):
+    user_options = [
+        ('install-dir=', 'd', "directory to install to"),
+        ]
+
+    def initialize_options(self):
+        self.install_dir = None
 
-class build_scripts_rename(build_scripts):
-    """Use this on Python 3 to rename scripts to ipython3 etc."""
-    _suffix = '3'
+    def finalize_options(self):
+        self.set_undefined_options('symlink',
+                                   ('install_lib', 'install_dir'),
+                                  )
+
+    def run(self):
+        if sys.platform == 'win32':
+            raise Exception("This doesn't work on Windows.")
+        pkg = os.path.join(os.getcwd(), 'IPython')
+        dest = os.path.join(self.install_dir, 'IPython')
+        print('symlinking %s -> %s' % (pkg, dest))
+        try:
+            os.symlink(pkg, dest)
+        except OSError as e:
+            if e.errno == errno.EEXIST:
+                print('ALREADY EXISTS')
+            else:
+                raise
+
+class install_symlinked(install):
+    def run(self):
+        if sys.platform == 'win32':
+            raise Exception("This doesn't work on Windows.")
+        install.run(self)
     
-    def copy_scripts(self):
-        outfiles, updated_files = super(build_scripts_rename, self).copy_scripts()
-        new_outfiles = [p + self._suffix for p in outfiles]
-        updated_files = [p + self._suffix for p in updated_files]
-        for old, new in zip(outfiles, new_outfiles):
-            if os.path.exists(new):
-                os.unlink(new) 
-            self.move_file(old, new)
-        return new_outfiles, updated_files
-            
+    # 'sub_commands': a list of commands this command might have to run to
+    # get its work done.  See cmd.py for more info.
+    sub_commands = [('install_lib_symlink', lambda self:True),
+                    ('install_scripts_sym', lambda self:True),
+                   ]
+
+class install_scripts_for_symlink(install_scripts):
+    """Redefined to get options from 'symlink' instead of 'install'.
+    
+    I love distutils almost as much as I love setuptools.
+    """
+    def finalize_options(self):
+        self.set_undefined_options('build', ('build_scripts', 'build_dir'))
+        self.set_undefined_options('symlink',
+                                   ('install_scripts', 'install_dir'),
+                                   ('force', 'force'),
+                                   ('skip_build', 'skip_build'),
+                                  )
 
 #---------------------------------------------------------------------------
 # Verify all dependencies