Ditch the special treatment of None

8 files changed, 136 insertions, 107 deletions

diff --git a/attoconf/_version.py b/attoconf/_version.py
index 28024a6..18e1fb6 100644
--- a/attoconf/_version.py
+++ b/attoconf/_version.py
@@ -7,11 +7,11 @@ major = 0
 
 # Incremented for releases with compatible API additions.
 # This is the number that is usually incremented.
-minor = 8
+minor = 9
 
 # Incremented if there is a bugfix release.
 # Might not be contiguous.
-patch = 6
+patch = 0
 
 # Reserved for distributors and forks.
 # Contains arbitrary text, but no parentheses or newlines.
diff --git a/attoconf/classy.py b/attoconf/classy.py
index a2891dc..a27230d 100644
--- a/attoconf/classy.py
+++ b/attoconf/classy.py
@@ -68,9 +68,9 @@ class ClassyProject(Project):
         self.add_help('General:', hidden=False)
         self.add_alias('--help', ['--help=default'],
                 help='display standard help, then exit', hidden=False)
-        self.add_option('--help', init=None,
+        self.add_option('--help', init='none',
                 type=self.do_help, check=None,
-                help='display some kind of help', hidden=False,
+                help='just display some kind of help instead of configuring', hidden=False,
                 help_var='KIND')
         self.help.add_option('--help=hidden',
                 help='display help you should never ever ever care about',
diff --git a/attoconf/core.py b/attoconf/core.py
index bb9d2ba..0d196e9 100644
--- a/attoconf/core.py
+++ b/attoconf/core.py
@@ -103,8 +103,9 @@ class Project(object):
             # used by some tests ... should this be fixed there instead?
             if help_var is None:
                 help_var = var
-        if init is not None:
-            init = type(init)
+        assert init is not None
+        init = type(init)
+        assert init is not None
         self.options[name] = Option(init=init, type=type)
         if check is not None:
             self.order.append(var)
@@ -113,10 +114,11 @@ class Project(object):
 
         if help_var is None:
             help_var = var
+
         if help_def is None:
             help_def = init
-        if help_def is not None:
-            help = '%s [%s]' % (help, help_def)
+        assert help_def is not None
+        help = '%s [%s]' % (help, help_def)
 
         if help_var != name:
             help_opt = '%s=%s' % (name, help_var)
@@ -127,12 +129,14 @@ class Project(object):
     def do_help(self, opt):
         ''' Pseudo type-hook to be registered for --help (calls sys.exit).
         '''
+        if opt == 'none':
+            return opt
         if opt == 'default':
             hidden = False
         elif opt == 'hidden':
             hidden = True
         else:
-            raise ValueError
+            raise ValueError('Unknown value for opt: %r' % opt)
         self.help.print(sys.stdout, hidden)
         sys.exit()
 # sneaky
diff --git a/attoconf/lib/arches.py b/attoconf/lib/arches.py
index cffd8ca..8c70f0b 100644
--- a/attoconf/lib/arches.py
+++ b/attoconf/lib/arches.py
@@ -18,21 +18,19 @@
 from __future__ import print_function, division, absolute_import
 
 from ..classy import ClassyProject
-from ..types import triple
+from ..types import triple, maybe
 
 
-# TODO: see if there's a way to expose them sanely, without using Nones
-# (currently I never emit them: instead I pop the order)
 def build(build, BUILD):
     pass
 
 def host(build, HOST):
-    if HOST is None:
+    if not HOST:
         BUILD = build.vars['BUILD']
         build.vars['HOST'] = BUILD
 
 def target(build, TARGET):
-    if TARGET is None:
+    if not TARGET:
         HOST = build.vars['HOST']
         build.vars['TARGET'] = HOST
 
@@ -42,24 +40,21 @@ class Arches2(ClassyProject):
     def arches(self):
         super(Arches2, self).arches()
         self.add_help('System types:', hidden=False)
-        self.add_option('--build', init=None,
-                type=triple, check=build,
+        self.add_option('--build', init='',
+                type=maybe(triple), check=build,
                 help='configure for building on BUILD', hidden=False,
                 help_def='native')
-        self.order.pop()
-        self.add_option('--host', init=None,
-                type=triple, check=host,
+        self.add_option('--host', init='',
+                type=maybe(triple), check=host,
                 help='cross-compile to build programs to run on HOST',
                 hidden=False, help_def='BUILD')
-        self.order.pop()
 
 # TODO figure out the mro implications when I use this
 class Arches3(Arches2):
     __slots__ = ()
     def arches(self):
         super(Arches3, self).arches()
-        self.add_option('--target', init=None,
-                type=triple, check=target,
+        self.add_option('--target', init='',
+                type=maybe(triple), check=target,
                 help='configure for building compilers for TARGET',
                 hidden=False, help_def='HOST')
-        self.order.pop()
diff --git a/attoconf/lib/c.py b/attoconf/lib/c.py
index 3b6f05f..bc32c49 100644
--- a/attoconf/lib/c.py
+++ b/attoconf/lib/c.py
@@ -208,7 +208,12 @@ def cppflags(build, CPPFLAGS):
     pass
 
 def cc(build, CC):
-    pass
+    if CC.list == []:
+        HOST = build.vars['HOST']
+        if HOST:
+            build.vars['CC'].list = [HOST + '-gcc']
+        else:
+            build.vars['CC'].list = ['gcc']
 
 def cflags(build, CFLAGS):
     try_compile_c(build, 'int main() {}\n')
@@ -216,7 +221,12 @@ def cflags(build, CFLAGS):
     try_compile_link2_c(build, 'int main() {}\n')
 
 def cxx(build, CXX):
-    pass
+    if CXX.list == []:
+        HOST = build.vars['HOST']
+        if HOST:
+            build.vars['CXX'].list = [HOST + '-g++']
+        else:
+            build.vars['CXX'].list = ['g++']
 
 def cxxflags(build, CXXFLAGS):
     try_compile_cxx(build, 'int main() {}\n')
@@ -235,7 +245,7 @@ class Link(Arches2):
                 type=ShellList, check=libs,
                 help='libraries to pass to the linker, e.g. -l<library>',
                 hidden=False)
-        self.order.append('LDLIBS')
+        self.order.append('LDLIBS') #TODO remove for 1.0
 
 class Preprocess(Arches2):
     __slots__ = ()
@@ -250,9 +260,10 @@ class C(Link, Preprocess):
     __slots__ = ()
     def vars(self):
         super(C, self).vars()
-        self.add_option('CC', init=['gcc'],
+        self.add_option('CC', init=[],
                 type=ShellList, check=cc,
-                help='C compiler command', hidden=False)
+                help='C compiler command', hidden=False,
+                help_def='HOST-gcc')
         self.add_option('CFLAGS', init=['-O2', '-g'],
                 type=ShellList, check=cflags,
                 help='C compiler flags', hidden=False)
@@ -261,9 +272,10 @@ class Cxx(Link, Preprocess):
     __slots__ = ()
     def vars(self):
         super(Cxx, self).vars()
-        self.add_option('CXX', init=['g++'],
+        self.add_option('CXX', init=[],
                 type=ShellList, check=cxx,
-                help='C++ compiler command', hidden=False)
+                help='C++ compiler command', hidden=False,
+                help_def='HOST-g++')
         self.add_option('CXXFLAGS', init=['-O2', '-g'],
                 type=ShellList, check=cxxflags,
                 help='C++ compiler flags', hidden=False)
diff --git a/attoconf/lib/install.py b/attoconf/lib/install.py
index 1a55c29..f43b2a1 100644
--- a/attoconf/lib/install.py
+++ b/attoconf/lib/install.py
@@ -20,7 +20,7 @@ from __future__ import print_function, division, absolute_import
 import os
 
 from ..classy import ClassyProject
-from ..types import shell_word, filepath, quoted_string
+from ..types import shell_word, filepath, quoted_string, maybe
 
 
 def package(build, PACKAGE):
@@ -33,48 +33,48 @@ def prefix(build, PREFIX):
     pass
 
 def exec_prefix(build, EPREFIX):
-    if EPREFIX is None:
+    if not EPREFIX:
         PREFIX = build.vars['PREFIX']
         build.vars['EXEC_PREFIX'] = PREFIX
     build.vars['EPREFIX'] = build.vars['EXEC_PREFIX']
 
 def bindir(build, DIR):
-    if DIR is None:
+    if not DIR:
         EPREFIX = build.vars['EPREFIX']
         build.vars['BINDIR'] = os.path.join(EPREFIX, 'bin')
 
 def sbindir(build, DIR):
-    if DIR is None:
+    if not DIR:
         EPREFIX = build.vars['EPREFIX']
         build.vars['SBINDIR'] = os.path.join(EPREFIX, 'sbin')
 
 def libexecdir(build, DIR):
-    if DIR is None:
+    if not DIR:
         EPREFIX = build.vars['EPREFIX']
         build.vars['LIBEXECDIR'] = os.path.join(EPREFIX, 'libexec')
 
 def sysconfdir(build, DIR):
-    if DIR is None:
+    if not DIR:
         PREFIX = build.vars['PREFIX']
         build.vars['SYSCONFDIR'] = os.path.join(PREFIX, 'etc')
 
 def sharedstatedir(build, DIR):
-    if DIR is None:
+    if not DIR:
         PREFIX = build.vars['PREFIX']
         build.vars['SHAREDSTATEDIR'] = os.path.join(PREFIX, 'com')
 
 def localstatedir(build, DIR):
-    if DIR is None:
+    if not DIR:
         PREFIX = build.vars['PREFIX']
         build.vars['LOCALSTATEDIR'] = os.path.join(PREFIX, 'var')
 
 def libdir(build, DIR):
-    if DIR is None:
+    if not DIR:
         EPREFIX = build.vars['EPREFIX']
         build.vars['LIBDIR'] = os.path.join(EPREFIX, 'lib')
 
 def includedir(build, DIR):
-    if DIR is None:
+    if not DIR:
         PREFIX = build.vars['PREFIX']
         build.vars['INCLUDEDIR'] = os.path.join(PREFIX, 'include')
 
@@ -82,59 +82,59 @@ def oldincludedir(build, DIR):
     pass
 
 def datarootdir(build, DIR):
-    if DIR is None:
+    if not DIR:
         PREFIX = build.vars['PREFIX']
         build.vars['DATAROOTDIR'] = os.path.join(PREFIX, 'share')
 
 def datadir(build, DIR):
-    if DIR is None:
+    if not DIR:
         DATAROOTDIR = build.vars['DATAROOTDIR']
         build.vars['DATADIR'] = DATAROOTDIR
 
 def packagedatadir(build, DIR):
-    if DIR is None:
+    if not DIR:
         DATADIR = build.vars['DATADIR']
         PACKAGE = build.vars['PACKAGE']
         build.vars['PACKAGEDATADIR'] = os.path.join(DATADIR, PACKAGE)
 
 def infodir(build, DIR):
-    if DIR is None:
+    if not DIR:
         DATAROOTDIR = build.vars['DATAROOTDIR']
         build.vars['INFODIR'] = os.path.join(DATAROOTDIR, 'info')
 
 def localedir(build, DIR):
-    if DIR is None:
+    if not DIR:
         DATAROOTDIR = build.vars['DATAROOTDIR']
         build.vars['LOCALEDIR'] = os.path.join(DATAROOTDIR, 'locale')
 
 def mandir(build, DIR):
-    if DIR is None:
+    if not DIR:
         DATAROOTDIR = build.vars['DATAROOTDIR']
         build.vars['MANDIR'] = os.path.join(DATAROOTDIR, 'man')
 
 def docdir(build, DIR):
-    if DIR is None:
+    if not DIR:
         DATAROOTDIR = build.vars['DATAROOTDIR']
         PACKAGE = build.vars['PACKAGE']
         build.vars['DOCDIR'] = os.path.join(DATAROOTDIR, 'doc', PACKAGE)
 
 def htmldir(build, DIR):
-    if DIR is None:
+    if not DIR:
         DOCDIR = build.vars['DOCDIR']
         build.vars['HTMLDIR'] = DOCDIR
 
 def dvidir(build, DIR):
-    if DIR is None:
+    if not DIR:
         DOCDIR = build.vars['DOCDIR']
         build.vars['DVIDIR'] = DOCDIR
 
 def pdfdir(build, DIR):
-    if DIR is None:
+    if not DIR:
         DOCDIR = build.vars['DOCDIR']
         build.vars['PDFDIR'] = DOCDIR
 
 def psdir(build, DIR):
-    if DIR is None:
+    if not DIR:
         DOCDIR = build.vars['DOCDIR']
         build.vars['PSDIR'] = DOCDIR
 
@@ -179,93 +179,93 @@ class Install(ClassyProject):
                 type=filepath, check=prefix,
                 help='install architecture-independent files in PREFIX',
                 hidden=False)
-        self.add_option('--exec-prefix', init=None,
-                type=filepath, check=exec_prefix,
+        self.add_option('--exec-prefix', init='',
+                type=maybe(filepath), check=exec_prefix,
                 help='install architecture-dependent files in EPREFIX',
                 hidden=False,
                 help_var='EPREFIX', help_def='PREFIX')
-        self.order.append('EPREFIX')
+        self.order.append('EPREFIX') # TODO remove for 1.0
         self.order.append(None)
 
         self.add_help('Fine tuning of the installation directories:',
                 hidden=False)
-        self.add_option('--bindir', init=None,
-                type=filepath, check=bindir,
+        self.add_option('--bindir', init='',
+                type=maybe(filepath), check=bindir,
                 help='user executables', hidden=False,
                 help_var='DIR', help_def='EPREFIX/bin')
-        self.add_option('--sbindir', init=None,
-                type=filepath, check=sbindir,
+        self.add_option('--sbindir', init='',
+                type=maybe(filepath), check=sbindir,
                 help='system admin executables', hidden=False,
                 help_var='DIR', help_def='EPREFIX/sbin')
-        self.add_option('--libexecdir', init=None,
-                type=filepath, check=libexecdir,
+        self.add_option('--libexecdir', init='',
+                type=maybe(filepath), check=libexecdir,
                 help='program executables', hidden=False,
                 help_var='DIR', help_def='EPREFIX/libexec')
-        self.add_option('--sysconfdir', init=None,
-                type=filepath, check=sysconfdir,
+        self.add_option('--sysconfdir', init='',
+                type=maybe(filepath), check=sysconfdir,
                 help='read-only single-machine data', hidden=False,
                 help_var='DIR', help_def='PREFIX/etc')
-        self.add_option('--sharedstatedir', init=None,
-                type=filepath, check=sharedstatedir,
+        self.add_option('--sharedstatedir', init='',
+                type=maybe(filepath), check=sharedstatedir,
                 help='modifiable architecture-independent data', hidden=False,
                 help_var='DIR', help_def='PREFIX/com')
-        self.add_option('--localstatedir', init=None,
-                type=filepath, check=localstatedir,
+        self.add_option('--localstatedir', init='',
+                type=maybe(filepath), check=localstatedir,
                 help='modifiable single-machine data', hidden=False,
                 help_var='DIR', help_def='PREFIX/var')
-        self.add_option('--libdir', init=None,
-                type=filepath, check=libdir,
+        self.add_option('--libdir', init='',
+                type=maybe(filepath), check=libdir,
                 help='object code libraries', hidden=False,
                 help_var='DIR', help_def='EPREFIX/lib')
-        self.add_option('--includedir', init=None,
-                type=filepath, check=includedir,
+        self.add_option('--includedir', init='',
+                type=maybe(filepath), check=includedir,
                 help='C header files', hidden=False,
                 help_var='DIR', help_def='PREFIX/include')
         self.add_option('--oldincludedir', init='/usr/include',
                 type=filepath, check=oldincludedir,
                 help='C header files for non-gcc', hidden=False,
                 help_var='DIR')
-        self.add_option('--datarootdir', init=None,
-                type=filepath, check=datarootdir,
+        self.add_option('--datarootdir', init='',
+                type=maybe(filepath), check=datarootdir,
                 help='read-only arch.-independent data root', hidden=False,
                 help_var='DIR', help_def='PREFIX/share')
-        self.add_option('--datadir', init=None,
-                type=filepath, check=datadir,
+        self.add_option('--datadir', init='',
+                type=maybe(filepath), check=datadir,
                 help='read-only architecture-independent data', hidden=False,
                 help_var='DIR', help_def='DATAROOTDIR')
-        self.add_option('--packagedatadir', init=None,
-                type=filepath, check=packagedatadir,
+        self.add_option('--packagedatadir', init='',
+                type=maybe(filepath), check=packagedatadir,
                 help='data specific to this package (please set datadir instead)', hidden=False,
                 help_var='DIR', help_def='DATADIR/PACKAGE')
-        self.add_option('--infodir', init=None,
-                type=filepath, check=infodir,
+        self.add_option('--infodir', init='',
+                type=maybe(filepath), check=infodir,
                 help='info documentation', hidden=False,
                 help_var='DIR', help_def='DATAROOTDIR/info')
-        self.add_option('--localedir', init=None,
-                type=filepath, check=localedir,
+        self.add_option('--localedir', init='',
+                type=maybe(filepath), check=localedir,
                 help='locale-dependent data', hidden=False,
                 help_var='DIR', help_def='DATAROOTDIR/locale')
-        self.add_option('--mandir', init=None,
-                type=filepath, check=mandir,
+        self.add_option('--mandir', init='',
+                type=maybe(filepath), check=mandir,
                 help='man documentation', hidden=False,
                 help_var='DIR', help_def='DATAROOTDIR/man')
-        self.add_option('--docdir', init=None,
-                type=filepath, check=docdir,
+        self.add_option('--docdir', init='',
+                type=maybe(filepath), check=docdir,
                 help='documentation root', hidden=False,
                 help_var='DIR', help_def='DATAROOTDIR/doc/PACKAGE')
-        self.add_option('--htmldir', init=None,
-                type=filepath, check=htmldir,
+        self.add_option('--htmldir', init='',
+                type=maybe(filepath), check=htmldir,
                 help='html documentation', hidden=False,
                 help_var='DIR', help_def='DOCDIR')
-        self.add_option('--dvidir', init=None,
-                type=filepath, check=dvidir,
+        self.add_option('--dvidir', init='',
+                type=maybe(filepath), check=dvidir,
                 help='dvi documentation', hidden=False,
                 help_var='DIR', help_def='DOCDIR')
-        self.add_option('--pdfdir', init=None,
-                type=filepath, check=pdfdir,
+        self.add_option('--pdfdir', init='',
+                type=maybe(filepath), check=pdfdir,
                 help='pdf documentation', hidden=False,
                 help_var='DIR', help_def='DOCDIR')
-        self.add_option('--psdir', init=None,
-                type=filepath, check=psdir,
+        self.add_option('--psdir', init='',
+                type=maybe(filepath), check=psdir,
                 help='ps documentation', hidden=False,
                 help_var='DIR', help_def='DOCDIR')
diff --git a/attoconf/tests/test_core.py b/attoconf/tests/test_core.py
index f60aab6..09c2c64 100644
--- a/attoconf/tests/test_core.py
+++ b/attoconf/tests/test_core.py
@@ -20,7 +20,7 @@ from __future__ import print_function, division, absolute_import
 import unittest
 
 from attoconf.core import Project, Build
-from attoconf.types import uint, shell_word, shell_partial_word
+from attoconf.types import uint, shell_word, shell_partial_word, maybe
 
 import os
 from cStringIO import StringIO
@@ -44,7 +44,7 @@ class TestProject(unittest.TestCase):
         proj.add_help('General:', False)
         proj.add_alias('--help', ['--help=default'],
                 help='display standard help, then exit', hidden=False)
-        proj.add_option('--help', init=None,
+        proj.add_option('--help', init='none',
                 type=proj.do_help, check=None,
                 help='display some subset of help', hidden=False,
                 help_var='TYPE')
@@ -54,8 +54,8 @@ class TestProject(unittest.TestCase):
         proj.add_option('--foo', init='asdf',
                 type=shell_word, check=None,
                 help='set frob target', hidden=False)
-        proj.add_option('--bar', init=None,
-                type=shell_word, check=None,
+        proj.add_option('--bar', init='',
+                type=maybe(shell_word), check=None,
                 help='set frob source', hidden=False,
                 help_def='FOO')
 
@@ -68,7 +68,7 @@ class TestProject(unittest.TestCase):
         self.assertEqual(out.getvalue(), '''
 General:
   --help       display standard help, then exit
-  --help=TYPE  display some subset of help
+  --help=TYPE  display some subset of help [none]
   --foo=FOO    set frob target [asdf]
   --bar=BAR    set frob source [FOO]
 
@@ -81,7 +81,7 @@ General:
         self.assertEqual(out.getvalue(), '''
 General:
   --help         display standard help, then exit
-  --help=TYPE    display some subset of help
+  --help=TYPE    display some subset of help [none]
   --help=hidden  display help you should never ever ever care about
   --foo=FOO      set frob target [asdf]
   --bar=BAR      set frob source [FOO]
@@ -101,22 +101,23 @@ General:
         def check_bar(bld, BAR):
             self.assertEqual(BAR, 1)
         def check_qux(bld, QUX):
-            self.assertEqual(QUX, None)
+            self.assertEqual(QUX, '')
         def check_var(bld, VAR):
             self.assertEqual(VAR, 'value')
 
         proj = Project('.')
         proj.add_alias('--alias', ['--foo=A', '--bar=1', '--foo=B'],
                 help=None, hidden=False)
-        proj.add_option('--foo', init=None,
+        proj.add_option('--foo', init='X',
                 type=shell_word, check=check_foo,
                 help='help for string foo', hidden=False)
         proj.add_option('--bar', init=0,
                 type=uint, check=check_bar,
                 help='help for int bar', hidden=False)
-        proj.add_option('--qux', init=None,
-                type=uint, check=check_qux,
-                help='help for int qux', hidden=False)
+        proj.add_option('--qux', init='',
+                type=maybe(uint), check=check_qux,
+                help='help for int qux', hidden=False,
+                help_def='auto')
         proj.add_option('VAR', init='',
                 type=shell_partial_word, check=check_var,
                 help='help for string VAR', hidden=False)
@@ -133,6 +134,6 @@ General:
                 {
                     'FOO': 'B',
                     'BAR': 1,
-                    'QUX': None,
+                    'QUX': '',
                     'VAR': 'value',
                 })
diff --git a/attoconf/types.py b/attoconf/types.py
index 3e73d86..e7c8465 100644
--- a/attoconf/types.py
+++ b/attoconf/types.py
@@ -51,6 +51,18 @@ class enum(object):
         raise ValueError('%r not in {%s}' % (s, ', '.join(self.args)))
 
 
+class maybe(object):
+    __slots__ = ('inferior')
+
+    def __init__(self, inferior):
+        self.inferior = inferior
+
+    def __call__(self, s):
+        if not s:
+            return s
+        return (self.inferior)(s)
+
+
 class ShellList(object):
     ''' An argument type representing a sequence of 0 or more arguments
     '''
@@ -96,9 +108,14 @@ def quoted_string(s):
 
 def filepath(s):
     s = trim_trailing_slashes(s)
-    # must be absolute *and* canonical
-    if s != os.path.abspath(s):
-        raise ValueError('Not an absolute, canonical pathname: %s' % s)
+    # must be absolute *and* canonical, except joinable
+    a = os.path.abspath(s)
+    if a == '/':
+        # filepaths often directly cat a subpath
+        # @me@/whatever is invalid if @me@ == /
+        a = '/.'
+    if s != a:
+        raise ValueError('Not an absolute, canonical (except joinable) pathname: %r != %r' % (s, a))
     return s