add support for using an absolute path to override an asset

fixes #1229

5 files changed, 496 insertions, 166 deletions

diff --git a/CHANGES.txt b/CHANGES.txt
index 434eab898..2350bb3de 100644
--- a/CHANGES.txt
+++ b/CHANGES.txt
@@ -1,3 +1,7 @@
+- Assets can now be overidden by an absolute path on the filesystem when using
+  the ``config.override_asset`` API.
+  See https://github.com/Pylons/pyramid/issues/1229
+
 Unreleased
 ==========
 
diff --git a/docs/narr/assets.rst b/docs/narr/assets.rst
index b0a8d18b0..fec55ce7c 100644
--- a/docs/narr/assets.rst
+++ b/docs/narr/assets.rst
@@ -526,3 +526,6 @@ files.  Any software which uses the
 :func:`pkg_resources.get_resource_string` APIs will obtain an overridden file
 when an override is used.
 
+As of Pyramid 1.6, it is also possible to override an asset by supplying an
+absolute path to a file or directory. This may be useful if the assets are
+not distributed as part of a Python package.
diff --git a/pyramid/config/assets.py b/pyramid/config/assets.py
index 0616e6cda..9da092f08 100644
--- a/pyramid/config/assets.py
+++ b/pyramid/config/assets.py
@@ -1,3 +1,4 @@
+import os
 import pkg_resources
 import sys
 
@@ -79,7 +80,8 @@ class OverrideProvider(pkg_resources.DefaultProvider):
                 return result
         return pkg_resources.DefaultProvider.resource_listdir(
             self, resource_name)
-        
+
+
 @implementer(IPackageOverrides)
 class PackageOverrides(object):
     # pkg_resources arg in kw args below for testing
@@ -97,57 +99,61 @@ class PackageOverrides(object):
         # optional)...
         # A __loader__ attribute is basically metadata, and setuptools
         # uses it as such.
-        package.__loader__ = self 
+        package.__loader__ = self
         # we call register_loader_type for every instantiation of this
         # class; that's OK, it's idempotent to do it more than once.
         pkg_resources.register_loader_type(self.__class__, OverrideProvider)
         self.overrides = []
         self.overridden_package_name = package.__name__
 
-    def insert(self, path, package, prefix):
+    def insert(self, path, source):
         if not path or path.endswith('/'):
-            override = DirectoryOverride(path, package, prefix)
+            override = DirectoryOverride(path, source)
         else:
-            override = FileOverride(path, package, prefix)
+            override = FileOverride(path, source)
         self.overrides.insert(0, override)
         return override
 
-    def search_path(self, resource_name):
+    def filtered_sources(self, resource_name):
         for override in self.overrides:
             o = override(resource_name)
             if o is not None:
-                package, name = o
-                yield package, name
+                yield o
 
     def get_filename(self, resource_name):
-        for package, rname in self.search_path(resource_name):
-            if pkg_resources.resource_exists(package, rname):
-                return pkg_resources.resource_filename(package, rname)
+        for source, path in self.filtered_sources(resource_name):
+            result = source.get_filename(path)
+            if result is not None:
+                return result
 
     def get_stream(self, resource_name):
-        for package, rname in self.search_path(resource_name):
-            if pkg_resources.resource_exists(package, rname):
-                return pkg_resources.resource_stream(package, rname)
+        for source, path in self.filtered_sources(resource_name):
+            result = source.get_stream(path)
+            if result is not None:
+                return result
 
     def get_string(self, resource_name):
-        for package, rname in self.search_path(resource_name):
-            if pkg_resources.resource_exists(package, rname):
-                return pkg_resources.resource_string(package, rname)
+        for source, path in self.filtered_sources(resource_name):
+            result = source.get_string(path)
+            if result is not None:
+                return result
 
     def has_resource(self, resource_name):
-        for package, rname in self.search_path(resource_name):
-            if pkg_resources.resource_exists(package, rname):
+        for source, path in self.filtered_sources(resource_name):
+            if source.exists(path):
                 return True
 
     def isdir(self, resource_name):
-        for package, rname in self.search_path(resource_name):
-            if pkg_resources.resource_exists(package, rname):
-                return pkg_resources.resource_isdir(package, rname)
+        for source, path in self.filtered_sources(resource_name):
+            result = source.isdir(path)
+            if result is not None:
+                return result
 
     def listdir(self, resource_name):
-        for package, rname in self.search_path(resource_name):
-            if pkg_resources.resource_exists(package, rname):
-                return pkg_resources.resource_listdir(package, rname)
+        for source, path in self.filtered_sources(resource_name):
+            result = source.listdir(path)
+            if result is not None:
+                return result
 
     @property
     def real_loader(self):
@@ -174,72 +180,180 @@ class PackageOverrides(object):
         """ See IPEP302Loader.
         """
         return self.real_loader.get_source(fullname)
- 
+
 
 class DirectoryOverride:
-    def __init__(self, path, package, prefix):
+    def __init__(self, path, source):
         self.path = path
-        self.package = package
-        self.prefix = prefix
         self.pathlen = len(self.path)
+        self.source = source
 
     def __call__(self, resource_name):
         if resource_name.startswith(self.path):
-            name = '%s%s' % (self.prefix, resource_name[self.pathlen:])
-            return self.package, name
+            new_path = resource_name[self.pathlen:]
+            return self.source, new_path
 
 class FileOverride:
-    def __init__(self, path, package, prefix):
+    def __init__(self, path, source):
         self.path = path
-        self.package = package
-        self.prefix = prefix
+        self.source = source
 
     def __call__(self, resource_name):
         if resource_name == self.path:
-            return self.package, self.prefix
+            return self.source, ''
+
+
+class PackageAssetSource(object):
+    """
+    An asset source relative to a package.
+
+    If this asset source is a file, then we expect the ``prefix`` to point
+    to the new name of the file, and the incoming ``resource_name`` will be
+    the empty string, as returned by the ``FileOverride``.
+
+    """
+    def __init__(self, package, prefix):
+        self.package = package
+        self.prefix = prefix
+
+    def get_path(self, resource_name):
+        return '%s%s' % (self.prefix, resource_name)
+
+    def get_filename(self, resource_name):
+        path = self.get_path(resource_name)
+        if pkg_resources.resource_exists(self.package, path):
+            return pkg_resources.resource_filename(self.package, path)
+
+    def get_stream(self, resource_name):
+        path = self.get_path(resource_name)
+        if pkg_resources.resource_exists(self.package, path):
+            return pkg_resources.resource_stream(self.package, path)
+
+    def get_string(self, resource_name):
+        path = self.get_path(resource_name)
+        if pkg_resources.resource_exists(self.package, path):
+            return pkg_resources.resource_string(self.package, path)
+
+    def exists(self, resource_name):
+        path = self.get_path(resource_name)
+        if pkg_resources.resource_exists(self.package, path):
+            return True
+
+    def isdir(self, resource_name):
+        path = self.get_path(resource_name)
+        if pkg_resources.resource_exists(self.package, path):
+            return pkg_resources.resource_isdir(self.package, path)
+
+    def listdir(self, resource_name):
+        path = self.get_path(resource_name)
+        if pkg_resources.resource_exists(self.package, path):
+            return pkg_resources.resource_listdir(self.package, path)
+
+
+class FSAssetSource(object):
+    """
+    An asset source relative to a path in the filesystem.
+
+    """
+    def __init__(self, prefix):
+        self.prefix = prefix
+
+    def get_filename(self, resource_name):
+        if resource_name:
+            path = os.path.join(self.prefix, resource_name)
+        else:
+            path = self.prefix
+
+        if os.path.exists(path):
+            return path
+
+    def get_stream(self, resource_name):
+        path = self.get_filename(resource_name)
+        if path is not None:
+            return open(path, 'rb')
+
+    def get_string(self, resource_name):
+        stream = self.get_stream(resource_name)
+        if stream is not None:
+            with stream:
+                return stream.read()
+
+    def exists(self, resource_name):
+        path = self.get_filename(resource_name)
+        if path is not None:
+            return True
+
+    def isdir(self, resource_name):
+        path = self.get_filename(resource_name)
+        if path is not None:
+            return os.path.isdir(path)
+
+    def listdir(self, resource_name):
+        path = self.get_filename(resource_name)
+        if path is not None:
+            return os.listdir(path)
 
 
 class AssetsConfiguratorMixin(object):
-    def _override(self, package, path, override_package, override_prefix,
+    def _override(self, package, path, override_source,
                   PackageOverrides=PackageOverrides):
         pkg_name = package.__name__
-        override_pkg_name = override_package.__name__
         override = self.registry.queryUtility(IPackageOverrides, name=pkg_name)
         if override is None:
             override = PackageOverrides(package)
             self.registry.registerUtility(override, IPackageOverrides,
                                           name=pkg_name)
-        override.insert(path, override_pkg_name, override_prefix)
+        override.insert(path, override_source)
 
     @action_method
     def override_asset(self, to_override, override_with, _override=None):
         """ Add a :app:`Pyramid` asset override to the current
         configuration state.
 
-        ``to_override`` is a :term:`asset specification` to the
+        ``to_override`` is an :term:`asset specification` to the
         asset being overridden.
 
-        ``override_with`` is a :term:`asset specification` to the
-        asset that is performing the override.
+        ``override_with`` is an :term:`asset specification` to the
+        asset that is performing the override. This may also be an absolute
+        path.
 
         See :ref:`assets_chapter` for more
         information about asset overrides."""
         if to_override == override_with:
-            raise ConfigurationError('You cannot override an asset with itself')
+            raise ConfigurationError(
+                'You cannot override an asset with itself')
 
         package = to_override
         path = ''
         if ':' in to_override:
             package, path = to_override.split(':', 1)
 
-        override_package = override_with
-        override_prefix = ''
-        if ':' in override_with:
-            override_package, override_prefix = override_with.split(':', 1)
-
         # *_isdir = override is package or directory
-        overridden_isdir = path=='' or path.endswith('/') 
-        override_isdir = override_prefix=='' or override_prefix.endswith('/')
+        overridden_isdir = path == '' or path.endswith('/')
+
+        if os.path.isabs(override_with):
+            override_source = FSAssetSource(override_with)
+            if not os.path.exists(override_with):
+                raise ConfigurationError(
+                    'Cannot override asset with an absolute path that does '
+                    'not exist')
+            override_isdir = os.path.isdir(override_with)
+            override_package = None
+            override_prefix = override_with
+        else:
+            override_package = override_with
+            override_prefix = ''
+            if ':' in override_with:
+                override_package, override_prefix = override_with.split(':', 1)
+
+            __import__(override_package)
+            to_package = sys.modules[override_package]
+            override_source = PackageAssetSource(to_package, override_prefix)
+
+            override_isdir = (
+                override_prefix == '' or
+                override_with.endswith('/')
+            )
 
         if overridden_isdir and (not override_isdir):
             raise ConfigurationError(
@@ -255,10 +369,8 @@ class AssetsConfiguratorMixin(object):
 
         def register():
             __import__(package)
-            __import__(override_package)
             from_package = sys.modules[package]
-            to_package = sys.modules[override_package]
-            override(from_package, path, to_package, override_prefix)
+            override(from_package, path, override_source)
 
         intr = self.introspectable(
             'asset overrides',
diff --git a/pyramid/tests/test_config/pkgs/asset/subpackage/templates/bar.pt b/pyramid/tests/test_config/pkgs/asset/subpackage/templates/bar.pt
new file mode 100644
index 000000000..e69de29bb
--- /dev/null
+++ b/pyramid/tests/test_config/pkgs/asset/subpackage/templates/bar.pt
diff --git a/pyramid/tests/test_config/test_assets.py b/pyramid/tests/test_config/test_assets.py
index 345e7f8d6..b605a602d 100644
--- a/pyramid/tests/test_config/test_assets.py
+++ b/pyramid/tests/test_config/test_assets.py
@@ -1,6 +1,10 @@
+import os.path
 import unittest
 from pyramid.testing import cleanUp
 
+# we use this folder
+here = os.path.dirname(os.path.abspath(__file__))
+
 class TestAssetsConfiguratorMixin(unittest.TestCase):
     def _makeOne(self, *arg, **kw):
         from pyramid.config import Configurator
@@ -10,27 +14,31 @@ class TestAssetsConfiguratorMixin(unittest.TestCase):
     def test_override_asset_samename(self):
         from pyramid.exceptions import ConfigurationError
         config = self._makeOne()
-        self.assertRaises(ConfigurationError, config.override_asset,'a', 'a')
+        self.assertRaises(ConfigurationError, config.override_asset, 'a', 'a')
 
     def test_override_asset_directory_with_file(self):
         from pyramid.exceptions import ConfigurationError
         config = self._makeOne()
         self.assertRaises(ConfigurationError, config.override_asset,
-                          'a:foo/', 'a:foo.pt')
+                          'a:foo/',
+                          'pyramid.tests.test_config.pkgs.asset:foo.pt')
 
     def test_override_asset_file_with_directory(self):
         from pyramid.exceptions import ConfigurationError
         config = self._makeOne()
         self.assertRaises(ConfigurationError, config.override_asset,
-                          'a:foo.pt', 'a:foo/')
+                          'a:foo.pt',
+                          'pyramid.tests.test_config.pkgs.asset:templates/')
 
     def test_override_asset_file_with_package(self):
         from pyramid.exceptions import ConfigurationError
         config = self._makeOne()
         self.assertRaises(ConfigurationError, config.override_asset,
-                          'a:foo.pt', 'a')
+                          'a:foo.pt',
+                          'pyramid.tests.test_config.pkgs.asset')
 
     def test_override_asset_file_with_file(self):
+        from pyramid.config.assets import PackageAssetSource
         config = self._makeOne(autocommit=True)
         override = DummyUnderOverride()
         config.override_asset(
@@ -41,10 +49,13 @@ class TestAssetsConfiguratorMixin(unittest.TestCase):
         from pyramid.tests.test_config.pkgs.asset import subpackage
         self.assertEqual(override.package, asset)
         self.assertEqual(override.path, 'templates/foo.pt')
-        self.assertEqual(override.override_package, subpackage)
-        self.assertEqual(override.override_prefix, 'templates/bar.pt')
+        source = override.source
+        self.assertTrue(isinstance(source, PackageAssetSource))
+        self.assertEqual(source.package, subpackage)
+        self.assertEqual(source.prefix, 'templates/bar.pt')
 
     def test_override_asset_package_with_package(self):
+        from pyramid.config.assets import PackageAssetSource
         config = self._makeOne(autocommit=True)
         override = DummyUnderOverride()
         config.override_asset(
@@ -55,10 +66,13 @@ class TestAssetsConfiguratorMixin(unittest.TestCase):
         from pyramid.tests.test_config.pkgs.asset import subpackage
         self.assertEqual(override.package, asset)
         self.assertEqual(override.path, '')
-        self.assertEqual(override.override_package, subpackage)
-        self.assertEqual(override.override_prefix, '')
+        source = override.source
+        self.assertTrue(isinstance(source, PackageAssetSource))
+        self.assertEqual(source.package, subpackage)
+        self.assertEqual(source.prefix, '')
 
     def test_override_asset_directory_with_directory(self):
+        from pyramid.config.assets import PackageAssetSource
         config = self._makeOne(autocommit=True)
         override = DummyUnderOverride()
         config.override_asset(
@@ -69,10 +83,13 @@ class TestAssetsConfiguratorMixin(unittest.TestCase):
         from pyramid.tests.test_config.pkgs.asset import subpackage
         self.assertEqual(override.package, asset)
         self.assertEqual(override.path, 'templates/')
-        self.assertEqual(override.override_package, subpackage)
-        self.assertEqual(override.override_prefix, 'templates/')
+        source = override.source
+        self.assertTrue(isinstance(source, PackageAssetSource))
+        self.assertEqual(source.package, subpackage)
+        self.assertEqual(source.prefix, 'templates/')
 
     def test_override_asset_directory_with_package(self):
+        from pyramid.config.assets import PackageAssetSource
         config = self._makeOne(autocommit=True)
         override = DummyUnderOverride()
         config.override_asset(
@@ -83,10 +100,13 @@ class TestAssetsConfiguratorMixin(unittest.TestCase):
         from pyramid.tests.test_config.pkgs.asset import subpackage
         self.assertEqual(override.package, asset)
         self.assertEqual(override.path, 'templates/')
-        self.assertEqual(override.override_package, subpackage)
-        self.assertEqual(override.override_prefix, '')
+        source = override.source
+        self.assertTrue(isinstance(source, PackageAssetSource))
+        self.assertEqual(source.package, subpackage)
+        self.assertEqual(source.prefix, '')
 
     def test_override_asset_package_with_directory(self):
+        from pyramid.config.assets import PackageAssetSource
         config = self._makeOne(autocommit=True)
         override = DummyUnderOverride()
         config.override_asset(
@@ -97,32 +117,105 @@ class TestAssetsConfiguratorMixin(unittest.TestCase):
         from pyramid.tests.test_config.pkgs.asset import subpackage
         self.assertEqual(override.package, asset)
         self.assertEqual(override.path, '')
-        self.assertEqual(override.override_package, subpackage)
-        self.assertEqual(override.override_prefix, 'templates/')
+        source = override.source
+        self.assertTrue(isinstance(source, PackageAssetSource))
+        self.assertEqual(source.package, subpackage)
+        self.assertEqual(source.prefix, 'templates/')
+
+    def test_override_asset_directory_with_absfile(self):
+        from pyramid.exceptions import ConfigurationError
+        config = self._makeOne()
+        self.assertRaises(ConfigurationError, config.override_asset,
+                          'a:foo/',
+                          os.path.join(here, 'pkgs', 'asset', 'foo.pt'))
+
+    def test_override_asset_file_with_absdirectory(self):
+        from pyramid.exceptions import ConfigurationError
+        config = self._makeOne()
+        abspath = os.path.join(here, 'pkgs', 'asset', 'subpackage', 'templates')
+        self.assertRaises(ConfigurationError, config.override_asset,
+                          'a:foo.pt',
+                          abspath)
+
+    def test_override_asset_file_with_missing_abspath(self):
+        from pyramid.exceptions import ConfigurationError
+        config = self._makeOne()
+        self.assertRaises(ConfigurationError, config.override_asset,
+                          'a:foo.pt',
+                          os.path.join(here, 'wont_exist'))
+
+    def test_override_asset_file_with_absfile(self):
+        from pyramid.config.assets import FSAssetSource
+        config = self._makeOne(autocommit=True)
+        override = DummyUnderOverride()
+        abspath = os.path.join(here, 'pkgs', 'asset', 'subpackage',
+                               'templates', 'bar.pt')
+        config.override_asset(
+            'pyramid.tests.test_config.pkgs.asset:templates/foo.pt',
+            abspath,
+            _override=override)
+        from pyramid.tests.test_config.pkgs import asset
+        self.assertEqual(override.package, asset)
+        self.assertEqual(override.path, 'templates/foo.pt')
+        source = override.source
+        self.assertTrue(isinstance(source, FSAssetSource))
+        self.assertEqual(source.prefix, abspath)
+
+    def test_override_asset_directory_with_absdirectory(self):
+        from pyramid.config.assets import FSAssetSource
+        config = self._makeOne(autocommit=True)
+        override = DummyUnderOverride()
+        abspath = os.path.join(here, 'pkgs', 'asset', 'subpackage', 'templates')
+        config.override_asset(
+            'pyramid.tests.test_config.pkgs.asset:templates/',
+            abspath,
+            _override=override)
+        from pyramid.tests.test_config.pkgs import asset
+        self.assertEqual(override.package, asset)
+        self.assertEqual(override.path, 'templates/')
+        source = override.source
+        self.assertTrue(isinstance(source, FSAssetSource))
+        self.assertEqual(source.prefix, abspath)
+
+    def test_override_asset_package_with_absdirectory(self):
+        from pyramid.config.assets import FSAssetSource
+        config = self._makeOne(autocommit=True)
+        override = DummyUnderOverride()
+        abspath = os.path.join(here, 'pkgs', 'asset', 'subpackage', 'templates')
+        config.override_asset(
+            'pyramid.tests.test_config.pkgs.asset',
+            abspath,
+            _override=override)
+        from pyramid.tests.test_config.pkgs import asset
+        self.assertEqual(override.package, asset)
+        self.assertEqual(override.path, '')
+        source = override.source
+        self.assertTrue(isinstance(source, FSAssetSource))
+        self.assertEqual(source.prefix, abspath)
 
     def test__override_not_yet_registered(self):
         from pyramid.interfaces import IPackageOverrides
         package = DummyPackage('package')
-        opackage = DummyPackage('opackage')
+        source = DummyAssetSource()
         config = self._makeOne()
-        config._override(package, 'path', opackage, 'oprefix',
+        config._override(package, 'path', source,
                          PackageOverrides=DummyPackageOverrides)
         overrides = config.registry.queryUtility(IPackageOverrides,
                                                  name='package')
-        self.assertEqual(overrides.inserted, [('path', 'opackage', 'oprefix')])
+        self.assertEqual(overrides.inserted, [('path', source)])
         self.assertEqual(overrides.package, package)
 
     def test__override_already_registered(self):
         from pyramid.interfaces import IPackageOverrides
         package = DummyPackage('package')
-        opackage = DummyPackage('opackage')
+        source = DummyAssetSource()
         overrides = DummyPackageOverrides(package)
         config = self._makeOne()
         config.registry.registerUtility(overrides, IPackageOverrides,
                                         name='package')
-        config._override(package, 'path', opackage, 'oprefix',
+        config._override(package, 'path', source,
                          PackageOverrides=DummyPackageOverrides)
-        self.assertEqual(overrides.inserted, [('path', 'opackage', 'oprefix')])
+        self.assertEqual(overrides.inserted, [('path', source)])
         self.assertEqual(overrides.package, package)
 
 
@@ -148,30 +241,24 @@ class TestOverrideProvider(unittest.TestCase):
         reg.registerUtility(overrides, IPackageOverrides, name=name)
 
     def test_get_resource_filename_no_overrides(self):
-        import os
         resource_name = 'test_assets.py'
         import pyramid.tests.test_config
         provider = self._makeOne(pyramid.tests.test_config)
-        here = os.path.dirname(os.path.abspath(__file__))
         expected = os.path.join(here, resource_name)
         result = provider.get_resource_filename(None, resource_name)
         self.assertEqual(result, expected)
 
     def test_get_resource_stream_no_overrides(self):
-        import os
         resource_name = 'test_assets.py'
         import pyramid.tests.test_config
         provider = self._makeOne(pyramid.tests.test_config)
-        here = os.path.dirname(os.path.abspath(__file__))
         with provider.get_resource_stream(None, resource_name) as result:
             _assertBody(result.read(), os.path.join(here, resource_name))
 
     def test_get_resource_string_no_overrides(self):
-        import os
         resource_name = 'test_assets.py'
         import pyramid.tests.test_config
         provider = self._makeOne(pyramid.tests.test_config)
-        here = os.path.dirname(os.path.abspath(__file__))
         result = provider.get_resource_string(None, resource_name)
         _assertBody(result, os.path.join(here, resource_name))
 
@@ -202,11 +289,9 @@ class TestOverrideProvider(unittest.TestCase):
     def test_get_resource_filename_override_returns_None(self):
         overrides = DummyOverrides(None)
         self._registerOverrides(overrides)
-        import os
         resource_name = 'test_assets.py'
         import pyramid.tests.test_config
         provider = self._makeOne(pyramid.tests.test_config)
-        here = os.path.dirname(os.path.abspath(__file__))
         expected = os.path.join(here, resource_name)
         result = provider.get_resource_filename(None, resource_name)
         self.assertEqual(result, expected)
@@ -214,22 +299,18 @@ class TestOverrideProvider(unittest.TestCase):
     def test_get_resource_stream_override_returns_None(self):
         overrides = DummyOverrides(None)
         self._registerOverrides(overrides)
-        import os
         resource_name = 'test_assets.py'
         import pyramid.tests.test_config
         provider = self._makeOne(pyramid.tests.test_config)
-        here = os.path.dirname(os.path.abspath(__file__))
         with provider.get_resource_stream(None, resource_name) as result:
             _assertBody(result.read(), os.path.join(here, resource_name))
 
     def test_get_resource_string_override_returns_None(self):
         overrides = DummyOverrides(None)
         self._registerOverrides(overrides)
-        import os
         resource_name = 'test_assets.py'
         import pyramid.tests.test_config
         provider = self._makeOne(pyramid.tests.test_config)
-        here = os.path.dirname(os.path.abspath(__file__))
         result = provider.get_resource_string(None, resource_name)
         _assertBody(result, os.path.join(here, resource_name))
 
@@ -378,8 +459,8 @@ class TestPackageOverrides(unittest.TestCase):
         from pyramid.config.assets import DirectoryOverride
         package = DummyPackage('package')
         po = self._makeOne(package)
-        po.overrides= [None]
-        po.insert('foo/', 'package', 'bar/')
+        po.overrides = [None]
+        po.insert('foo/', DummyAssetSource())
         self.assertEqual(len(po.overrides), 2)
         override = po.overrides[0]
         self.assertEqual(override.__class__, DirectoryOverride)
@@ -388,8 +469,8 @@ class TestPackageOverrides(unittest.TestCase):
         from pyramid.config.assets import FileOverride
         package = DummyPackage('package')
         po = self._makeOne(package)
-        po.overrides= [None]
-        po.insert('foo.pt', 'package', 'bar.pt')
+        po.overrides = [None]
+        po.insert('foo.pt', DummyAssetSource())
         self.assertEqual(len(po.overrides), 2)
         override = po.overrides[0]
         self.assertEqual(override.__class__, FileOverride)
@@ -399,132 +480,137 @@ class TestPackageOverrides(unittest.TestCase):
         from pyramid.config.assets import DirectoryOverride
         package = DummyPackage('package')
         po = self._makeOne(package)
-        po.overrides= [None]
-        po.insert('', 'package', 'bar/')
+        po.overrides = [None]
+        source = DummyAssetSource()
+        po.insert('', source)
         self.assertEqual(len(po.overrides), 2)
         override = po.overrides[0]
         self.assertEqual(override.__class__, DirectoryOverride)
 
-    def test_search_path(self):
-        overrides = [ DummyOverride(None), DummyOverride(('package', 'name'))]
+    def test_filtered_sources(self):
+        overrides = [ DummyOverride(None), DummyOverride('foo')]
         package = DummyPackage('package')
         po = self._makeOne(package)
-        po.overrides= overrides
-        self.assertEqual(list(po.search_path('whatever')),
-                         [('package', 'name')])
+        po.overrides = overrides
+        self.assertEqual(list(po.filtered_sources('whatever')), ['foo'])
 
     def test_get_filename(self):
-        import os
-        overrides = [ DummyOverride(None), DummyOverride(
-            ('pyramid.tests.test_config', 'test_assets.py'))]
+        source = DummyAssetSource(filename='foo.pt')
+        overrides = [ DummyOverride(None), DummyOverride((source, ''))]
         package = DummyPackage('package')
         po = self._makeOne(package)
-        po.overrides= overrides
-        here = os.path.dirname(os.path.abspath(__file__))
-        expected = os.path.join(here, 'test_assets.py')
-        self.assertEqual(po.get_filename('whatever'), expected)
+        po.overrides = overrides
+        result = po.get_filename('whatever')
+        self.assertEqual(result, 'foo.pt')
+        self.assertEqual(source.resource_name, '')
 
     def test_get_filename_file_doesnt_exist(self):
-        overrides = [ DummyOverride(None), DummyOverride(
-            ('pyramid.tests.test_config', 'wont_exist'))]
+        source = DummyAssetSource(filename=None)
+        overrides = [DummyOverride(None), DummyOverride((source, 'wont_exist'))]
         package = DummyPackage('package')
         po = self._makeOne(package)
-        po.overrides= overrides
+        po.overrides = overrides
         self.assertEqual(po.get_filename('whatever'), None)
-        
+        self.assertEqual(source.resource_name, 'wont_exist')
+
     def test_get_stream(self):
-        import os
-        overrides = [ DummyOverride(None), DummyOverride(
-            ('pyramid.tests.test_config', 'test_assets.py'))]
+        source = DummyAssetSource(stream='a stream?')
+        overrides = [DummyOverride(None), DummyOverride((source, 'foo.pt'))]
         package = DummyPackage('package')
         po = self._makeOne(package)
-        po.overrides= overrides
-        here = os.path.dirname(os.path.abspath(__file__))
-        with po.get_stream('whatever') as stream:
-            _assertBody(stream.read(), os.path.join(here, 'test_assets.py'))
+        po.overrides = overrides
+        self.assertEqual(po.get_stream('whatever'), 'a stream?')
+        self.assertEqual(source.resource_name, 'foo.pt')
         
     def test_get_stream_file_doesnt_exist(self):
-        overrides = [ DummyOverride(None), DummyOverride(
-            ('pyramid.tests.test_config', 'wont_exist'))]
+        source = DummyAssetSource(stream=None)
+        overrides = [DummyOverride(None), DummyOverride((source, 'wont_exist'))]
         package = DummyPackage('package')
         po = self._makeOne(package)
-        po.overrides= overrides
+        po.overrides = overrides
         self.assertEqual(po.get_stream('whatever'), None)
+        self.assertEqual(source.resource_name, 'wont_exist')
 
     def test_get_string(self):
-        import os
-        overrides = [ DummyOverride(None), DummyOverride(
-            ('pyramid.tests.test_config', 'test_assets.py'))]
+        source = DummyAssetSource(string='a string')
+        overrides = [DummyOverride(None), DummyOverride((source, 'foo.pt'))]
         package = DummyPackage('package')
         po = self._makeOne(package)
-        po.overrides= overrides
-        here = os.path.dirname(os.path.abspath(__file__))
-        _assertBody(po.get_string('whatever'),
-                    os.path.join(here, 'test_assets.py'))
+        po.overrides = overrides
+        self.assertEqual(po.get_string('whatever'), 'a string')
+        self.assertEqual(source.resource_name, 'foo.pt')
         
     def test_get_string_file_doesnt_exist(self):
-        overrides = [ DummyOverride(None), DummyOverride(
-            ('pyramid.tests.test_config', 'wont_exist'))]
+        source = DummyAssetSource(string=None)
+        overrides = [DummyOverride(None), DummyOverride((source, 'wont_exist'))]
         package = DummyPackage('package')
         po = self._makeOne(package)
-        po.overrides= overrides
+        po.overrides = overrides
         self.assertEqual(po.get_string('whatever'), None)
+        self.assertEqual(source.resource_name, 'wont_exist')
 
     def test_has_resource(self):
-        overrides = [ DummyOverride(None), DummyOverride(
-            ('pyramid.tests.test_config', 'test_assets.py'))]
+        source = DummyAssetSource(exists=True)
+        overrides = [DummyOverride(None), DummyOverride((source, 'foo.pt'))]
         package = DummyPackage('package')
         po = self._makeOne(package)
-        po.overrides= overrides
+        po.overrides = overrides
         self.assertEqual(po.has_resource('whatever'), True)
+        self.assertEqual(source.resource_name, 'foo.pt')
 
     def test_has_resource_file_doesnt_exist(self):
-        overrides = [ DummyOverride(None), DummyOverride(
-            ('pyramid.tests.test_config', 'wont_exist'))]
+        source = DummyAssetSource(exists=None)
+        overrides = [DummyOverride(None), DummyOverride((source, 'wont_exist'))]
         package = DummyPackage('package')
         po = self._makeOne(package)
-        po.overrides= overrides
+        po.overrides = overrides
         self.assertEqual(po.has_resource('whatever'), None)
+        self.assertEqual(source.resource_name, 'wont_exist')
 
     def test_isdir_false(self):
-        overrides = [ DummyOverride(
-            ('pyramid.tests.test_config', 'test_assets.py'))]
+        source = DummyAssetSource(isdir=False)
+        overrides = [DummyOverride(None), DummyOverride((source, 'foo.pt'))]
         package = DummyPackage('package')
         po = self._makeOne(package)
-        po.overrides= overrides
+        po.overrides = overrides
         self.assertEqual(po.isdir('whatever'), False)
-        
+        self.assertEqual(source.resource_name, 'foo.pt')
+
     def test_isdir_true(self):
-        overrides = [ DummyOverride(
-            ('pyramid.tests.test_config', 'files'))]
+        source = DummyAssetSource(isdir=True)
+        overrides = [DummyOverride(None), DummyOverride((source, 'foo.pt'))]
         package = DummyPackage('package')
         po = self._makeOne(package)
-        po.overrides= overrides
+        po.overrides = overrides
         self.assertEqual(po.isdir('whatever'), True)
+        self.assertEqual(source.resource_name, 'foo.pt')
 
     def test_isdir_doesnt_exist(self):
-        overrides = [ DummyOverride(None), DummyOverride(
-            ('pyramid.tests.test_config', 'wont_exist'))]
+        source = DummyAssetSource(isdir=None)
+        overrides = [DummyOverride(None), DummyOverride((source, 'wont_exist'))]
         package = DummyPackage('package')
         po = self._makeOne(package)
-        po.overrides= overrides
+        po.overrides = overrides
         self.assertEqual(po.isdir('whatever'), None)
+        self.assertEqual(source.resource_name, 'wont_exist')
 
     def test_listdir(self):
-        overrides = [ DummyOverride(
-            ('pyramid.tests.test_config', 'files'))]
+        source = DummyAssetSource(listdir=True)
+        overrides = [DummyOverride(None), DummyOverride((source, 'foo.pt'))]
         package = DummyPackage('package')
         po = self._makeOne(package)
-        po.overrides= overrides
-        self.assertTrue(po.listdir('whatever'))
+        po.overrides = overrides
+        self.assertEqual(po.listdir('whatever'), True)
+        self.assertEqual(source.resource_name, 'foo.pt')
 
     def test_listdir_doesnt_exist(self):
-        overrides = [ DummyOverride(None), DummyOverride(
-            ('pyramid.tests.test_config', 'wont_exist'))]
+        source = DummyAssetSource(listdir=None)
+        overrides = [DummyOverride(None), DummyOverride((source, 'wont_exist'))]
         package = DummyPackage('package')
         po = self._makeOne(package)
-        po.overrides= overrides
+        po.overrides = overrides
         self.assertEqual(po.listdir('whatever'), None)
+        self.assertEqual(source.resource_name, 'wont_exist')
 
     # PEP 302 __loader__ extensions:  use the "real" __loader__, if present.
     def test_get_data_pkg_has_no___loader__(self):
@@ -570,27 +656,124 @@ class TestPackageOverrides(unittest.TestCase):
 
     def test_get_source_pkg_has___loader__(self):
         package = DummyPackage('package')
-        loader = package.__loader__  = DummyLoader()
+        loader = package.__loader__ = DummyLoader()
         po = self._makeOne(package)
         self.assertEqual(po.get_source('whatever'), 'def foo():\n    pass')
         self.assertEqual(loader._got_source, 'whatever')
 
+class AssetSourceIntegrationTests(object):
+
+    def test_get_filename(self):
+        source = self._makeOne('')
+        self.assertEqual(source.get_filename('test_assets.py'),
+                         os.path.join(here, 'test_assets.py'))
+
+    def test_get_filename_with_prefix(self):
+        source = self._makeOne('test_assets.py')
+        self.assertEqual(source.get_filename(''),
+                         os.path.join(here, 'test_assets.py'))
+
+    def test_get_filename_file_doesnt_exist(self):
+        source = self._makeOne('')
+        self.assertEqual(source.get_filename('wont_exist'), None)
+
+    def test_get_stream(self):
+        source = self._makeOne('')
+        with source.get_stream('test_assets.py') as stream:
+            _assertBody(stream.read(), os.path.join(here, 'test_assets.py'))
+
+    def test_get_stream_with_prefix(self):
+        source = self._makeOne('test_assets.py')
+        with source.get_stream('') as stream:
+            _assertBody(stream.read(), os.path.join(here, 'test_assets.py'))
+
+    def test_get_stream_file_doesnt_exist(self):
+        source = self._makeOne('')
+        self.assertEqual(source.get_stream('wont_exist'), None)
+
+    def test_get_string(self):
+        source = self._makeOne('')
+        _assertBody(source.get_string('test_assets.py'),
+                    os.path.join(here, 'test_assets.py'))
+
+    def test_get_string_with_prefix(self):
+        source = self._makeOne('test_assets.py')
+        _assertBody(source.get_string(''),
+                    os.path.join(here, 'test_assets.py'))
+
+    def test_get_string_file_doesnt_exist(self):
+        source = self._makeOne('')
+        self.assertEqual(source.get_string('wont_exist'), None)
+
+    def test_exists(self):
+        source = self._makeOne('')
+        self.assertEqual(source.exists('test_assets.py'), True)
+
+    def test_exists_with_prefix(self):
+        source = self._makeOne('test_assets.py')
+        self.assertEqual(source.exists(''), True)
+
+    def test_exists_file_doesnt_exist(self):
+        source = self._makeOne('')
+        self.assertEqual(source.exists('wont_exist'), None)
+
+    def test_isdir_false(self):
+        source = self._makeOne('')
+        self.assertEqual(source.isdir('test_assets.py'), False)
+
+    def test_isdir_true(self):
+        source = self._makeOne('')
+        self.assertEqual(source.isdir('files'), True)
+
+    def test_isdir_doesnt_exist(self):
+        source = self._makeOne('')
+        self.assertEqual(source.isdir('wont_exist'), None)
+
+    def test_listdir(self):
+        source = self._makeOne('')
+        self.assertTrue(source.listdir('files'))
+
+    def test_listdir_doesnt_exist(self):
+        source = self._makeOne('')
+        self.assertEqual(source.listdir('wont_exist'), None)
+
+class TestPackageAssetSource(AssetSourceIntegrationTests, unittest.TestCase):
+
+    def _getTargetClass(self):
+        from pyramid.config.assets import PackageAssetSource
+        return PackageAssetSource
+
+    def _makeOne(self, prefix, package='pyramid.tests.test_config'):
+        klass = self._getTargetClass()
+        return klass(package, prefix)
+
+class TestFSAssetSource(AssetSourceIntegrationTests, unittest.TestCase):
+    def _getTargetClass(self):
+        from pyramid.config.assets import FSAssetSource
+        return FSAssetSource
+
+    def _makeOne(self, prefix, base_prefix=here):
+        klass = self._getTargetClass()
+        return klass(os.path.join(base_prefix, prefix))
+
 class TestDirectoryOverride(unittest.TestCase):
     def _getTargetClass(self):
         from pyramid.config.assets import DirectoryOverride
         return DirectoryOverride
 
-    def _makeOne(self, path, package, prefix):
+    def _makeOne(self, path, source):
         klass = self._getTargetClass()
-        return klass(path, package, prefix)
+        return klass(path, source)
 
     def test_it_match(self):
-        o = self._makeOne('foo/', 'package', 'bar/')
+        source = DummyAssetSource()
+        o = self._makeOne('foo/', source)
         result = o('foo/something.pt')
-        self.assertEqual(result, ('package', 'bar/something.pt'))
+        self.assertEqual(result, (source, 'something.pt'))
         
     def test_it_no_match(self):
-        o = self._makeOne('foo/', 'package', 'bar/')
+        source = DummyAssetSource()
+        o = self._makeOne('foo/', source)
         result = o('baz/notfound.pt')
         self.assertEqual(result, None)
 
@@ -599,17 +782,19 @@ class TestFileOverride(unittest.TestCase):
         from pyramid.config.assets import FileOverride
         return FileOverride
 
-    def _makeOne(self, path, package, prefix):
+    def _makeOne(self, path, source):
         klass = self._getTargetClass()
-        return klass(path, package, prefix)
+        return klass(path, source)
 
     def test_it_match(self):
-        o = self._makeOne('foo.pt', 'package', 'bar.pt')
+        source = DummyAssetSource()
+        o = self._makeOne('foo.pt', source)
         result = o('foo.pt')
-        self.assertEqual(result, ('package', 'bar.pt'))
+        self.assertEqual(result, (source, ''))
         
     def test_it_no_match(self):
-        o = self._makeOne('foo.pt', 'package', 'bar.pt')
+        source = DummyAssetSource()
+        o = self._makeOne('foo.pt', source)
         result = o('notfound.pt')
         self.assertEqual(result, None)
 
@@ -634,8 +819,8 @@ class DummyPackageOverrides:
         self.package = package
         self.inserted = []
 
-    def insert(self, path, package, prefix):
-        self.inserted.append((path, package, prefix))
+    def insert(self, path, source):
+        self.inserted.append((path, source))
     
 class DummyPkgResources:
     def __init__(self):
@@ -647,6 +832,34 @@ class DummyPkgResources:
 class DummyPackage:
     def __init__(self, name):
         self.__name__ = name
+
+class DummyAssetSource:
+    def __init__(self, **kw):
+        self.kw = kw
+
+    def get_filename(self, resource_name):
+        self.resource_name = resource_name
+        return self.kw['filename']
+
+    def get_stream(self, resource_name):
+        self.resource_name = resource_name
+        return self.kw['stream']
+
+    def get_string(self, resource_name):
+        self.resource_name = resource_name
+        return self.kw['string']
+
+    def exists(self, resource_name):
+        self.resource_name = resource_name
+        return self.kw['exists']
+
+    def isdir(self, resource_name):
+        self.resource_name = resource_name
+        return self.kw['isdir']
+
+    def listdir(self, resource_name):
+        self.resource_name = resource_name
+        return self.kw['listdir']
  
 class DummyLoader:
     _got_data = _is_package = None
@@ -664,12 +877,10 @@ class DummyLoader:
         return 'def foo():\n    pass'
 
 class DummyUnderOverride:
-    def __call__(self, package, path, override_package, override_prefix,
-                 _info=''):
+    def __call__(self, package, path, source, _info=''):
         self.package = package
         self.path = path
-        self.override_package = override_package
-        self.override_prefix = override_prefix
+        self.source = source
 
 def read_(src):
     with open(src, 'rb') as f: