Added a script-generation option to generate relative paths for eggs

in scripts when both the script and the eggs have a common base directory.

src/zc/buildout/easy_install.py

@@ -893,7 +893,8 @@ def develop(setup, dest,
         if is_jython:
             assert subprocess.Popen([_safe_arg(executable)] + args).wait() == 0
         else:
-            assert os.spawnl(os.P_WAIT, executable, _safe_arg (executable), *args) == 0
+            assert os.spawnl(os.P_WAIT, executable, _safe_arg(executable),
+                             *args) == 0
 
         return _copyeggs(tmp3, dest, '.egg-link', undo)
 
@@ -911,11 +912,13 @@ def scripts(reqs, working_set, executable, dest,
             arguments='',
             interpreter=None,
             initialization='',
+            relative_paths=False,
             ):
 
     path = [dist.location for dist in working_set]
     path.extend(extra_paths)
-    path = repr(path)[1:-1].replace(', ', ',\n  ')
+    path = map(realpath, path)
+
     generated = []
 
     if isinstance(reqs, str):
@@ -948,19 +951,87 @@ def scripts(reqs, working_set, executable, dest,
             sname = name
 
         sname = os.path.join(dest, sname)
+        spath, rpsetup = _relative_path_and_setup(sname, path, relative_paths)
+
         generated.extend(
-            _script(module_name, attrs, path, sname, executable, arguments,
-                    initialization)
+            _script(module_name, attrs, spath, sname, executable, arguments,
+                    initialization, rpsetup)
             )
 
     if interpreter:
         sname = os.path.join(dest, interpreter)
-        generated.extend(_pyscript(path, sname, executable))
+        spath, rpsetup = _relative_path_and_setup(sname, path, relative_paths)
+        generated.extend(_pyscript(spath, sname, executable, rpsetup))
 
     return generated
 
+def _relative_path_and_setup(sname, path, relative_paths):
+    if relative_paths:
+        sname = os.path.abspath(sname)
+        spath = ',\n  '.join(
+            [_relativitize(path_item, sname, relative_paths)
+             for path_item in path]
+            )
+        rpsetup = relative_paths_setup
+    else:
+        spath = repr(path)[1:-1].replace(', ', ',\n  ')
+        rpsetup = ''
+    return spath, rpsetup
+
+
+def _relative_depth(common, path):
+    n = 0
+    while 1:
+        dirname = os.path.dirname(path)
+        if dirname == path:
+            raise AssertionError("dirname of %s is the same" % dirname)
+        if dirname == common:
+            break
+        n += 1
+        path = dirname
+    return n
+
+def _relative_path(common, path):
+    r = []
+    while 1:
+        dirname, basename = os.path.split(path)
+        r.append(basename)
+        if dirname == common:
+            break
+        if dirname == path:
+            raise AssertionError("dirname of %s is the same" % dirname)
+        path = dirname
+    r.reverse()
+    return os.path.join(*r)
+
+def _relativitize(path, script, relative_paths):
+    if path == script:
+        raise AssertionError("path == script")
+    common = os.path.dirname(os.path.commonprefix([path, script]))
+    if (common == relative_paths or
+        common.startswith(os.path.join(relative_paths, ''))
+        ):
+        return "join(dirname(%s, __file__), %r)" % (
+            _relative_depth(common, script), _relative_path(common, path)
+            )
+    else:
+        return repr(path)
+
+
+relative_paths_setup = """
+import os
+
+def dirname(n, path):
+    while n >= 0:
+        n -= 1
+        path = os.path.dirname(path)
+    return path
+
+join = os.path.join
+"""
+
 def _script(module_name, attrs, path, dest, executable, arguments,
-            initialization):
+            initialization, rsetup):
     generated = []
     script = dest
     if is_win32:
@@ -973,6 +1044,7 @@ def _script(module_name, attrs, path, dest, executable, arguments,
         attrs = attrs,
         arguments = arguments,
         initialization = initialization,
+        relative_paths_setup = rsetup,
         )
     changed = not (os.path.exists(dest) and open(dest).read() == contents)
 
@@ -1002,9 +1074,10 @@ if is_jython and jython_os_name == 'linux':
 else:
     script_header = '#!%(python)s'
 
-script_template = script_header + '''\
 
+script_template = script_header + '''\
 
+%(relative_paths_setup)s
 import sys
 sys.path[0:0] = [
   %(path)s,
@@ -1017,7 +1090,7 @@ if __name__ == '__main__':
 '''
 
 
-def _pyscript(path, dest, executable):
+def _pyscript(path, dest, executable, rsetup):
     generated = []
     script = dest
     if is_win32:
@@ -1026,6 +1099,7 @@ def _pyscript(path, dest, executable):
     contents = py_script_template % dict(
         python = _safe_arg(executable),
         path = path,
+        relative_paths_setup = rsetup,
         )
     changed = not (os.path.exists(dest) and open(dest).read() == contents)
 
@@ -1051,6 +1125,7 @@ def _pyscript(path, dest, executable):
 py_script_template = script_header + '''\
 
 
+%(relative_paths_setup)s
 import sys
 
 sys.path[0:0] = [

src/zc/buildout/easy_install.txt

@@ -89,6 +89,11 @@ use_dependency_links
    for using dependency_links in preference to other
    locations. Defaults to true.
 
+relative_paths
+   Adjust egg paths so they are relative to the script path.  This
+   allows scripts to work when scripts and eggs are moved, as long as
+   they are both moved in the same way.
+
 The install method returns a working set containing the distributions
 needed to meet the given requirements.
 
@@ -781,6 +786,107 @@ You can also pass script initialization code:
     if __name__ == '__main__':
         eggrecipedemo.main(1, 2)
 
+Relative paths
+--------------
+
+Sometimes, you want to be able to move a buildout directory around and
+have scripts still work without having to rebuild them.  We can
+control this using the relative_paths option to install.  You need
+to pass a common base directory of the scripts and eggs:
+
+    >>> bo = tmpdir('bo')
+    >>> mkdir(bo, 'eggs')
+    >>> mkdir(bo, 'bin')
+    >>> mkdir(bo, 'other')
+
+    >>> ws = zc.buildout.easy_install.install(
+    ...     ['demo'], join(bo, 'eggs'), links=[link_server],
+    ...     index=link_server+'index/')
+
+    >>> scripts = zc.buildout.easy_install.scripts(
+    ...    ['demo'], ws, sys.executable, join(bo, 'bin'), dict(demo='run'),
+    ...    extra_paths=[os.path.sep+'foo', join(bo, 'bar')],
+    ...    interpreter='py',
+    ...    relative_paths=bo)
+
+    >>> cat(bo, 'bin', 'run')
+    #!/usr/local/bin/python2.4
+    <BLANKLINE>
+    import os
+    <BLANKLINE>
+    def dirname(n, path):
+        while n >= 0:
+            n -= 1
+            path = os.path.dirname(path)
+        return path
+    <BLANKLINE>
+    join = os.path.join
+    <BLANKLINE>
+    import sys
+    sys.path[0:0] = [
+      join(dirname(1, __file__), 'eggs/demo-0.3-py2.4.egg'),
+      join(dirname(1, __file__), 'eggs/demoneeded-1.1-py2.4.egg'),
+      '/foo',
+      join(dirname(1, __file__), 'bar'),
+      ]
+    <BLANKLINE>
+    import eggrecipedemo
+    <BLANKLINE>
+    if __name__ == '__main__':
+        eggrecipedemo.main()
+
+Note that the extra path we specified that was outside the directory
+passed as relative_paths wasn't converted to a relative path.
+
+Of course, running the script works:
+
+    >>> print system(join(bo, 'bin', 'run')),
+    3 1
+
+We specified an interpreter and its paths are adjusted too:
+
+    >>> cat(bo, 'bin', 'py')
+    #!/usr/local/bin/python2.4
+    <BLANKLINE>
+    <BLANKLINE>
+    import os
+    <BLANKLINE>
+    def dirname(n, path):
+        while n >= 0:
+            n -= 1
+            path = os.path.dirname(path)
+        return path
+    <BLANKLINE>
+    join = os.path.join
+    <BLANKLINE>
+    import sys
+    <BLANKLINE>
+    sys.path[0:0] = [
+      join(dirname(1, __file__), 'eggs/demo-0.3-py2.4.egg'),
+      join(dirname(1, __file__), 'eggs/demoneeded-1.1-py2.4.egg'),
+      '/foo',
+      join(dirname(1, __file__), 'bar'),
+      ]
+    <BLANKLINE>
+    _interactive = True
+    if len(sys.argv) > 1:
+        import getopt
+        _options, _args = getopt.getopt(sys.argv[1:], 'ic:')
+        _interactive = False
+        for (_opt, _val) in _options:
+            if _opt == '-i':
+                _interactive = True
+            elif _opt == '-c':
+                exec _val
+    <BLANKLINE>
+        if _args:
+            sys.argv[:] = _args
+            execfile(sys.argv[0])
+    <BLANKLINE>
+    if _interactive:
+        import code
+        code.interact(banner="", local=globals())
+
 
 Handling custom build options for extensions provided in source distributions
 -----------------------------------------------------------------------------