Implement importlib.abc.SourceLoader and deprecate PyLoader and PyPycLoader.

SourceLoader is a simplification of both PyLoader and PyPycLoader. If one only
wants to use source, then they need to only implement get_data and
get_filename. To also use bytecode -- sourceless loading is not supported --
then two abstract methods -- path_mtime and set_data -- need to be implemented.
Compared to PyLoader and PyPycLoader, there are less abstract methods
introduced and bytecode files become an optimization controlled by the ABC and
hidden from the user (this need came about as PEP 3147 showed that not treating
bytecode as an optimization can cause problems for compatibility).

PyLoader is deprecated in favor of SourceLoader. To be compatible from Python
3.1 onwards, a subclass need only use simple methods for source_path and
is_package. Otherwise conditional subclassing based on whether Python 3.1 or
Python 3.2 is being is the only change. The documentation and docstring for
PyLoader explain what is exactly needed.

PyPycLoader is deprecated also in favor of SourceLoader. Because PEP 3147
shifted bytecode path details so much, there is no foolproof way to provide
backwards-compatibility with SourceLoader. Because of this the class is simply
deprecated and users should move to SourceLoader (and optionally PyLoader for
Python 3.1). This does lead to a loss of support for sourceless loading
unfortunately.

At some point before Python 3.2 is released, SourceLoader will be moved over to
importlib._bootstrap so that the core code of importlib relies on the new code
instead of the old PyPycLoader code. This commit is being done now so that
there is no issue in having the API in Python 3.1a1.

1 files changed, 394 insertions, 6 deletions

diff --git a/Lib/importlib/test/source/test_abc_loader.py b/Lib/importlib/test/source/test_abc_loader.py
index 8c69cfd..69cc9fd 100644
--- a/Lib/importlib/test/source/test_abc_loader.py
+++ b/Lib/importlib/test/source/test_abc_loader.py
@@ -1,14 +1,67 @@
 import importlib
 from importlib import abc
+
 from .. import abc as testing_abc
 from .. import util
 from . import util as source_util
+
 import imp
+import inspect
 import marshal
 import os
 import sys
 import types
 import unittest
+import warnings
+
+
+class SourceOnlyLoaderMock(abc.SourceLoader):
+
+    # Globals that should be defined for all modules.
+    source = (b"_ = '::'.join([__name__, __file__, __cached__, __package__, "
+              b"repr(__loader__)])")
+
+    def __init__(self, path):
+        self.path = path
+
+    def get_data(self, path):
+        assert self.path == path
+        return self.source
+
+    def get_filename(self, fullname):
+        return self.path
+
+
+class SourceLoaderMock(SourceOnlyLoaderMock):
+
+    source_mtime = 1
+
+    def __init__(self, path, magic=imp.get_magic()):
+        super().__init__(path)
+        self.bytecode_path = imp.cache_from_source(self.path)
+        data = bytearray(magic)
+        data.extend(marshal._w_long(self.source_mtime))
+        code_object = compile(self.source, self.path, 'exec',
+                                dont_inherit=True)
+        data.extend(marshal.dumps(code_object))
+        self.bytecode = bytes(data)
+        self.written = {}
+
+    def get_data(self, path):
+        if path == self.path:
+            return super().get_data(path)
+        elif path == self.bytecode_path:
+            return self.bytecode
+        else:
+            raise IOError
+
+    def path_mtime(self, path):
+        assert path == self.path
+        return self.source_mtime
+
+    def set_data(self, path, data):
+        self.written[path] = bytes(data)
+        return path == self.bytecode_path
 
 
 class PyLoaderMock(abc.PyLoader):
@@ -33,17 +86,42 @@ class PyLoaderMock(abc.PyLoader):
         return self.source
 
     def is_package(self, name):
+        filename = os.path.basename(self.get_filename(name))
+        return os.path.splitext(filename)[0] == '__init__'
+
+    def source_path(self, name):
         try:
-            return '__init__' in self.module_paths[name]
+            return self.module_paths[name]
         except KeyError:
             raise ImportError
 
-    def source_path(self, name):
+    def get_filename(self, name):
+        """Silence deprecation warning."""
+        with warnings.catch_warnings(record=True) as w:
+            warnings.simplefilter("always")
+            path = super().get_filename(name)
+            assert len(w) == 1
+            assert issubclass(w[0].category, PendingDeprecationWarning)
+            return path
+
+
+class PyLoaderCompatMock(PyLoaderMock):
+
+    """Mock that matches what is suggested to have a loader that is compatible
+    from Python 3.1 onwards."""
+
+    def get_filename(self, fullname):
         try:
-            return self.module_paths[name]
+            return self.module_paths[fullname]
         except KeyError:
             raise ImportError
 
+    def source_path(self, fullname):
+        try:
+            return self.get_filename(fullname)
+        except ImportError:
+            return None
+
 
 class PyPycLoaderMock(abc.PyPycLoader, PyLoaderMock):
 
@@ -114,6 +192,13 @@ class PyPycLoaderMock(abc.PyPycLoader, PyLoaderMock):
         except TypeError:
             return '__init__' in self.bytecode_to_path[name]
 
+    def get_code(self, name):
+        with warnings.catch_warnings(record=True) as w:
+            warnings.simplefilter("always")
+            code_object = super().get_code(name)
+            assert len(w) == 1
+            assert issubclass(w[0].category, PendingDeprecationWarning)
+            return code_object
 
 class PyLoaderTests(testing_abc.LoaderTests):
 
@@ -200,6 +285,14 @@ class PyLoaderTests(testing_abc.LoaderTests):
         return mock
 
 
+class PyLoaderCompatTests(PyLoaderTests):
+
+    """Test that the suggested code to make a loader that is compatible from
+    Python 3.1 forward works."""
+
+    mocker = PyLoaderCompatMock
+
+
 class PyLoaderInterfaceTests(unittest.TestCase):
 
     """Tests for importlib.abc.PyLoader to make sure that when source_path()
@@ -413,7 +506,7 @@ class BadBytecodeFailureTests(unittest.TestCase):
     def test_bad_bytecode(self):
         # Malformed code object bytecode should lead to a ValueError.
         name = 'mod'
-        bc = {name: {'path': os.path.join('path', 'to', 'mod'), 'bc': b'XXX'}}
+        bc = {name: {'path': os.path.join('path', 'to', 'mod'), 'bc': b'NNN'}}
         mock = PyPycLoaderMock({name: None}, bc)
         with util.uncache(name), self.assertRaises(ValueError):
             mock.load_module(name)
@@ -465,12 +558,307 @@ class MissingPathsTests(unittest.TestCase):
             mock.load_module(name)
 
 
+class SourceLoaderTestHarness(unittest.TestCase):
+
+    def setUp(self, *, is_package=True, **kwargs):
+        self.package = 'pkg'
+        if is_package:
+            self.path = os.path.join(self.package, '__init__.py')
+            self.name = self.package
+        else:
+            module_name = 'mod'
+            self.path = os.path.join(self.package, '.'.join(['mod', 'py']))
+            self.name = '.'.join([self.package, module_name])
+        self.cached = imp.cache_from_source(self.path)
+        self.loader = self.loader_mock(self.path, **kwargs)
+
+    def verify_module(self, module):
+        self.assertEqual(module.__name__, self.name)
+        self.assertEqual(module.__file__, self.path)
+        self.assertEqual(module.__cached__, self.cached)
+        self.assertEqual(module.__package__, self.package)
+        self.assertEqual(module.__loader__, self.loader)
+        values = module._.split('::')
+        self.assertEqual(values[0], self.name)
+        self.assertEqual(values[1], self.path)
+        self.assertEqual(values[2], self.cached)
+        self.assertEqual(values[3], self.package)
+        self.assertEqual(values[4], repr(self.loader))
+
+    def verify_code(self, code_object):
+        module = imp.new_module(self.name)
+        module.__file__ = self.path
+        module.__cached__ = self.cached
+        module.__package__ = self.package
+        module.__loader__ = self.loader
+        module.__path__ = []
+        exec(code_object, module.__dict__)
+        self.verify_module(module)
+
+
+class SourceOnlyLoaderTests(SourceLoaderTestHarness):
+
+    """Test importlib.abc.SourceLoader for source-only loading.
+
+    Reload testing is subsumed by the tests for
+    importlib.util.module_for_loader.
+
+    """
+
+    loader_mock = SourceOnlyLoaderMock
+
+    def test_get_source(self):
+        # Verify the source code is returned as a string.
+        # If an IOError is raised by get_data then raise ImportError.
+        expected_source = self.loader.source.decode('utf-8')
+        self.assertEqual(self.loader.get_source(self.name), expected_source)
+        def raise_IOError(path):
+            raise IOError
+        self.loader.get_data = raise_IOError
+        with self.assertRaises(ImportError):
+            self.loader.get_source(self.name)
+
+    def test_is_package(self):
+        # Properly detect when loading a package.
+        self.setUp(is_package=True)
+        self.assertTrue(self.loader.is_package(self.name))
+        self.setUp(is_package=False)
+        self.assertFalse(self.loader.is_package(self.name))
+
+    def test_get_code(self):
+        # Verify the code object is created.
+        code_object = self.loader.get_code(self.name)
+        self.verify_code(code_object)
+
+    def test_load_module(self):
+        # Loading a module should set __name__, __loader__, __package__,
+        # __path__ (for packages), __file__, and __cached__.
+        # The module should also be put into sys.modules.
+        with util.uncache(self.name):
+            module = self.loader.load_module(self.name)
+            self.verify_module(module)
+            self.assertEqual(module.__path__, [os.path.dirname(self.path)])
+            self.assertTrue(self.name in sys.modules)
+
+    def test_package_settings(self):
+        # __package__ needs to be set, while __path__ is set on if the module
+        # is a package.
+        # Testing the values for a package are covered by test_load_module.
+        self.setUp(is_package=False)
+        with util.uncache(self.name):
+            module = self.loader.load_module(self.name)
+            self.verify_module(module)
+            self.assertTrue(not hasattr(module, '__path__'))
+
+    def test_get_source_encoding(self):
+        # Source is considered encoded in UTF-8 by default unless otherwise
+        # specified by an encoding line.
+        source = "_ = 'ü'"
+        self.loader.source = source.encode('utf-8')
+        returned_source = self.loader.get_source(self.name)
+        self.assertEqual(returned_source, source)
+        source = "# coding: latin-1\n_ = ü"
+        self.loader.source = source.encode('latin-1')
+        returned_source = self.loader.get_source(self.name)
+        self.assertEqual(returned_source, source)
+
+
+@unittest.skipIf(sys.dont_write_bytecode, "sys.dont_write_bytecode is true")
+class SourceLoaderBytecodeTests(SourceLoaderTestHarness):
+
+    """Test importlib.abc.SourceLoader's use of bytecode.
+
+    Source-only testing handled by SourceOnlyLoaderTests.
+
+    """
+
+    loader_mock = SourceLoaderMock
+
+    def verify_code(self, code_object, *, bytecode_written=False):
+        super().verify_code(code_object)
+        if bytecode_written:
+            self.assertIn(self.cached, self.loader.written)
+            data = bytearray(imp.get_magic())
+            data.extend(marshal._w_long(self.loader.source_mtime))
+            data.extend(marshal.dumps(code_object))
+            self.assertEqual(self.loader.written[self.cached], bytes(data))
+
+    def test_code_with_everything(self):
+        # When everything should work.
+        code_object = self.loader.get_code(self.name)
+        self.verify_code(code_object)
+
+    def test_no_bytecode(self):
+        # If no bytecode exists then move on to the source.
+        self.loader.bytecode_path = "<does not exist>"
+        # Sanity check
+        with self.assertRaises(IOError):
+            bytecode_path = imp.cache_from_source(self.path)
+            self.loader.get_data(bytecode_path)
+        code_object = self.loader.get_code(self.name)
+        self.verify_code(code_object, bytecode_written=True)
+
+    def test_code_bad_timestamp(self):
+        # Bytecode is only used when the timestamp matches the source EXACTLY.
+        for source_mtime in (0, 2):
+            assert source_mtime != self.loader.source_mtime
+            original = self.loader.source_mtime
+            self.loader.source_mtime = source_mtime
+            # If bytecode is used then EOFError would be raised by marshal.
+            self.loader.bytecode = self.loader.bytecode[8:]
+            code_object = self.loader.get_code(self.name)
+            self.verify_code(code_object, bytecode_written=True)
+            self.loader.source_mtime = original
+
+    def test_code_bad_magic(self):
+        # Skip over bytecode with a bad magic number.
+        self.setUp(magic=b'0000')
+        # If bytecode is used then EOFError would be raised by marshal.
+        self.loader.bytecode = self.loader.bytecode[8:]
+        code_object = self.loader.get_code(self.name)
+        self.verify_code(code_object, bytecode_written=True)
+
+    def test_dont_write_bytecode(self):
+        # Bytecode is not written if sys.dont_write_bytecode is true.
+        # Can assume it is false already thanks to the skipIf class decorator.
+        try:
+            sys.dont_write_bytecode = True
+            self.loader.bytecode_path = "<does not exist>"
+            code_object = self.loader.get_code(self.name)
+            self.assertNotIn(self.cached, self.loader.written)
+        finally:
+            sys.dont_write_bytecode = False
+
+    def test_no_set_data(self):
+        # If set_data is not defined, one can still read bytecode.
+        self.setUp(magic=b'0000')
+        original_set_data = self.loader.__class__.set_data
+        try:
+            del self.loader.__class__.set_data
+            code_object = self.loader.get_code(self.name)
+            self.verify_code(code_object)
+        finally:
+            self.loader.__class__.set_data = original_set_data
+
+    def test_set_data_raises_exceptions(self):
+        # Raising NotImplementedError or IOError is okay for set_data.
+        def raise_exception(exc):
+            def closure(*args, **kwargs):
+                raise exc
+            return closure
+
+        self.setUp(magic=b'0000')
+        for exc in (NotImplementedError, IOError):
+            self.loader.set_data = raise_exception(exc)
+            code_object = self.loader.get_code(self.name)
+            self.verify_code(code_object)
+
+class AbstractMethodImplTests(unittest.TestCase):
+
+    """Test the concrete abstractmethod implementations."""
+
+    class Loader(abc.Loader):
+        def load_module(self, fullname):
+            super().load_module(fullname)
+
+    class Finder(abc.Finder):
+        def find_module(self, _):
+            super().find_module(_)
+
+    class ResourceLoader(Loader, abc.ResourceLoader):
+        def get_data(self, _):
+            super().get_data(_)
+
+    class InspectLoader(Loader, abc.InspectLoader):
+        def is_package(self, _):
+            super().is_package(_)
+
+        def get_code(self, _):
+            super().get_code(_)
+
+        def get_source(self, _):
+            super().get_source(_)
+
+    class ExecutionLoader(InspectLoader, abc.ExecutionLoader):
+        def get_filename(self, _):
+            super().get_filename(_)
+
+    class SourceLoader(ResourceLoader, ExecutionLoader, abc.SourceLoader):
+        pass
+
+    class PyLoader(ResourceLoader, InspectLoader, abc.PyLoader):
+        def source_path(self, _):
+            super().source_path(_)
+
+    class PyPycLoader(PyLoader, abc.PyPycLoader):
+        def bytecode_path(self, _):
+            super().bytecode_path(_)
+
+        def source_mtime(self, _):
+            super().source_mtime(_)
+
+        def write_bytecode(self, _, _2):
+            super().write_bytecode(_, _2)
+
+    def raises_NotImplementedError(self, ins, *args):
+        for method_name in args:
+            method = getattr(ins, method_name)
+            arg_count = len(inspect.getfullargspec(method)[0]) - 1
+            args = [''] * arg_count
+            try:
+                method(*args)
+            except NotImplementedError:
+                pass
+            else:
+                msg = "{}.{} did not raise NotImplementedError"
+                self.fail(msg.format(ins.__class__.__name__, method_name))
+
+    def test_Loader(self):
+        self.raises_NotImplementedError(self.Loader(), 'load_module')
+
+    def test_Finder(self):
+        self.raises_NotImplementedError(self.Finder(), 'find_module')
+
+    def test_ResourceLoader(self):
+        self.raises_NotImplementedError(self.ResourceLoader(), 'load_module',
+                                        'get_data')
+
+    def test_InspectLoader(self):
+        self.raises_NotImplementedError(self.InspectLoader(), 'load_module',
+                                        'is_package', 'get_code', 'get_source')
+
+    def test_ExecutionLoader(self):
+        self.raises_NotImplementedError(self.ExecutionLoader(), 'load_module',
+                                        'is_package', 'get_code', 'get_source',
+                                        'get_filename')
+
+    def test_SourceLoader(self):
+        ins = self.SourceLoader()
+        # Required abstractmethods.
+        self.raises_NotImplementedError(ins, 'get_filename', 'get_data')
+        # Optional abstractmethods.
+        self.raises_NotImplementedError(ins,'path_mtime', 'set_data')
+
+    def test_PyLoader(self):
+        self.raises_NotImplementedError(self.PyLoader(), 'source_path',
+                                        'get_data', 'is_package')
+
+    def test_PyPycLoader(self):
+        self.raises_NotImplementedError(self.PyPycLoader(), 'source_path',
+                                        'source_mtime', 'bytecode_path',
+                                        'write_bytecode')
+
+
 def test_main():
     from test.support import run_unittest
-    run_unittest(PyLoaderTests, PyLoaderInterfaceTests, PyLoaderGetSourceTests,
+    run_unittest(PyLoaderTests, PyLoaderCompatTests,
+                    PyLoaderInterfaceTests, PyLoaderGetSourceTests,
                     PyPycLoaderTests, PyPycLoaderInterfaceTests,
                     SkipWritingBytecodeTests, RegeneratedBytecodeTests,
-                    BadBytecodeFailureTests, MissingPathsTests)
+                    BadBytecodeFailureTests, MissingPathsTests,
+                    SourceOnlyLoaderTests,
+                    SourceLoaderBytecodeTests,
+                    AbstractMethodImplTests)
 
 
 if __name__ == '__main__':