Added methods to access real files

CHANGES.md

@@ -4,7 +4,11 @@ The release versions are PyPi releases.
 ## Version 3.2 (as yet unreleased)
 
 #### New Features
- * Added the CHANGES.md release notes to the release manifest
+  * Added new methods to `fake_filesystem.FakeFilesystem` that make real files 
+    and directories appear within the fake file system: 
+    `add_real_file()`, `add_real_directory()` and `add_real_paths()`.
+    File contents are read from the real file system only when needed.
+  * Added the CHANGES.md release notes to the release manifest
 
 #### Fixes
  * `pathlib.glob()` incorrectly handled case under MacOS (#167)

example.py

@@ -132,5 +132,10 @@ def rm_tree(path):
     shutil.rmtree(path)
 
 def scandir(path):
-    """Returns a list of directory entries for the given path."""
+    """Return a list of directory entries for the given path."""
     return list(os.scandir(path))
+
+def file_contents(path):
+    """Return the contents of the given path as byte array."""
+    with open(path, 'rb') as f:
+        return f.read()

example_test.py

@@ -30,6 +30,8 @@
 import os
 import sys
 
+from pyfakefs.fake_filesystem_unittest import REAL_OPEN
+
 if sys.version_info < (2, 7):
     import unittest2 as unittest
 else:
@@ -135,13 +137,22 @@ def test_scandir(self):
         self.fs.CreateFile('/linktest/linked')
         self.fs.CreateLink('/test/linked_file', '/linktest/linked')
 
-        entries = sorted(os.scandir('/test'), key=lambda e: e.name)
+        entries = sorted(example.scandir('/test'), key=lambda e: e.name)
         self.assertEqual(3, len(entries))
         self.assertEqual('linked_file', entries[1].name)
         self.assertTrue(entries[0].is_dir())
         self.assertTrue(entries[1].is_symlink())
         self.assertTrue(entries[2].is_file())
 
+    def test_real_file_access(self):
+        """Test `example.file_contents()` for a real file after adding it using `add_real_file()`."""
+        real_file = __file__
+        with REAL_OPEN(real_file, 'rb') as f:
+            real_contents = f.read()
+        self.assertRaises(IOError, example.file_contents, real_file)
+        self.fs.add_real_file(real_file)
+        self.assertEqual(example.file_contents(real_file), real_contents)
+
 
 if __name__ == "__main__":
     unittest.main()

fake_filesystem_test.py

@@ -4186,6 +4186,7 @@ def testDiskUsageOnFileCreation(self):
 
         total_size = 100
         self.filesystem.AddMountPoint('mount', total_size)
+
         def create_too_large_file():
             with fake_open('!mount!file', 'w') as dest:
                 dest.write('a' * (total_size + 1))
@@ -4199,7 +4200,6 @@ def create_too_large_file():
 
         self.assertEqual(total_size, self.filesystem.GetDiskUsage('!mount').used)
 
-
     def testFileSystemSizeAfterLargeFileCreation(self):
         filesystem = fake_filesystem.FakeFilesystem(path_separator='!',
                                                     total_size=1024 * 1024 * 1024 * 100)
@@ -4444,5 +4444,136 @@ def testThatUncPathsAreAutoMounted(self):
         self.assertEqual(5, self.filesystem.GetObject('!!foo!bar!bip!bop').st_dev)
 
 
+class RealFileSystemAccessTest(TestCase):
+    def setUp(self):
+        # use the real path separator to work with the real file system
+        self.filesystem = fake_filesystem.FakeFilesystem()
+        self.fake_open = fake_filesystem.FakeFileOpen(self.filesystem)
+
+    def testAddNonExistingRealFileRaises(self):
+        nonexisting_path = os.path.join('nonexisting', 'test.txt')
+        self.assertRaises(OSError, self.filesystem.add_real_file, nonexisting_path)
+        self.assertFalse(self.filesystem.Exists(nonexisting_path))
+
+    def testAddNonExistingRealDirectoryRaises(self):
+        nonexisting_path = '/nonexisting'
+        self.assertRaisesIOError(errno.ENOENT, self.filesystem.add_real_directory, nonexisting_path)
+        self.assertFalse(self.filesystem.Exists(nonexisting_path))
+
+    def testExistingFakeFileRaises(self):
+        real_file_path = __file__
+        self.filesystem.CreateFile(real_file_path)
+        self.assertRaisesIOError(errno.EEXIST, self.filesystem.add_real_file, real_file_path)
+
+    def testExistingFakeDirectoryRaises(self):
+        real_dir_path = os.path.dirname(__file__)
+        self.filesystem.CreateDirectory(real_dir_path)
+        self.assertRaisesOSError(errno.EEXIST, self.filesystem.add_real_directory, real_dir_path)
+
+    def checkFakeFileStat(self, fake_file, real_file_path):
+        self.assertTrue(self.filesystem.Exists(real_file_path))
+        real_stat = os.stat(real_file_path)
+        self.assertIsNone(fake_file._byte_contents)
+        self.assertEqual(fake_file.st_size, real_stat.st_size)
+        self.assertEqual(fake_file.st_ctime, real_stat.st_ctime)
+        self.assertEqual(fake_file.st_atime, real_stat.st_atime)
+        self.assertEqual(fake_file.st_mtime, real_stat.st_mtime)
+        self.assertEqual(fake_file.st_uid, real_stat.st_uid)
+        self.assertEqual(fake_file.st_gid, real_stat.st_gid)
+
+    def checkReadOnlyFile(self, fake_file, real_file_path):
+        with open(real_file_path, 'rb') as f:
+            real_contents = f.read()
+        self.assertEqual(fake_file.byte_contents, real_contents)
+        self.assertRaisesIOError(errno.EACCES, self.fake_open, real_file_path, 'w')
+
+    def checkWritableFile(self, fake_file, real_file_path):
+        with open(real_file_path, 'rb') as f:
+            real_contents = f.read()
+        self.assertEqual(fake_file.byte_contents, real_contents)
+        with self.fake_open(real_file_path, 'wb') as f:
+            f.write(b'test')
+        with open(real_file_path, 'rb') as f:
+            real_contents1 = f.read()
+        self.assertEqual(real_contents1, real_contents)
+        with self.fake_open(real_file_path, 'rb') as f:
+            fake_contents = f.read()
+        self.assertEqual(fake_contents, b'test')
+
+    def testAddExistingRealFileReadOnly(self):
+        real_file_path = __file__
+        fake_file = self.filesystem.add_real_file(real_file_path)
+        self.checkFakeFileStat(fake_file, real_file_path)
+        self.assertEqual(fake_file.st_mode & 0o333, 0)
+        self.checkReadOnlyFile(fake_file, real_file_path)
+
+    def testAddExistingRealFileReadWrite(self):
+        real_file_path = os.path.realpath(__file__)
+        fake_file = self.filesystem.add_real_file(real_file_path, read_only=False)
+
+        self.checkFakeFileStat(fake_file, real_file_path)
+        self.assertEqual(fake_file.st_mode, os.stat(real_file_path).st_mode)
+        self.checkWritableFile(fake_file, real_file_path)
+
+    def testAddExistingRealDirectoryReadOnly(self):
+        real_dir_path = os.path.join(os.path.dirname(__file__), 'pyfakefs')
+        fake_dir = self.filesystem.add_real_directory(real_dir_path)
+        self.assertTrue(self.filesystem.Exists(real_dir_path))
+        self.assertTrue(self.filesystem.Exists(os.path.join(real_dir_path, 'fake_filesystem.py')))
+        self.assertTrue(self.filesystem.Exists(os.path.join(real_dir_path, 'fake_pathlib.py')))
+
+        file_path = os.path.join(real_dir_path, 'fake_tempfile.py')
+        fake_file = self.filesystem.ResolveObject(file_path)
+        self.checkFakeFileStat(fake_file, file_path)
+        self.checkReadOnlyFile(fake_file, file_path)
+
+    def testAddExistingRealDirectoryTree(self):
+        real_dir_path = os.path.dirname(__file__)
+        self.filesystem.add_real_directory(real_dir_path)
+        self.assertTrue(self.filesystem.Exists(os.path.join(real_dir_path, 'fake_filesystem_test.py')))
+        self.assertTrue(self.filesystem.Exists(os.path.join(real_dir_path, 'pyfakefs', 'fake_filesystem.py')))
+        self.assertTrue(self.filesystem.Exists(os.path.join(real_dir_path, 'pyfakefs', '__init__.py')))
+
+    def testAddExistingRealDirectoryReadWrite(self):
+        real_dir_path = os.path.join(os.path.dirname(__file__), 'pyfakefs')
+        self.filesystem.add_real_directory(real_dir_path, read_only=False)
+        self.assertTrue(self.filesystem.Exists(real_dir_path))
+        self.assertTrue(self.filesystem.Exists(os.path.join(real_dir_path, 'fake_filesystem.py')))
+        self.assertTrue(self.filesystem.Exists(os.path.join(real_dir_path, 'fake_pathlib.py')))
+
+        file_path = os.path.join(real_dir_path, 'pytest_plugin.py')
+        fake_file = self.filesystem.ResolveObject(file_path)
+        self.checkFakeFileStat(fake_file, file_path)
+        self.checkWritableFile(fake_file, file_path)
+
+    def testAddExistingRealPathsReadOnly(self):
+        real_file_path = os.path.realpath(__file__)
+        real_dir_path = os.path.join(os.path.dirname(__file__), 'pyfakefs')
+        self.filesystem.add_real_paths([real_file_path, real_dir_path])
+
+        fake_file = self.filesystem.ResolveObject(real_file_path)
+        self.checkFakeFileStat(fake_file, real_file_path)
+        self.checkReadOnlyFile(fake_file, real_file_path)
+
+        real_file_path = os.path.join(real_dir_path, 'fake_filesystem_shutil.py')
+        fake_file = self.filesystem.ResolveObject(real_file_path)
+        self.checkFakeFileStat(fake_file, real_file_path)
+        self.checkReadOnlyFile(fake_file, real_file_path)
+
+    def testAddExistingRealPathsReadWrite(self):
+        real_file_path = os.path.realpath(__file__)
+        real_dir_path = os.path.join(os.path.dirname(__file__), 'pyfakefs')
+        self.filesystem.add_real_paths([real_file_path, real_dir_path], read_only=False)
+
+        fake_file = self.filesystem.ResolveObject(real_file_path)
+        self.checkFakeFileStat(fake_file, real_file_path)
+        self.checkWritableFile(fake_file, real_file_path)
+
+        real_file_path = os.path.join(real_dir_path, 'fake_filesystem_glob.py')
+        fake_file = self.filesystem.ResolveObject(real_file_path)
+        self.checkFakeFileStat(fake_file, real_file_path)
+        self.checkWritableFile(fake_file, real_file_path)
+
+
 if __name__ == '__main__':
     unittest.main()

fake_filesystem_unittest_test.py

@@ -190,7 +190,7 @@ def test_own_path_module(self):
 
 
 @unittest.skipIf(sys.version_info < (2, 7), "No byte strings in Python 2.6")
-class TestCopyRealFile(TestPyfakefsUnittestBase):
+class TestCopyOrAddRealFile(TestPyfakefsUnittestBase):
     """Tests the `fake_filesystem_unittest.TestCase.copyRealFile()` method."""
     with open(__file__) as f:
         real_string_contents = f.read()
@@ -235,6 +235,28 @@ def testCopyRealFileNoDestination(self):
         self.copyRealFile(real_file_path)
         self.assertTrue(self.fs.Exists(real_file_path))
 
+    def testAddRealFile(self):
+        '''Add a real file to the fake file system to be read on demand'''
+
+        # this tests only the basic functionality inside a unit test, more thorough tests
+        # are done in fake_filesystem_test.RealFileSystemAccessTest
+        real_file_path = __file__
+        fake_file = self.fs.add_real_file(real_file_path)
+        self.assertTrue(self.fs.Exists(real_file_path))
+        self.assertIsNone(fake_file._byte_contents)
+        self.assertEqual(self.real_byte_contents, fake_file.byte_contents)
+
+    def testAddRealDirectory(self):
+        '''Add a real directory and the contained files to the fake file system to be read on demand'''
+
+        # this tests only the basic functionality inside a unit test, more thorough tests
+        # are done in fake_filesystem_test.RealFileSystemAccessTest
+        # Note: this test fails (add_real_directory raises) if 'genericpath' is not added to SKIPNAMES
+        real_dir_path = os.path.join(os.path.dirname(__file__), 'pyfakefs')
+        self.fs.add_real_directory(real_dir_path)
+        self.assertTrue(self.fs.Exists(real_dir_path))
+        self.assertTrue(self.fs.Exists(os.path.join(real_dir_path, 'fake_filesystem.py')))
+
 
 if __name__ == "__main__":
     unittest.main()