import io
import marshal
import os
import sys
from test.support import import_helper
import types
import unittest
from unittest import mock
import warnings

from test.test_importlib import util as test_util

init = test_util.import_importlib('importlib')
abc = test_util.import_importlib('importlib.abc')
machinery = test_util.import_importlib('importlib.machinery')
util = test_util.import_importlib('importlib.util')


##### Inheritance ##############################################################
class InheritanceTests:

    """Test that the specified class is a subclass/superclass of the expected
    classes."""

    subclasses = []
    superclasses = []

    def setUp(self):
        self.superclasses = [getattr(self.abc, class_name)
                             for class_name in self.superclass_names]
        if hasattr(self, 'subclass_names'):
            # Because test.support.import_fresh_module() creates a new
            # importlib._bootstrap per module, inheritance checks fail when
            # checking across module boundaries (i.e. the _bootstrap in abc is
            # not the same as the one in machinery). That means stealing one of
            # the modules from the other to make sure the same instance is used.
            machinery = self.abc.machinery
            self.subclasses = [getattr(machinery, class_name)
                               for class_name in self.subclass_names]
        assert self.subclasses or self.superclasses, self.__class__
        self.__test = getattr(self.abc, self._NAME)

    def test_subclasses(self):
        # Test that the expected subclasses inherit.
        for subclass in self.subclasses:
            self.assertIsSubclass(subclass, self.__test)

    def test_superclasses(self):
        # Test that the class inherits from the expected superclasses.
        for superclass in self.superclasses:
            self.assertIsSubclass(self.__test, superclass)


class MetaPathFinder(InheritanceTests):
    superclass_names = []
    subclass_names = ['BuiltinImporter', 'FrozenImporter', 'PathFinder',
                      'WindowsRegistryFinder']


(Frozen_MetaPathFinderInheritanceTests,
 Source_MetaPathFinderInheritanceTests
 ) = test_util.test_both(MetaPathFinder, abc=abc)


class PathEntryFinder(InheritanceTests):
    superclass_names = []
    subclass_names = ['FileFinder']


(Frozen_PathEntryFinderInheritanceTests,
 Source_PathEntryFinderInheritanceTests
 ) = test_util.test_both(PathEntryFinder, abc=abc)


class ResourceLoader(InheritanceTests):
    superclass_names = ['Loader']


(Frozen_ResourceLoaderInheritanceTests,
 Source_ResourceLoaderInheritanceTests
 ) = test_util.test_both(ResourceLoader, abc=abc)


class InspectLoader(InheritanceTests):
    superclass_names = ['Loader']
    subclass_names = ['BuiltinImporter', 'FrozenImporter', 'ExtensionFileLoader']


(Frozen_InspectLoaderInheritanceTests,
 Source_InspectLoaderInheritanceTests
 ) = test_util.test_both(InspectLoader, abc=abc)


class ExecutionLoader(InheritanceTests):
    superclass_names = ['InspectLoader']
    subclass_names = ['ExtensionFileLoader']


(Frozen_ExecutionLoaderInheritanceTests,
 Source_ExecutionLoaderInheritanceTests
 ) = test_util.test_both(ExecutionLoader, abc=abc)


class FileLoader(InheritanceTests):
    superclass_names = ['ResourceLoader', 'ExecutionLoader']
    subclass_names = ['SourceFileLoader', 'SourcelessFileLoader']


(Frozen_FileLoaderInheritanceTests,
 Source_FileLoaderInheritanceTests
 ) = test_util.test_both(FileLoader, abc=abc)


class SourceLoader(InheritanceTests):
    superclass_names = ['ResourceLoader', 'ExecutionLoader']
    subclass_names = ['SourceFileLoader']


(Frozen_SourceLoaderInheritanceTests,
 Source_SourceLoaderInheritanceTests
 ) = test_util.test_both(SourceLoader, abc=abc)


##### Default return values ####################################################

def make_abc_subclasses(base_class, name=None, inst=False, **kwargs):
    if name is None:
        name = base_class.__name__
    base = {kind: getattr(splitabc, name)
            for kind, splitabc in abc.items()}
    return {cls._KIND: cls() if inst else cls
            for cls in test_util.split_frozen(base_class, base, **kwargs)}


class ABCTestHarness:

    @property
    def ins(self):
        # Lazily set ins on the class.
        cls = self.SPLIT[self._KIND]
        ins = cls()
        self.__class__.ins = ins
        return ins


class MetaPathFinder:

    pass


class MetaPathFinderDefaultsTests(ABCTestHarness):

    SPLIT = make_abc_subclasses(MetaPathFinder)

    def test_invalidate_caches(self):
        # Calling the method is a no-op.
        self.ins.invalidate_caches()


(Frozen_MPFDefaultTests,
 Source_MPFDefaultTests
 ) = test_util.test_both(MetaPathFinderDefaultsTests)


class PathEntryFinder:

    pass


class PathEntryFinderDefaultsTests(ABCTestHarness):

    SPLIT = make_abc_subclasses(PathEntryFinder)

    def test_invalidate_caches(self):
        # Should be a no-op.
        self.ins.invalidate_caches()


(Frozen_PEFDefaultTests,
 Source_PEFDefaultTests
 ) = test_util.test_both(PathEntryFinderDefaultsTests)


class Loader:

    pass


class LoaderDefaultsTests(ABCTestHarness):

    SPLIT = make_abc_subclasses(Loader)

    def test_create_module(self):
        spec = 'a spec'
        self.assertIsNone(self.ins.create_module(spec))

    def test_module_repr(self):
        mod = types.ModuleType('blah')
        with warnings.catch_warnings():
            warnings.simplefilter("ignore", DeprecationWarning)
            original_repr = repr(mod)
            mod.__loader__ = self.ins
            # Should still return a proper repr.
            self.assertTrue(repr(mod))


(Frozen_LDefaultTests,
 SourceLDefaultTests
 ) = test_util.test_both(LoaderDefaultsTests)


class ResourceLoader(Loader):

    def get_data(self, path):
        return super().get_data(path)


class ResourceLoaderDefaultsTests(ABCTestHarness):

    SPLIT = make_abc_subclasses(ResourceLoader)

    def test_get_data(self):
        with self.assertRaises(IOError):
            self.ins.get_data('/some/path')


(Frozen_RLDefaultTests,
 Source_RLDefaultTests
 ) = test_util.test_both(ResourceLoaderDefaultsTests)


class InspectLoader(Loader):

    def is_package(self, fullname):
        return super().is_package(fullname)

    def get_source(self, fullname):
        return super().get_source(fullname)


SPLIT_IL = make_abc_subclasses(InspectLoader)


class InspectLoaderDefaultsTests(ABCTestHarness):

    SPLIT = SPLIT_IL

    def test_is_package(self):
        with self.assertRaises(ImportError):
            self.ins.is_package('blah')

    def test_get_source(self):
        with self.assertRaises(ImportError):
            self.ins.get_source('blah')


(Frozen_ILDefaultTests,
 Source_ILDefaultTests
 ) = test_util.test_both(InspectLoaderDefaultsTests)


class ExecutionLoader(InspectLoader):

    def get_filename(self, fullname):
        return super().get_filename(fullname)


SPLIT_EL = make_abc_subclasses(ExecutionLoader)


class ExecutionLoaderDefaultsTests(ABCTestHarness):

    SPLIT = SPLIT_EL

    def test_get_filename(self):
        with self.assertRaises(ImportError):
            self.ins.get_filename('blah')


(Frozen_ELDefaultTests,
 Source_ELDefaultsTests
 ) = 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)


##### MetaPathFinder concrete methods ##########################################
class MetaPathFinderFindModuleTests:

    @classmethod
    def finder(cls, spec):
        class MetaPathSpecFinder(cls.abc.MetaPathFinder):

            def find_spec(self, fullname, path, target=None):
                self.called_for = fullname, path
                return spec

        return MetaPathSpecFinder()

    def test_find_spec_with_explicit_target(self):
        loader = object()
        spec = self.util.spec_from_loader('blah', loader)
        finder = self.finder(spec)
        found = finder.find_spec('blah', 'blah', None)
        self.assertEqual(found, spec)

    def test_no_spec(self):
        finder = self.finder(None)
        path = ['a', 'b', 'c']
        name = 'blah'
        found = finder.find_spec(name, path, None)
        self.assertIsNone(found)
        self.assertEqual(name, finder.called_for[0])
        self.assertEqual(path, finder.called_for[1])

    def test_spec(self):
        loader = object()
        spec = self.util.spec_from_loader('blah', loader)
        finder = self.finder(spec)
        found = finder.find_spec('blah', None)
        self.assertIs(found, spec)


(Frozen_MPFFindModuleTests,
 Source_MPFFindModuleTests
 ) = test_util.test_both(MetaPathFinderFindModuleTests, abc=abc, util=util)


##### Loader concrete methods ##################################################
class LoaderLoadModuleTests:

    def loader(self):
        class SpecLoader(self.abc.Loader):
            found = None
            def exec_module(self, module):
                self.found = module

            def is_package(self, fullname):
                """Force some non-default module state to be set."""
                return True

        return SpecLoader()


(Frozen_LoaderLoadModuleTests,
 Source_LoaderLoadModuleTests
 ) = test_util.test_both(LoaderLoadModuleTests, abc=abc, util=util)


##### InspectLoader concrete methods ###########################################
class InspectLoaderSourceToCodeTests:

    def source_to_module(self, data, path=None):
        """Help with source_to_code() tests."""
        module = types.ModuleType('blah')
        loader = self.InspectLoaderSubclass()
        if path is None:
            code = loader.source_to_code(data)
        else:
            code = loader.source_to_code(data, path)
        exec(code, module.__dict__)
        return module

    def test_source_to_code_source(self):
        # Since compile() can handle strings, so should source_to_code().
        source = 'attr = 42'
        module = self.source_to_module(source)
        self.assertHasAttr(module, 'attr')
        self.assertEqual(module.attr, 42)

    def test_source_to_code_bytes(self):
        # Since compile() can handle bytes, so should source_to_code().
        source = b'attr = 42'
        module = self.source_to_module(source)
        self.assertHasAttr(module, 'attr')
        self.assertEqual(module.attr, 42)

    def test_source_to_code_path(self):
        # Specifying a path should set it for the code object.
        path = 'path/to/somewhere'
        loader = self.InspectLoaderSubclass()
        code = loader.source_to_code('', path)
        self.assertEqual(code.co_filename, path)

    def test_source_to_code_no_path(self):
        # Not setting a path should still work and be set to <string> since that
        # is a pre-existing practice as a default to compile().
        loader = self.InspectLoaderSubclass()
        code = loader.source_to_code('')
        self.assertEqual(code.co_filename, '<string>')


(Frozen_ILSourceToCodeTests,
 Source_ILSourceToCodeTests
 ) = test_util.test_both(InspectLoaderSourceToCodeTests,
                         InspectLoaderSubclass=SPLIT_IL)


class InspectLoaderGetCodeTests:

    def test_get_code(self):
        # Test success.
        module = types.ModuleType('blah')
        with mock.patch.object(self.InspectLoaderSubclass, 'get_source') as mocked:
            mocked.return_value = 'attr = 42'
            loader = self.InspectLoaderSubclass()
            code = loader.get_code('blah')
        exec(code, module.__dict__)
        self.assertEqual(module.attr, 42)

    def test_get_code_source_is_None(self):
        # If get_source() is None then this should be None.
        with mock.patch.object(self.InspectLoaderSubclass, 'get_source') as mocked:
            mocked.return_value = None
            loader = self.InspectLoaderSubclass()
            code = loader.get_code('blah')
        self.assertIsNone(code)

    def test_get_code_source_not_found(self):
        # If there is no source then there is no code object.
        loader = self.InspectLoaderSubclass()
        with self.assertRaises(ImportError):
            loader.get_code('blah')


(Frozen_ILGetCodeTests,
 Source_ILGetCodeTests
 ) = test_util.test_both(InspectLoaderGetCodeTests,
                         InspectLoaderSubclass=SPLIT_IL)


##### ExecutionLoader concrete methods #########################################
class ExecutionLoaderGetCodeTests:

    def mock_methods(self, *, get_source=False, get_filename=False):
        source_mock_context, filename_mock_context = None, None
        if get_source:
            source_mock_context = mock.patch.object(self.ExecutionLoaderSubclass,
                                                    'get_source')
        if get_filename:
            filename_mock_context = mock.patch.object(self.ExecutionLoaderSubclass,
                                                      'get_filename')
        return source_mock_context, filename_mock_context

    def test_get_code(self):
        path = 'blah.py'
        source_mock_context, filename_mock_context = self.mock_methods(
                get_source=True, get_filename=True)
        with source_mock_context as source_mock, filename_mock_context as name_mock:
            source_mock.return_value = 'attr = 42'
            name_mock.return_value = path
            loader = self.ExecutionLoaderSubclass()
            code = loader.get_code('blah')
        self.assertEqual(code.co_filename, path)
        module = types.ModuleType('blah')
        exec(code, module.__dict__)
        self.assertEqual(module.attr, 42)

    def test_get_code_source_is_None(self):
        # If get_source() is None then this should be None.
        source_mock_context, _ = self.mock_methods(get_source=True)
        with source_mock_context as mocked:
            mocked.return_value = None
            loader = self.ExecutionLoaderSubclass()
            code = loader.get_code('blah')
        self.assertIsNone(code)

    def test_get_code_source_not_found(self):
        # If there is no source then there is no code object.
        loader = self.ExecutionLoaderSubclass()
        with self.assertRaises(ImportError):
            loader.get_code('blah')

    def test_get_code_no_path(self):
        # If get_filename() raises ImportError then simply skip setting the path
        # on the code object.
        source_mock_context, filename_mock_context = self.mock_methods(
                get_source=True, get_filename=True)
        with source_mock_context as source_mock, filename_mock_context as name_mock:
            source_mock.return_value = 'attr = 42'
            name_mock.side_effect = ImportError
            loader = self.ExecutionLoaderSubclass()
            code = loader.get_code('blah')
        self.assertEqual(code.co_filename, '<string>')
        module = types.ModuleType('blah')
        exec(code, module.__dict__)
        self.assertEqual(module.attr, 42)


(Frozen_ELGetCodeTests,
 Source_ELGetCodeTests
 ) = test_util.test_both(ExecutionLoaderGetCodeTests,
                         ExecutionLoaderSubclass=SPLIT_EL)


##### SourceLoader concrete methods ############################################
class SourceOnlyLoader:

    # Globals that should be defined for all modules.
    source = (b"_ = '::'.join([__name__, __file__, __package__, repr(__loader__)])")

    def __init__(self, path):
        self.path = path

    def get_data(self, path):
        if path != self.path:
            raise IOError
        return self.source

    def get_filename(self, fullname):
        return self.path


SPLIT_SOL = make_abc_subclasses(SourceOnlyLoader, 'SourceLoader')


class SourceLoader(SourceOnlyLoader):

    source_mtime = 1

    def __init__(self, path, magic=None):
        super().__init__(path)
        try:
            self.bytecode_path = self.util.cache_from_source(self.path)
        except NotImplementedError:
            self.bytecode_path = None
        self.source_size = len(self.source)
        if magic is None:
            magic = self.util.MAGIC_NUMBER
        data = bytearray(magic)
        data.extend(self.init._pack_uint32(0))
        data.extend(self.init._pack_uint32(self.source_mtime))
        data.extend(self.init._pack_uint32(self.source_size))
        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 OSError

    def path_stats(self, path):
        if path != self.path:
            raise IOError
        return {'mtime': self.source_mtime, 'size': self.source_size}

    def set_data(self, path, data):
        self.written[path] = bytes(data)
        return path == self.bytecode_path


SPLIT_SL = make_abc_subclasses(SourceLoader, util=util, init=init)


class SourceLoaderTestHarness:

    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])
        try:
            self.cached = self.util.cache_from_source(self.path)
        except NotImplementedError:
            self.cached = None
        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.__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.package)
        self.assertEqual(values[3], repr(self.loader))

    def verify_code(self, code_object):
        module = types.ModuleType(self.name)
        module.__file__ = self.path
        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."""

    def test_get_source(self):
        # Verify the source code is returned as a string.
        # If an OSError 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_OSError(path):
            raise OSError
        self.loader.get_data = raise_OSError
        with self.assertRaises(ImportError) as cm:
            self.loader.get_source(self.name)
        self.assertEqual(cm.exception.name, self.name)

    def test_is_package(self):
        # Properly detect when loading a package.
        self.setUp(is_package=False)
        self.assertFalse(self.loader.is_package(self.name))
        self.setUp(is_package=True)
        self.assertTrue(self.loader.is_package(self.name))
        self.assertFalse(self.loader.is_package(self.name + '.__init__'))

    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_source_to_code(self):
        # Verify the compiled code object.
        code = self.loader.source_to_code(self.loader.source, self.path)
        self.verify_code(code)

    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)


(Frozen_SourceOnlyLoaderTests,
 Source_SourceOnlyLoaderTests
 ) = test_util.test_both(SourceOnlyLoaderTests, util=util,
                         loader_mock=SPLIT_SOL)


@unittest.skipIf(sys.dont_write_bytecode, "sys.dont_write_bytecode is true")
@unittest.skipIf(sys.implementation.cache_tag is None,
                 "sys.implementation.cache_tag is None")
class SourceLoaderBytecodeTests(SourceLoaderTestHarness):

    """Test importlib.abc.SourceLoader's use of bytecode.

    Source-only testing handled by SourceOnlyLoaderTests.

    """

    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(self.util.MAGIC_NUMBER)
            data.extend(self.init._pack_uint32(0))
            data.extend(self.init._pack_uint32(self.loader.source_mtime))
            data.extend(self.init._pack_uint32(self.loader.source_size))
            # Make sure there's > 1 reference to code_object so that the
            # marshaled representation below matches the cached representation
            l = [code_object]
            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(OSError):
            bytecode_path = self.util.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__.mro()[1].set_data
        try:
            del self.loader.__class__.mro()[1].set_data
            code_object = self.loader.get_code(self.name)
            self.verify_code(code_object)
        finally:
            self.loader.__class__.mro()[1].set_data = original_set_data

    def test_set_data_raises_exceptions(self):
        # Raising NotImplementedError or OSError is okay for set_data.
        def raise_exception(exc):
            def closure(*args, **kwargs):
                raise exc
            return closure

        self.setUp(magic=b'0000')
        self.loader.set_data = raise_exception(NotImplementedError)
        code_object = self.loader.get_code(self.name)
        self.verify_code(code_object)


(Frozen_SLBytecodeTests,
 SourceSLBytecodeTests
 ) = test_util.test_both(SourceLoaderBytecodeTests, init=init, util=util,
                         loader_mock=SPLIT_SL)


class SourceLoaderGetSourceTests:

    """Tests for importlib.abc.SourceLoader.get_source()."""

    def test_default_encoding(self):
        # Should have no problems with UTF-8 text.
        name = 'mod'
        mock = self.SourceOnlyLoaderMock('mod.file')
        source = 'x = "ü"'
        mock.source = source.encode('utf-8')
        returned_source = mock.get_source(name)
        self.assertEqual(returned_source, source)

    def test_decoded_source(self):
        # Decoding should work.
        name = 'mod'
        mock = self.SourceOnlyLoaderMock("mod.file")
        source = "# coding: Latin-1\nx='ü'"
        assert source.encode('latin-1') != source.encode('utf-8')
        mock.source = source.encode('latin-1')
        returned_source = mock.get_source(name)
        self.assertEqual(returned_source, source)

    def test_universal_newlines(self):
        # PEP 302 says universal newlines should be used.
        name = 'mod'
        mock = self.SourceOnlyLoaderMock('mod.file')
        source = "x = 42\r\ny = -13\r\n"
        mock.source = source.encode('utf-8')
        expect = io.StringIO(source, newline=None).getvalue()
        self.assertEqual(mock.get_source(name), expect)


(Frozen_SourceOnlyLoaderGetSourceTests,
 Source_SourceOnlyLoaderGetSourceTests
 ) = test_util.test_both(SourceLoaderGetSourceTests,
                         SourceOnlyLoaderMock=SPLIT_SOL)


class SourceLoaderDeprecationWarningsTests(unittest.TestCase):
    """Tests SourceLoader deprecation warnings."""

    def test_deprecated_path_mtime(self):
        from importlib.abc import SourceLoader
        class DummySourceLoader(SourceLoader):
            def get_data(self, path):
                return b''

            def get_filename(self, fullname):
                return 'foo.py'

            def path_stats(self, path):
                return {'mtime': 1}

        loader = DummySourceLoader()

        with self.assertWarnsRegex(
            DeprecationWarning,
            r"SourceLoader\.path_mtime is deprecated in favour of "
            r"SourceLoader\.path_stats\(\)\."
        ):
            loader.path_mtime('foo.py')


if __name__ == '__main__':
    unittest.main()
