Use the ResourceReader API

importlib_resources/__init__.py

@@ -47,27 +47,31 @@ def open(package: Package, file_name: FileName) -> BinaryIO:
     """Return a file-like object opened for binary-reading of the resource."""
     file_name = _normalize_path(file_name)
     package = _get_package(package)
-    # Using pathlib doesn't work well here due to the lack of 'strict' argument
-    # for pathlib.Path.resolve() prior to Python 3.6.
-    absolute_package_path = os.path.abspath(package.__spec__.origin)
-    package_path = os.path.dirname(absolute_package_path)
-    full_path = os.path.join(package_path, file_name)
     try:
-        return builtins.open(full_path, 'rb')
-    except IOError:
-        # Just assume the loader is a resource loader; all the relevant
-        # importlib.machinery loaders are and an AttributeError for get_data()
-        # will make it clear what is needed from the loader.
-        loader = typing.cast(importlib.abc.ResourceLoader,
-                             package.__spec__.loader)
+        return package.__spec__.loader.open_resource(file_name)
+    except AttributeError:
+        # Using pathlib doesn't work well here due to the lack of 'strict'
+        # argument for pathlib.Path.resolve() prior to Python 3.6.
+        absolute_package_path = os.path.abspath(package.__spec__.origin)
+        package_path = os.path.dirname(absolute_package_path)
+        full_path = os.path.join(package_path, file_name)
         try:
-            data = loader.get_data(full_path)
+            return builtins.open(full_path, 'rb')
         except IOError:
-            package_name = package.__spec__.name
-            message = '{!r} resource not found in {!r}'.format(file_name, package_name)
-            raise FileNotFoundError(message)
-        else:
-            return io.BytesIO(data)
+            # Just assume the loader is a resource loader; all the relevant
+            # importlib.machinery loaders are and an AttributeError for
+            # get_data() will make it clear what is needed from the loader.
+            loader = typing.cast(importlib.abc.ResourceLoader,
+                                package.__spec__.loader)
+            try:
+                data = loader.get_data(full_path)
+            except IOError:
+                package_name = package.__spec__.name
+                message = '{!r} resource not found in {!r}'.format(file_name,
+                                                                   package_name)
+                raise FileNotFoundError(message)
+            else:
+                return io.BytesIO(data)
 
 
 def read(package: Package, file_name: FileName, encoding: str = 'utf-8',
@@ -98,25 +102,28 @@ def path(package: Package, file_name: FileName) -> Iterator[pathlib.Path]:
     raised if the file was deleted prior to the context manager
     exiting).
     """
-    normalized_path = _normalize_path(file_name)
+    file_name = _normalize_path(file_name)
     package = _get_package(package)
-    package_directory = pathlib.Path(package.__spec__.origin).parent
-    file_path = package_directory / normalized_path
-    if file_path.exists():
-        yield file_path
-    else:
-        with open(package, normalized_path) as file:
-            data = file.read()
-        # Not using tempfile.NamedTemporaryFile as it leads to deeper 'try'
-        # blocks due to the need to close the temporary file to work on
-        # Windows properly.
-        fd, raw_path = tempfile.mkstemp()
-        try:
-            os.write(fd, data)
-            os.close(fd)
-            yield pathlib.Path(raw_path)
-        finally:
+    try:
+        yield pathlib.Path(package.__spec__.loader.resource_path(file_name))
+    except (AttributeError, FileNotFoundError):
+        package_directory = pathlib.Path(package.__spec__.origin).parent
+        file_path = package_directory / file_name
+        if file_path.exists():
+            yield file_path
+        else:
+            with open(package, file_name) as file:
+                data = file.read()
+            # Not using tempfile.NamedTemporaryFile as it leads to deeper 'try'
+            # blocks due to the need to close the temporary file to work on
+            # Windows properly.
+            fd, raw_path = tempfile.mkstemp()
             try:
-                os.remove(raw_path)
-            except FileNotFoundError:
-                pass
+                os.write(fd, data)
+                os.close(fd)
+                yield pathlib.Path(raw_path)
+            finally:
+                try:
+                    os.remove(raw_path)
+                except FileNotFoundError:
+                    pass

importlib_resources/tests/util.py

@@ -1,12 +1,38 @@
 import abc
 import importlib
+import importlib.machinery
+import importlib.util
+import io
 import pathlib
 import sys
 import unittest
 
+from .. import abc as resources_abc
 from . import data
 
 
+def create_package(*, file, path):
+    class Reader(resources_abc.ResourceReader):
+        def open_resource(self, path):
+            self._path = path
+            if isinstance(file, Exception):
+                raise file
+            else:
+                return file
+
+        def resource_path(self, path_):
+            self._path = path_
+            if isinstance(path, Exception):
+                raise path
+            else:
+                return path
+
+    spec = importlib.machinery.ModuleSpec('testingpackage', Reader(),
+                                          origin='does-not-exist',
+                                          is_package=True)
+    return importlib.util.module_from_spec(spec)
+
+
 class CommonTests(abc.ABC):
 
     @abc.abstractmethod
@@ -54,6 +80,25 @@ def test_non_package(self):
         with self.assertRaises(TypeError):
             self.execute(__spec__.name, 'utf-8.file')
 
+    def test_resource_opener(self):
+        data = io.BytesIO(b'Hello, world!')
+        package = create_package(file=data, path=FileNotFoundError())
+        self.execute(package, 'utf-8.file')
+        self.assertEqual(package.__spec__.loader._path, 'utf-8.file')
+
+    def test_resource_path(self):
+        data = io.BytesIO(b'Hello, world!')
+        path = __file__
+        package = create_package(file=data, path=path)
+        self.execute(package, 'utf-8.file')
+        self.assertEqual(package.__spec__.loader._path, 'utf-8.file')
+
+    def test_useless_loader(self):
+        package = create_package(file=FileNotFoundError(),
+                                 path=FileNotFoundError())
+        with self.assertRaises(FileNotFoundError):
+            self.execute(package, 'utf-8.file')
+
 
 class ZipSetup: