New, cleaner package repository structure.

Package repositories now look like this:

    top-level-dir/
        repo.yaml
        packages/
            libelf/
                package.py
            mpich/
                package.py
            ...

This leaves room at the top level for additional metadata, source,
per-repo configs, indexes, etc., and it makes it easy to see that
something is a spack repo (just look for repo.yaml and packages).

var/spack/repos/builtin/packages/python/package.py

@@ -0,0 +1,160 @@
+import os
+import re
+from contextlib import closing
+from llnl.util.lang import match_predicate
+
+from spack import *
+import spack
+
+
+class Python(Package):
+    """The Python programming language."""
+    homepage = "http://www.python.org"
+    url      = "http://www.python.org/ftp/python/2.7.8/Python-2.7.8.tar.xz"
+
+    extendable = True
+
+    version('2.7.8', 'd235bdfa75b8396942e360a70487ee00')
+    version('2.7.10', 'c685ef0b8e9f27b5e3db5db12b268ac6')
+
+    depends_on("openssl")
+    depends_on("bzip2")
+    depends_on("readline")
+    depends_on("ncurses")
+    depends_on("sqlite")
+
+    def install(self, spec, prefix):
+        # Need this to allow python build to find the Python installation.
+        env['PYTHONHOME'] = prefix
+
+        # Rest of install is pretty standard.
+        configure("--prefix=%s" % prefix,
+                  "--with-threads",
+                  "--enable-shared")
+        make()
+        make("install")
+
+
+    # ========================================================================
+    # Set up environment to make install easy for python extensions.
+    # ========================================================================
+
+    @property
+    def python_lib_dir(self):
+        return os.path.join('lib', 'python%d.%d' % self.version[:2])
+
+
+    @property
+    def python_include_dir(self):
+        return os.path.join('include', 'python%d.%d' % self.version[:2])
+
+
+    @property
+    def site_packages_dir(self):
+        return os.path.join(self.python_lib_dir, 'site-packages')
+
+
+    def setup_dependent_environment(self, module, spec, ext_spec):
+        """Called before python modules' install() methods.
+
+        In most cases, extensions will only need to have one line::
+
+            python('setup.py', 'install', '--prefix=%s' % prefix)
+        """
+        # Python extension builds can have a global python executable function
+        module.python = Executable(join_path(spec.prefix.bin, 'python'))
+
+        # Add variables for lib/pythonX.Y and lib/pythonX.Y/site-packages dirs.
+        module.python_lib_dir     = os.path.join(ext_spec.prefix, self.python_lib_dir)
+        module.python_include_dir = os.path.join(ext_spec.prefix, self.python_include_dir)
+        module.site_packages_dir  = os.path.join(ext_spec.prefix, self.site_packages_dir)
+
+        # Make the site packages directory if it does not exist already.
+        mkdirp(module.site_packages_dir)
+
+        # Set PYTHONPATH to include site-packages dir for the
+        # extension and any other python extensions it depends on.
+        python_paths = []
+        for d in ext_spec.traverse():
+            if d.package.extends(self.spec):
+                python_paths.append(os.path.join(d.prefix, self.site_packages_dir))
+        os.environ['PYTHONPATH'] = ':'.join(python_paths)
+
+
+    # ========================================================================
+    # Handle specifics of activating and deactivating python modules.
+    # ========================================================================
+
+    def python_ignore(self, ext_pkg, args):
+        """Add some ignore files to activate/deactivate args."""
+        ignore_arg = args.get('ignore', lambda f: False)
+
+        # Always ignore easy-install.pth, as it needs to be merged.
+        patterns = [r'easy-install\.pth$']
+
+        # Ignore pieces of setuptools installed by other packages.
+        if ext_pkg.name != 'py-setuptools':
+            patterns.append(r'/site\.pyc?$')
+            patterns.append(r'setuptools\.pth')
+            patterns.append(r'bin/easy_install[^/]*$')
+            patterns.append(r'setuptools.*egg$')
+
+        return match_predicate(ignore_arg, patterns)
+
+
+    def write_easy_install_pth(self, exts):
+        paths = []
+        for ext in sorted(exts.values()):
+            ext_site_packages = os.path.join(ext.prefix, self.site_packages_dir)
+            easy_pth = "%s/easy-install.pth" % ext_site_packages
+
+            if not os.path.isfile(easy_pth):
+                continue
+
+            with closing(open(easy_pth)) as f:
+                for line in f:
+                    line = line.rstrip()
+
+                    # Skip lines matching these criteria
+                    if not line: continue
+                    if re.search(r'^(import|#)', line): continue
+                    if (ext.name != 'py-setuptools' and
+                        re.search(r'setuptools.*egg$', line)): continue
+
+                    paths.append(line)
+
+        site_packages = os.path.join(self.prefix, self.site_packages_dir)
+        main_pth = "%s/easy-install.pth" % site_packages
+
+        if not paths:
+            if os.path.isfile(main_pth):
+                os.remove(main_pth)
+
+        else:
+            with closing(open(main_pth, 'w')) as f:
+                f.write("import sys; sys.__plen = len(sys.path)\n")
+                for path in paths:
+                    f.write("%s\n" % path)
+                f.write("import sys; new=sys.path[sys.__plen:]; del sys.path[sys.__plen:]; "
+                        "p=getattr(sys,'__egginsert',0); sys.path[p:p]=new; sys.__egginsert = p+len(new)\n")
+
+
+    def activate(self, ext_pkg, **args):
+        ignore=self.python_ignore(ext_pkg, args)
+        args.update(ignore=ignore)
+
+        super(Python, self).activate(ext_pkg, **args)
+
+        exts = spack.install_layout.extension_map(self.spec)
+        exts[ext_pkg.name] = ext_pkg.spec
+        self.write_easy_install_pth(exts)
+
+
+    def deactivate(self, ext_pkg, **args):
+        args.update(ignore=self.python_ignore(ext_pkg, args))
+        super(Python, self).deactivate(ext_pkg, **args)
+
+        exts = spack.install_layout.extension_map(self.spec)
+        if ext_pkg.name in exts:        # Make deactivate idempotent.
+            del exts[ext_pkg.name]
+            self.write_easy_install_pth(exts)