Automatic inclusion of package dependencies
===========================================

The z3c.autoinclude.dependency module uses an egg's install_requires
information (in the project's setup.py) to find and implicitly load
zcml from all dependencies of a project.

We have created a test environment to simulate setuptools
dependencies.

``APackage`` depends on ``BCPackage``
``BCPackage`` depends on ``SiblingPackage``

Given the distribution for the project named ``APackage``, we can ask
for the requirements of that distribution::

    >>> import a
    >>> from z3c.autoinclude.utils import distributionForPackage
    >>> a_dist = distributionForPackage(a)

    >>> reqs = a_dist.requires()
    >>> pprint(sorted(reqs, key=lambda r:r.project_name))
    [Requirement.parse('BCPackage'),
     Requirement.parse('TestDirective'),
     Requirement.parse('z3c.autoinclude')]

We can turn this requirement into a distribution::

    >>> from pkg_resources import get_provider
    >>> b_dist = get_provider(reqs[0])

We can adapt a distribution to a DependencyFinder::

    >>> from z3c.autoinclude.dependency import DependencyFinder
    >>> a_include_finder = DependencyFinder(a_dist)
    >>> b_include_finder = DependencyFinder(b_dist)
    
    >>> import x.y.z
    >>> xyz_dist = distributionForPackage(x.y.z)
    >>> xyz_include_finder = DependencyFinder(xyz_dist)

    >>> import F.G
    >>> sibling_dist = distributionForPackage(F.G)
    >>> sibling_include_finder = DependencyFinder(sibling_dist)

The include finder provides functionality to determine what namespace
packages exist in the distribution. In the case of ``APackage``, there
are no namespace packages::

    >>> a_include_finder.namespaceDottedNames()
    []

``BPackage`` does have a namespace package, ``b``::

    >>> b_include_finder.namespaceDottedNames()
    ['b']

``XYZPackage`` has a namespace package too, ``x.y`` (``x`` is also
a namespace package)::

    >>> xyz_include_finder.namespaceDottedNames()
    ['x', 'x.y']

We can also get the dotted names of the actual packages that we want
to inspect in a distribution. For a project without namespace packages,
this will be the packages directly in the packages::

    >>> a_include_finder.dottedNames()
    ['a']

For a project with namespace packages, it will be the packages that
are in the namespace packages::

    >>> b_include_finder.dottedNames()
    ['b.c']

For a nested namespace package, it should still be the innermost package::

    >>> xyz_include_finder.dottedNames()
    ['x.y.z']

What we need to know in the end is which packages in the requirements
of a distribution have files we want to include (``configure.zcml``,
``meta.zcml``). So, given a distribution, let's retrieve all packages
that it depends on that have ``configure.zcml`` or ``meta.zcml``.
Note that the individual lists within ``includableInfo`` preserve the
package order defined in ``setup.py``::

    >>> a_include_finder.includableInfo(['configure.zcml', 'meta.zcml'])
    {'configure.zcml': ['b.c'], 'meta.zcml': ['z3c.autoinclude', 'testdirective']}

For a nested namespace package with two siblings ``SiblingPackage``,
we should get the same expected results. The sibling package
``SiblingPackage`` does have a namespace package::

    >>> sibling_include_finder.namespaceDottedNames()
    ['F']

For a namespace package with 2 sibling namespaces, we get both sibling
packages::

    >>> sibling_include_finder.dottedNames()
    ['F.G', 'F.H']

And we should be able to pick up the files we need to include from
both dotted names::

    >>> pprint(b_include_finder.includableInfo(['configure.zcml',
    ...                                         'meta.zcml']))
    {'configure.zcml': ['F.H'], 'meta.zcml': ['testdirective', 'F.G', 'F.H']}

``APackage`` depends on ``BCPackage``, which depends on
``SiblingPackage``. ``APackage`` and ``BCPackage`` both contain the
autoinclude directive, which will automatically include any meta.zcml
and configure.zcml files (in that order) that their dependencies
contain. These dependencies' zcml actually contain a test directive
that will append a logging message to a global variable in
testdirective.zcml. So let's trigger the loading of the configure.zcml
in ``APackage`` and see whether its ``BCPackage`` dependency, and
``BCPackage``'s dependencies, were indeed loaded and in the correct
order::

    >>> from pkg_resources import resource_filename
    >>> from zope.configuration import xmlconfig
    >>> import a
    >>> dummy = xmlconfig.file(resource_filename('a', 'configure.zcml'),
    ...                        package=a)
    >>> from testdirective.zcml import test_log
    >>> pprint(test_log)
    [u'f.g meta has been loaded',
     u'f.h has been loaded',
     u'BCPackage has been loaded']

There is also a directive for including overrides, which calls
``autoIncludeOverridesDirective``; however, I have no idea how to test
this.

Finally, there is a convenience API for finding the files we need to
include from the requirements of a given package::

    >>> from z3c.autoinclude import package_includes
    >>> pprint(package_includes('BCPackage'))
    {'configure.zcml': ['F.H'],
     'meta.zcml': ['testdirective', 'F.G', 'F.H'],
     'overrides.zcml': []}

As with ``includableInfo``, we can also supply a list of ZCML filenames to search for::

    >>> pprint(package_includes('BCPackage', ['configure.zcml', 'silly.zcml']))
    {'configure.zcml': ['F.H'], 'silly.zcml': []}

Note that it will not catch DistributionNotFound errors::

     >>> package_includes('NonexistentPackage')
     Traceback (most recent call last):
     ...
     DistributionNotFound: NonexistentPackage