Edit

[EDIT] FILE: Glue.py

import re
import sys
import types

class GlueError(Exception):
    pass

class RecursionError(GlueError):
    pass

class NoSuchAttributeError(GlueError):
    pass

def ispackage(m):
    """ Determine if a module is a package - that means, sub-modules can be imported
    Currently uses that it has a file name that matches '.*__init__.py[co]?$'
    xxx is this portable/future-safe?

"""
    try:
        name = m.__file__
    except AttributeError:
        return 0
    return re.match('.*__init__.py[co]?$', name)

def dotname(first, last):
    if first and last:
        return '%s.%s' % (first, last)
    else:
        return first + last

class Interface(object):
    def __init__(self, share, owner, name):
        self.__dict__['_share'] = share
        self.__dict__['_owner'] = owner
        self.__dict__['_name'] = name
        for name in share.preload:
            getattr(self, name)

def _import(self, *names):
        return ','.join(names) + '=' + ','.join(['self._root.%s' % name for name in names])

def __getattr__(self, name):
        return self._share.getattr(self, name)

def __setattr__(self, name, value):
        return self._share.setattr(self, name, value)

class Owner:
    def __init__(self, name):
        self.name = name
        self.galog = {}
        self.salog = {}
        self.inters = {}

def log_getattr(self, cache, name):
        name = dotname(cache['_name'], name)
        self.galog[name] = 1

def log_setattr(self, name):
        self.salog[name] = 1

def makeInterface(self, cache, share, name):
        name = dotname(cache['_name'], name)
        if share not in self.inters:
            Clamp = share.Clamp
            if Clamp is not None and issubclass(Clamp, Interface):
                NewInterface = Clamp
            else:
                NewInterface = Interface
            self.inters[share] = NewInterface(share, self, name)
        return self.inters[share]

def pp(self, out=None, short=0):
        if out is None:
            out = sys.stdout
        if not short:
            print('Attributes used by %s:' % self.name, file=out)
            print(self.name[:self.name.rindex('.')+1], file=out)
        complete = []
        for a in self.galog:
            for b in self.galog:
                if a != b and b.startswith(a):
                    break
            else:
                complete.append(a)
        complete.sort()
        for a in complete:
            print('    ', a)

class Share:
    __slots__ = ('module', 'parent', 'name', 'Clamp', 'setable', 'chgable',
                 'importedfrom', 'nowrap', 'wrapattr', 'wrapping', 'data',
                 'owners', 'ispackage', 'recursion', 'preload')
    has_getattr_logging_enabled = False

def __init__(self, module, parent, name, Clamp):
        if parent is None:
            parent = self
            root = self
        else:
            root = parent.data['_root']
        self.module = module
        self.parent = parent
        self.name = name
        self.Clamp = Clamp

self.setable = getattr(Clamp, '_setable_', ())
        if not isinstance(self.setable, tuple):
            raise TypeError(self.message(
                'the _setable_ attribute must be a tuple'))

self.chgable = getattr(Clamp, '_chgable_', ())
        if not isinstance(self.chgable, tuple):
            raise TypeError(self.message(
                'the _chgable_ attribute must be a tuple'))

if Clamp is not None:
            for attr in Clamp.__dict__:
                if attr.startswith('_set_'):
                    attr = attr[len('_set_'):]
                    if attr not in self.setable and attr not in self.chgable:
                        raise TypeError(self.message(
                            '%s must be in either _setable_ or _chgable_ '
                            'for _set_%s to work' % (attr, attr)))

imports = getattr(Clamp, '_imports_', ())
        if not isinstance(imports, tuple):
            raise TypeError(self.message(
                'the _imports_ attribute must be a tuple'))
        self.importedfrom = {}
        pres = {}
        parent_inter = root_inter = None
        for fi in imports:
            presuf = fi.split(':')
            if len(presuf) != 2:
                if len(presuf) > 2:
                    s = "Too many"
                else:
                    s = "No"
                raise SyntaxError("%s ':' in import directive %r." % (s, fi))
            pre, suf = presuf
            pre = pre.strip()
            prepa = pres.get(pre)
            if prepa is None:
                hdta = pre.split('.', 1)
                hd = hdta[0]
                if hd == '_parent':
                    if parent_inter is None:
                        parent_inter = Owner('').makeInterface(
                            {'_name': ''}, parent, '')
                    hdo = parent_inter
                elif hd == '_root':
                    if root_inter is None:
                        root_inter = Owner('').makeInterface(
                            {'_name': ''}, root, '')
                    hdo = root_inter
                else:
                    raise SyntaxError(
                        "Module must begin with _parent or _root")
                if len(hdta) == 2:
                    prepa = [hdo, hdta[1], None]
                else:
                    prepa = [hdo, '', hdo]
                pres[pre] = prepa

sufs = suf.split(',')
            for su in sufs:
                su = su.strip()
                im = getattr(Clamp, '_get_%s' % su, None)
                if im is not None:
                    raise ValueError(
                        'Cant have both name (=%r) in boht importfrom  and _get' % su)

self.importedfrom[su] = prepa

self.nowrap = getattr(Clamp, '_nowrap_', ())
        if not isinstance(self.nowrap, tuple):
            raise TypeError(self.message(
                'the _nowrap_ attribute must be a tuple'))
        wrapattr = getattr(Clamp, '_wrapattr_', None)
        if not isinstance(wrapattr, types.FunctionType) and wrapattr is not None:
            raise TypeError(self.message(
                'the _wrapattr_ attribute must be a method'))
        self.wrapattr = wrapattr
        self.wrapping = 0
        self.data = {}
        self.owners = {}
        self.ispackage = module is None or ispackage(module)
        self.data['_parent'] = parent
        self.data['_root'] = root
        self.data['_module'] = module
        self.recursion = 0

preload = getattr(Clamp, '_preload_', ())
        if preload:
            self.preload = ()
            inter = Owner('').makeInterface({'_name': ''}, self, '')
            for name in preload:
                getattr(inter, name)
        for name in preload:
            assert name in self.data
        self.preload = preload

def message(self, msg):
        return '%s: in %r: %s' % (self.__class__, self.name, msg)

def getattr(self, inter, name):
        owner = inter._owner
        cache = inter.__dict__
        d = self.getattr2(inter, cache, owner, name)
        if name not in self.chgable:
            cache[name] = d
        return d

def getattr2(self, inter, cache, owner, name):
        if self.has_getattr_logging_enabled:
            owner.log_getattr(cache, name)

if name not in self.data:
            try:
                self.recursion += 1
                try:
                    if self.ispackage:
                        try:
                            x = self.getattr3(inter, name)
                        except NoSuchAttributeError:
                            x = self.getattr_package(inter, name)
                    else:
                        x = self.getattr3(inter, name)
                except NoSuchAttributeError:
                    if name == '__repr__':
                        return lambda: str(inter)
                    elif name == '__str__':
                        return lambda: '<%s interface at %s>' % (inter._name,
                                                                 hex(id(self)))
                    else:
                        x = self.getattr_module(inter, name)
                wrapattr = self.wrapattr
                if wrapattr is not None and name not in self.nowrap:
                    assert not self.wrapping
                    try:
                        self.wrapping = 1
                        x = wrapattr(inter, x, name)
                    finally:
                        self.wrapping = 0
                self.data[name] = x
            finally:
                self.recursion -= 1

x = self.data[name]
        if isinstance(x, Share):
            x = owner.makeInterface(cache, x, name)
        return x

def getattr_module(self, inter, name):
        try:
            return getattr(self.module, name)
        except AttributeError:
            raise AttributeError('Module %r or its _GLUECLAMP_ has no attribute %r' % (
                self.module.__name__, name))

def getattr_package(self, inter, name):
        try:
            x = __import__(self.makeName(name))
        except ImportError as exc:
            if (exc.args[0] != 'No module named \'%s\'' % self.makeName(name) or
                    (not self.module and name not in ('__repr__', '__str__'))):
                raise
            x = self.getattr3(inter, name)
            # raise AttributeError, name
        else:
            if self.module:
                x = self.getattr_module(inter, name)
        if isinstance(x, types.ModuleType):
            x = self.makeModule(x, name)
        return x

def getattr3(self, inter, name):
        if self.recursion >= 10:
            raise RecursionError(name)
        Clamp = self.Clamp
        if Clamp is None:
            raise NoSuchAttributeError(name)

try:
            x = getattr(Clamp, name)
        except AttributeError:
            pass
        else:
            if isinstance(x, types.FunctionType):
                x = types.MethodType(x, inter)
            return x

try:
            im = getattr(Clamp, '_get_%s' % name)
        except AttributeError:
            pass
        else:
            owner = self.makeOwner(name)
            inter = Interface(self, owner, '')
            f = types.MethodType(im, inter)
            x = f()
            if isinstance(x, Interface):
                x = x.__dict__['_share']
            return x

if name in self.importedfrom:
            prepa = self.importedfrom[name]
            hdo, ta, pa = prepa
            if pa is None:
                pa = hdo
                tas = ta.split('.')
                for at in tas:
                    pa = getattr(pa, at)
                prepa[2] = pa
            x = getattr(pa, name)
            return x

gp = getattr(Clamp, '_GLUEPATH_', None)
        if gp is None:
            raise NoSuchAttributeError(name)
        if hasattr(gp, 'split'):
            gp = gp.split(',')
        for a in gp:
            a = a.strip()
            bs = a.split('.')
            ii = inter
            for b in bs:
                b = b.strip()
                ii = getattr(ii, b)
            try:
                x = getattr(ii, name)
            except AttributeError:
                continue
            else:
                return x
        raise NoSuchAttributeError(name)

def makeModule(self, module, name):
        Clamp = getattr(module, '_GLUECLAMP_', None)
        return Share(module, self, module.__name__, Clamp)

def makeName(self, name):
        if self.name:
            name = '%s.%s' % (self.name, name)
        return name

def makeOwner(self, name):
        owner_name = self.makeName(name)
        owner = Owner(owner_name)
        self.owners[owner_name] = owner
        return owner

def pp(self, out=sys.stdout):
        if not self.owners:
            return
        print('Dependencies found for %s' % self.name, file=out)
        print('-----------------------'+'-'*len(self.name), file=out)
        keys = list(self.owners.keys())
        keys.sort()
        for key in keys:
            lastname = key[key.rindex('.')+1:]
            print(lastname, file=out)
            self.owners[key].pp(short=1)
        print(file=out)

def rpp(self, out=sys.stdout):
        self.pp(out)
        for k, d in list(self.data.items()):
            if k not in ('_root', '_parent'):
                if isinstance(d, Share):
                    d.rpp()

def setattr(self, inter, name, value):
        Clamp = self.Clamp
        if Clamp is None:
            raise ValueError(
                'Can not change attribute %r because no _GLUECLAMP_ defined.' % name)

setable = self.setable
        chgable = self.chgable
        if (name not in setable and name not in chgable and
                (not (name in self.data and self.data[name] is value))):
            raise ValueError("""Can not change attribute %r,
because it is not in _setable_ or _chgable_.""" % name)
        if name in self.data and self.data[name] is not value and name not in chgable:
            raise ValueError("""Can not change attribute %r,
because it is already set and not in _chgable_.""" % name)

im = getattr(Clamp, '_set_%s' % name, None)
        if im is not None:
            im(inter, value)

self.data[name] = value
        if name not in chgable:  # This is a pain, I suppose. Should we track interfaces?
            inter.__dict__[name] = value

class Test:
    def __init__(self, root):
        self.root = root

class _GLUECLAMP_:
    pass

def Root():
    """\
Create a new guppy Root object.

All functionality in the system may be accessed from this object.
Modules are imported on demand when accessed. Other objects may be
created or imported on demand using Guppy Glue+ directives.
"""
    share = Share(None, None, '', None)
    r = Owner('').makeInterface({'_name': ''}, share, '')
    return r

CANCEL