path: root/src/zope/component/_api.py

##############################################################################
#
# Copyright (c) 2001, 2002 Zope Foundation and Contributors.
# All Rights Reserved.
#
# This software is subject to the provisions of the Zope Public License,
# Version 2.1 (ZPL).  A copy of the ZPL should accompany this distribution.
# THIS SOFTWARE IS PROVIDED "AS IS" AND ANY AND ALL EXPRESS OR IMPLIED
# WARRANTIES ARE DISCLAIMED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
# WARRANTIES OF TITLE, MERCHANTABILITY, AGAINST INFRINGEMENT, AND FITNESS
# FOR A PARTICULAR PURPOSE.
#
##############################################################################
"""Zope 3 Component Architecture
"""
import sys

import zope.interface.interface
from zope.hookable import hookable
from zope.interface import Interface
from zope.interface.interfaces import ComponentLookupError
from zope.interface.interfaces import IComponentLookup

from zope.component.interfaces import IFactory
from zope.component.interfaces import inherits_arch_docs as inherits_docs


# getSiteManager() returns a component registry.  Although the term
# "site manager" is deprecated in favor of "component registry",
# the old term is kept around to maintain a stable API.
base = None


@hookable
@inherits_docs
def getSiteManager(context=None):
    """ See IComponentArchitecture.
    """
    global base
    if context is None:
        if base is None:
            from zope.component.globalregistry import base
        return base
    else:
        # Use the global site manager to adapt context to `IComponentLookup`
        # to avoid the recursion implied by using a local `getAdapter()` call.
        try:
            return IComponentLookup(context)
        except TypeError as error:
            raise ComponentLookupError(*error.args)

# Adapter API


@inherits_docs
def getAdapterInContext(object, interface, context):
    adapter = queryAdapterInContext(object, interface, context)
    if adapter is None:
        raise ComponentLookupError(object, interface)
    return adapter


@inherits_docs
def queryAdapterInContext(object, interface, context, default=None):
    conform = getattr(object, '__conform__', None)
    if conform is not None:
        try:
            adapter = conform(interface)
        except TypeError:
            # We got a TypeError. It might be an error raised by
            # the __conform__ implementation, or *we* may have
            # made the TypeError by calling an unbound method
            # (object is a class).  In the later case, we behave
            # as though there is no __conform__ method. We can
            # detect this case by checking whether there is more
            # than one traceback object in the traceback chain:
            if sys.exc_info()[2].tb_next is not None:
                # There is more than one entry in the chain, so
                # reraise the error:
                raise
            # This clever trick is from Phillip Eby
        else:
            if adapter is not None:
                return adapter

    if interface.providedBy(object):
        return object

    return getSiteManager(context).queryAdapter(object, interface, '', default)


@inherits_docs
def getAdapter(object, interface=Interface, name='', context=None):
    adapter = queryAdapter(object, interface, name, None, context)
    if adapter is None:
        raise ComponentLookupError(object, interface, name)
    return adapter


@inherits_docs
def queryAdapter(object, interface=Interface, name='', default=None,
                 context=None):
    if context is None:
        return adapter_hook(interface, object, name, default)
    return getSiteManager(context).queryAdapter(object, interface, name,
                                                default)


@inherits_docs
def getMultiAdapter(objects, interface=Interface, name='', context=None):
    adapter = queryMultiAdapter(objects, interface, name, context=context)
    if adapter is None:
        raise ComponentLookupError(objects, interface, name)
    return adapter


@inherits_docs
def queryMultiAdapter(objects, interface=Interface, name='', default=None,
                      context=None):
    try:
        sitemanager = getSiteManager(context)
    except ComponentLookupError:
        # Oh blast, no site manager. This should *never* happen!
        return default

    return sitemanager.queryMultiAdapter(objects, interface, name, default)


@inherits_docs
def getAdapters(objects, provided, context=None):
    try:
        sitemanager = getSiteManager(context)
    except ComponentLookupError:
        # Oh blast, no site manager. This should *never* happen!
        return []
    return sitemanager.getAdapters(objects, provided)


@inherits_docs
def subscribers(objects, interface, context=None):
    try:
        sitemanager = getSiteManager(context)
    except ComponentLookupError:
        # Oh blast, no site manager. This should *never* happen!
        return []
    return sitemanager.subscribers(objects, interface)


@inherits_docs
def handle(*objects):
    getSiteManager(None).subscribers(objects, None)

#############################################################################
# Register the component architectures adapter hook, with the adapter hook
# registry of the `zope.inteface` package. This way we will be able to call
# interfaces to create adapters for objects. For example, `I1(ob)` is
# equvalent to `getAdapterInContext(I1, ob, '')`.


@hookable
def adapter_hook(interface, object, name='', default=None):
    try:
        sitemanager = getSiteManager()
    except ComponentLookupError:  # pragma: no cover w/o context, cannot test
        # Oh blast, no site manager. This should *never* happen!
        return None
    return sitemanager.queryAdapter(object, interface, name, default)


zope.interface.interface.adapter_hooks.append(adapter_hook)
#############################################################################


# Utility API
@inherits_docs
def getUtility(interface, name='', context=None):
    utility = queryUtility(interface, name, context=context)
    if utility is not None:
        return utility
    raise ComponentLookupError(interface, name)


@inherits_docs
def queryUtility(interface, name='', default=None, context=None):
    return getSiteManager(context).queryUtility(interface, name, default)


@inherits_docs
def getUtilitiesFor(interface, context=None):
    return getSiteManager(context).getUtilitiesFor(interface)


@inherits_docs
def getAllUtilitiesRegisteredFor(interface, context=None):
    return getSiteManager(context).getAllUtilitiesRegisteredFor(interface)


_marker = object()


@inherits_docs
def queryNextUtility(context, interface, name='', default=None):
    """Query for the next available utility.

    Find the next available utility providing `interface` and having the
    specified name. If no utility was found, return the specified `default`
    value.
    """
    try:
        sm = getSiteManager(context)
    except ComponentLookupError:
        return default
    bases = sm.__bases__
    for base in bases:
        util = base.queryUtility(interface, name, _marker)
        if util is not _marker:
            return util
    return default


@inherits_docs
def getNextUtility(context, interface, name=''):
    """Get the next available utility.

    If no utility was found, a `ComponentLookupError` is raised.
    """
    util = queryNextUtility(context, interface, name, _marker)
    if util is _marker:
        raise ComponentLookupError(
            "No more utilities for {}, '{}' have been found.".format(
                interface, name))
    return util


# Factories

@inherits_docs
def createObject(__factory_name, *args, **kwargs):
    """Invoke the named factory and return the result.

    ``__factory_name`` is a positional-only argument.
    """
    context = kwargs.pop('context', None)
    return getUtility(IFactory, __factory_name, context)(*args, **kwargs)


@inherits_docs
def getFactoryInterfaces(name, context=None):
    """Return the interface provided by the named factory's objects

    Result might be a single interface. XXX
    """
    return getUtility(IFactory, name, context).getInterfaces()


@inherits_docs
def getFactoriesFor(interface, context=None):
    """Return info on all factories implementing the given interface.
    """
    utils = getSiteManager(context)
    for (name, factory) in utils.getUtilitiesFor(IFactory):
        interfaces = factory.getInterfaces()
        try:
            if interfaces.isOrExtends(interface):
                yield name, factory
        except AttributeError:
            for iface in interfaces:
                if iface.isOrExtends(interface):
                    yield name, factory
                    break