Fix newly introduced support for opener argument in open

CHANGES.md

@@ -3,6 +3,10 @@ The released versions correspond to PyPi releases.
 
 ## Unreleased
 
+### Fixes
+* fixed support for `opener` introduced in previous patch release 
+  (see [#689](../../issues/689))
+
 ## [Version 4.6.1](https://pypi.python.org/pypi/pyfakefs/4.6.1) (2022-07-13)
 Fixes incompatibility with Python 3.11 beta 4.
 

pyfakefs/fake_filesystem.py

@@ -5746,7 +5746,7 @@ def call(self, file_: Union[AnyStr, int],
         if opener is not None:
             # opener shall return a file descriptor, which will be handled
             # here as if directly passed
-            file_ = opener(file_, open_modes)
+            file_ = opener(file_, self._open_flags_from_open_modes(open_modes))
 
         file_object, file_path, filedes, real_path = self._handle_file_arg(
             file_)
@@ -5770,7 +5770,7 @@ def call(self, file_: Union[AnyStr, int],
         if not filedes:
             closefd = True
 
-        if (open_modes.must_not_exist and
+        if (not opener and open_modes.must_not_exist and
                 (file_object or self.filesystem.islink(file_path) and
                  not self.filesystem.is_windows_fs)):
             self.filesystem.raise_os_error(errno.EEXIST, file_path)
@@ -5819,6 +5819,26 @@ def call(self, file_: Union[AnyStr, int],
             fakefile.filedes = self.filesystem._add_open_file(fakefile)
         return fakefile
 
+    @staticmethod
+    def _open_flags_from_open_modes(open_modes: _OpenModes) -> int:
+        flags = 0
+        if open_modes.can_read and open_modes.can_write:
+            flags |= os.O_RDWR
+        elif open_modes.can_read:
+            flags |= os.O_RDONLY
+        elif open_modes.can_write:
+            flags |= os.O_WRONLY
+
+        if open_modes.append:
+            flags |= os.O_APPEND
+        if open_modes.truncate:
+            flags |= os.O_TRUNC
+        if not open_modes.must_exist and open_modes.can_write:
+            flags |= os.O_CREAT
+        if open_modes.must_not_exist and open_modes.can_write:
+            flags |= os.O_EXCL
+        return flags
+
     def _init_file_object(self, file_object: Optional[FakeFile],
                           file_path: AnyStr,
                           open_modes: _OpenModes,

pyfakefs/tests/fake_open_test.py

@@ -949,6 +949,98 @@ def use_real_fs(self):
         return True
 
 
+class FakeFileOpenWithOpenerTest(FakeFileOpenTestBase):
+    def opener(self, path, flags):
+        return self.os.open(path, flags)
+
+    def test_use_opener_with_read(self):
+        file_path = self.make_path('foo')
+        self.create_file(file_path, contents='test')
+        with self.open(file_path, opener=self.opener) as f:
+            assert f.read() == 'test'
+            with self.assertRaises(OSError):
+                f.write('foo')
+
+    def test_use_opener_with_read_plus(self):
+        file_path = self.make_path('foo')
+        self.create_file(file_path, contents='test')
+        with self.open(file_path, 'r+', opener=self.opener) as f:
+            assert f.read() == 'test'
+            assert f.write('bar') == 3
+        with self.open(file_path) as f:
+            assert f.read() == 'testbar'
+
+    def test_use_opener_with_write(self):
+        file_path = self.make_path('foo')
+        self.create_file(file_path, contents='foo')
+        with self.open(file_path, 'w', opener=self.opener) as f:
+            with self.assertRaises(OSError):
+                f.read()
+            assert f.write('bar') == 3
+        with self.open(file_path) as f:
+            assert f.read() == 'bar'
+
+    def test_use_opener_with_write_plus(self):
+        file_path = self.make_path('foo')
+        self.create_file(file_path, contents='test')
+        with self.open(file_path, 'w+', opener=self.opener) as f:
+            assert f.read() == ''
+            assert f.write('bar') == 3
+        with self.open(file_path) as f:
+            assert f.read() == 'bar'
+
+    def test_use_opener_with_append(self):
+        file_path = self.make_path('foo')
+        self.create_file(file_path, contents='foo')
+        with self.open(file_path, 'a', opener=self.opener) as f:
+            assert f.write('bar') == 3
+            with self.assertRaises(OSError):
+                f.read()
+        with self.open(file_path) as f:
+            assert f.read() == 'foobar'
+
+    def test_use_opener_with_append_plus(self):
+        file_path = self.make_path('foo')
+        self.create_file(file_path, contents='foo')
+        with self.open(file_path, 'a+', opener=self.opener) as f:
+            assert f.read() == ''
+            assert f.write('bar') == 3
+        with self.open(file_path) as f:
+            assert f.read() == 'foobar'
+
+    def test_use_opener_with_exclusive_write(self):
+        file_path = self.make_path('foo')
+        self.create_file(file_path, contents='test')
+        with self.assertRaises(OSError):
+            self.open(file_path, 'x', opener=self.opener)
+
+        file_path = self.make_path('bar')
+        with self.open(file_path, 'x', opener=self.opener) as f:
+            assert f.write('bar') == 3
+            with self.assertRaises(OSError):
+                f.read()
+        with self.open(file_path) as f:
+            assert f.read() == 'bar'
+
+    def test_use_opener_with_exclusive_plus(self):
+        file_path = self.make_path('foo')
+        self.create_file(file_path, contents='test')
+        with self.assertRaises(OSError):
+            self.open(file_path, 'x+', opener=self.opener)
+
+        file_path = self.make_path('bar')
+        with self.open(file_path, 'x+', opener=self.opener) as f:
+            assert f.write('bar') == 3
+            assert f.read() == ''
+        with self.open(file_path) as f:
+            assert f.read() == 'bar'
+
+
+class RealFileOpenWithOpenerTest(FakeFileOpenWithOpenerTest):
+    def use_real_fs(self):
+        return True
+
+
 @unittest.skipIf(sys.version_info < (3, 8),
                  'open_code only present since Python 3.8')
 class FakeFilePatchedOpenCodeTest(FakeFileOpenTestBase):