bpo-32248: Implement importlib.abc.ResourceReader (GH-4892)

2 files changed, 77 insertions, 0 deletions

diff --git a/Lib/importlib/abc.py b/Lib/importlib/abc.py
index d7cadf2..b772db3 100644
--- a/Lib/importlib/abc.py
+++ b/Lib/importlib/abc.py
@@ -340,3 +340,41 @@ class SourceLoader(_bootstrap_external.SourceLoader, ResourceLoader, ExecutionLo
         """
 
 _register(SourceLoader, machinery.SourceFileLoader)
+
+
+class ResourceReader(Loader):
+
+    """Abstract base class for loaders to provide resource reading support."""
+
+    @abc.abstractmethod
+    def open_resource(self, resource):
+        """Return an opened, file-like object for binary reading.
+
+        The 'resource' argument is expected to represent only a file name
+        and thus not contain any subdirectory components.
+
+        If the resource cannot be found, FileNotFoundError is raised.
+        """
+        raise FileNotFoundError
+
+    @abc.abstractmethod
+    def resource_path(self, resource):
+        """Return the file system path to the specified resource.
+
+        The 'resource' argument is expected to represent only a file name
+        and thus not contain any subdirectory components.
+
+        If the resource does not exist on the file system, raise
+        FileNotFoundError.
+        """
+        raise FileNotFoundError
+
+    @abc.abstractmethod
+    def is_resource(self, name):
+        """Return True if the named 'name' is consider a resource."""
+        raise FileNotFoundError
+
+    @abc.abstractmethod
+    def contents(self):
+        """Return an iterator of strings over the contents of the package."""
+        return iter([])
diff --git a/Lib/test/test_importlib/test_abc.py b/Lib/test/test_importlib/test_abc.py
index 4ba28c6..f1e1db3 100644
--- a/Lib/test/test_importlib/test_abc.py
+++ b/Lib/test/test_importlib/test_abc.py
@@ -305,6 +305,45 @@ class ExecutionLoaderDefaultsTests(ABCTestHarness):
  ) = test_util.test_both(InspectLoaderDefaultsTests)
 
 
+class ResourceReader:
+
+    def open_resource(self, *args, **kwargs):
+        return super().open_resource(*args, **kwargs)
+
+    def resource_path(self, *args, **kwargs):
+        return super().resource_path(*args, **kwargs)
+
+    def is_resource(self, *args, **kwargs):
+        return super().is_resource(*args, **kwargs)
+
+    def contents(self, *args, **kwargs):
+        return super().contents(*args, **kwargs)
+
+
+class ResourceReaderDefaultsTests(ABCTestHarness):
+
+    SPLIT = make_abc_subclasses(ResourceReader)
+
+    def test_open_resource(self):
+        with self.assertRaises(FileNotFoundError):
+            self.ins.open_resource('dummy_file')
+
+    def test_resource_path(self):
+        with self.assertRaises(FileNotFoundError):
+            self.ins.resource_path('dummy_file')
+
+    def test_is_resource(self):
+        with self.assertRaises(FileNotFoundError):
+            self.ins.is_resource('dummy_file')
+
+    def test_contents(self):
+        self.assertEqual([], list(self.ins.contents()))
+
+(Frozen_RRDefaultTests,
+ Source_RRDefaultsTests
+ ) = test_util.test_both(ResourceReaderDefaultsTests)
+
+
 ##### MetaPathFinder concrete methods ##########################################
 class MetaPathFinderFindModuleTests: