zope.configuration.zopeconfigure — zope.configuration 4.0 documentation

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# Source code for zope.configuration.zopeconfigure

    ##############################################################################
    #
    # Copyright (c) 2001, 2002, 2003 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 configure directive

    This file contains the implementation of the Zope configure directive.
    It is broken out in a separate file to provide an example of a grouping
    directive.

    The zope configuration directive is a pure grouping directive.  It
    doesn't compute any actions on it's own. Instead, it allows a package
    to be specified, affecting the interpretation of relative dotted names
    and file paths. It also allows an i18n domain to be specified.  The
    information collected is used by subdirectives.

    To define a grouping directive, we need to do three things:

    - Define a schema for the parameters passed to the directive

    - Define a handler class.

    - Register the class

    The parameter schema is given by IZopeConfigure. It specifies a
    package parameter and an i18n_domain parameter.  The package parameter
    is specified as a ``GlobalObject``. This means it must be given as a
    dotted name that can be resolved through import.  The i18n domain is
    just a plain (not unicode) string.

    The handler class has a constructor that takes a context to be adapted
    and zero or more arguments (depending on the paramter schema).  The
    handler class must implement
    ``zope.configuration.interfaces.IGroupingContext``, which defines
    hooks ``before`` and ``after``, that are called with no arguments
    before and after nested directives are processed.  If a grouping
    directive handler creates any actions, or does any computation, this
    is normally done in either the ``before`` or ``after`` hooks.
    Grouping handlers are normally decorators.

    The base class,
    ``zope.configuration.config.GroupingContextDecorator``, is normally
    used to define grouping directive handlers. It provides:

    - An implementation of IConfigurationContext, which grouping directive
      handlers should normally implement,

    - A default implementation of ``IGroupingContext`` that provides empty
      hooks.

    - Decorator support that uses a ``__getattr__`` method to delegate
      attribute accesses to adapted contexts, and

    - A constructor that sets the ``context`` attribute to the adapted
      context and assigns keyword arguments to attributes.

    The ``ZopeConfigure`` provides handling for the ``configure``
    directive. It subclasses GroupingContextDecorator, and overrides the
    constructor to set the ``basepath`` attribute if a ``package`` argument
    is provided. Note that it delegates the job of assigning paramters to
    attribute to the ``GroupingContextDecorator`` constructor.

    The last step is to register the directive using the meta
    configuration directive.  If we wanted to register the Zope
    ``configure`` directive for the ``zope`` namespace, we'd use a
    meta-configuration directive like::

      <meta:groupingDirective
         namespace="http://namespaces.zope.org/zope"
         name="configure"
         schema="zope.configuration.zopeconfigure.IZopeConfigure"
         handler="zope.configuration.zopeconfigure.ZopeConfigure"
         >
         Zope configure

         The ``configure`` node is normally used as the root node for a
         configuration file.  It can also be used to specify a package or
         internationalization domain for a group of directives within a
         file by grouping those directives.
      </meta:groupingDirective>

    We use the groupingDirective meta-directive to register a grouping
    directive. The parameters are self explanatory.  The textual contents
    of the directive provide documentation text, excluding parameter
    documentation, which is provided by the schema.

    (The Zope ``configuration`` directive is actually registered using a
    lower-level Python API because it is registered for all namespaces,
    which isn't supported using the meta-configuration directives.)
    """
    __docformat__ = 'restructuredtext'
    import os

    from zope.interface import Interface
    from zope.schema import BytesLine

    from zope.configuration.config import GroupingContextDecorator
    from zope.configuration.fields import GlobalObject
    from zope.configuration._compat import u

    class IZopeConfigure(Interface):
        """The ``zope:configure`` Directive

        The zope configuration directive is a pure grouping directive.  It
        doesn't compute any actions on it's own. Instead, it allows a package to
        be specified, affecting the interpretation of relative dotted names and
        file paths. It also allows an i18n domain to be specified.  The
        information collected is used by subdirectives.

        It may seem that this directive can only be used once per file, but it can
        be applied whereever it is convenient.
        """

        package = GlobalObject(
            title=u("Package"),
            description=u("The package to be used for evaluating relative imports "
                          "and file names."),
            required=False)

        i18n_domain = BytesLine(
            title=u("Internationalization domain"),
            description=u("This is a name for the software project. It must be a "
                          "legal file-system name as it will be used to contruct "
                          "names for directories containing translation data. "
                          "\n"
                          "The domain defines a namespace for the message ids "
                          "used by a project."),
            required=False)

    class ZopeConfigure(GroupingContextDecorator):
        __doc__ = __doc__

        def __init__(self, context, **kw):
            super(ZopeConfigure, self).__init__(context, **kw)
            if 'package' in kw:
                # if we have a package, we want to also define basepath
                # so we don't acquire one
                self.basepath = os.path.dirname(self.package.__file__)

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