More performance improvements

- do not import pytest if not needed - moved SKIPMODULE setting
  back to pytest plugin
- move warning supression out of loop
- slight improvement of temp path creation performance

Author: mrbean-bremen

CHANGES.md

@@ -3,7 +3,6 @@ The released versions correspond to PyPi releases.
 
 ## Version 4.3.0 (as yet unreleased)
 
-
 ### Changes
   * The `patchfs` decorator now expects a positional argument instead of the
     keyword arguments `fs`. This avoids confusion with the pytest `fs`
@@ -14,6 +13,7 @@ The released versions correspond to PyPi releases.
     default to avoid a large performance impact. An additional parameter
     `patch_default_args` has been added that switches this behavior on
     (see [#567](../../issues/567)).
+  * Some setup performance improvements have been added  
 
 ## [Version 4.2.1](https://pypi.python.org/pypi/pyfakefs/4.2.1) (2020-11-02)
 

pyfakefs/fake_filesystem.py

@@ -1014,6 +1014,17 @@ def _starts_with_sep(self, path):
         return (path.startswith(sep) or altsep is not None and
                 path.startswith(altsep))
 
+    def _add_c_drive(self):
+        """Optimized version for the default Windows C drive.
+        For internal use only.
+        """
+        if self.is_windows_fs:
+            self.last_dev += 1
+            self.mount_points['C:'] = {
+                'idev': self.last_dev, 'total_size': None, 'used_size': 0
+            }
+            self.root.get_entry('C:') .st_dev = self.last_dev
+
     def add_mount_point(self, path, total_size=None):
         """Add a new mount point for a filesystem device.
         The mount point gets a new unique device number.
@@ -2306,14 +2317,15 @@ def make_string_path(self, path):
         fake_sep = matching_string(path, self.path_separator)
         return path.replace(os_sep, fake_sep)
 
-    def create_dir(self, directory_path, perm_bits=PERM_DEF):
+    def create_dir(self, directory_path, perm_bits=PERM_DEF, check=True):
         """Create `directory_path`, and all the parent directories.
 
         Helper method to set up your test faster.
 
         Args:
             directory_path: The full directory path to create.
             perm_bits: The permission bits as set by `chmod`.
+            check: For internal use only.
 
         Returns:
             The newly created FakeDirectory object.
@@ -2322,10 +2334,11 @@ def create_dir(self, directory_path, perm_bits=PERM_DEF):
             OSError: if the directory already exists.
         """
         directory_path = self.make_string_path(directory_path)
-        directory_path = self.absnormpath(directory_path)
-        self._auto_mount_drive_if_needed(directory_path)
-        if self.exists(directory_path, check_link=True):
-            self.raise_os_error(errno.EEXIST, directory_path)
+        if check:
+            directory_path = self.absnormpath(directory_path)
+            self._auto_mount_drive_if_needed(directory_path)
+            if self.exists(directory_path, check_link=True):
+                self.raise_os_error(errno.EEXIST, directory_path)
         path_components = self._path_components(directory_path)
         current_dir = self.root
 
@@ -2338,10 +2351,10 @@ def create_dir(self, directory_path, perm_bits=PERM_DEF):
                 current_dir.add_entry(new_dir)
                 current_dir = new_dir
             else:
-                if S_ISLNK(directory.st_mode):
+                if check and S_ISLNK(directory.st_mode):
                     directory = self.resolve(directory.contents)
                 current_dir = directory
-                if directory.st_mode & S_IFDIR != S_IFDIR:
+                if check and directory.st_mode & S_IFDIR != S_IFDIR:
                     self.raise_os_error(errno.ENOTDIR, current_dir.path)
 
         # set the permission after creating the directories

pyfakefs/fake_filesystem_unittest.py

@@ -362,13 +362,6 @@ class Patcher:
         None, fake_filesystem, fake_filesystem_shutil,
         sys, linecache, tokenize
     }
-    try:
-        import py
-        import pytest
-        SKIPMODULES.add(py)
-        SKIPMODULES.add(pytest)
-    except ImportError:
-        pass
 
     assert None in SKIPMODULES, ("sys.modules contains 'None' values;"
                                  " must skip them.")
@@ -606,7 +599,6 @@ def _find_modules(self):
         Later, `setUp()` will stub these with the fake file system
         modules.
         """
-
         module_names = list(self._fake_module_classes.keys()) + [PATH_MODULE]
         for name, module in list(sys.modules.items()):
             try:
@@ -622,33 +614,27 @@ def _find_modules(self):
                             for sn in self._skip_names]))
             module_items = module.__dict__.copy().items()
 
-            with warnings.catch_warnings():
-                # ignore deprecation warnings, see #542
-                warnings.filterwarnings(
-                    'ignore',
-                    category=DeprecationWarning
-                )
-                modules = {name: mod for name, mod in module_items
-                           if self._is_fs_module(mod, name, module_names)}
-
-                if skipped:
-                    for name, mod in modules.items():
-                        self._skipped_modules.setdefault(name, set()).add(
-                            (module, mod.__name__))
-                    continue
+            modules = {name: mod for name, mod in module_items
+                       if self._is_fs_module(mod, name, module_names)}
 
+            if skipped:
                 for name, mod in modules.items():
-                    self._modules.setdefault(name, set()).add(
+                    self._skipped_modules.setdefault(name, set()).add(
                         (module, mod.__name__))
-                functions = {name: fct for name, fct in
-                             module_items
-                             if self._is_fs_function(fct)}
+                continue
+
+            for name, mod in modules.items():
+                self._modules.setdefault(name, set()).add(
+                    (module, mod.__name__))
+            functions = {name: fct for name, fct in
+                         module_items
+                         if self._is_fs_function(fct)}
 
-                # find default arguments that are file system functions
-                if self.patch_default_args:
-                    for _, fct in module_items:
-                        for f, i, d in self._def_values(fct):
-                            self._def_functions.append((f, i, d))
+            # find default arguments that are file system functions
+            if self.patch_default_args:
+                for _, fct in module_items:
+                    for f, i, d in self._def_values(fct):
+                        self._def_functions.append((f, i, d))
 
             for name, fct in functions.items():
                 self._fct_modules.setdefault(
@@ -684,7 +670,13 @@ def setUp(self, doctester=None):
             shutil._HAS_FCOPYFILE = False
 
         temp_dir = tempfile.gettempdir()
-        self._find_modules()
+        with warnings.catch_warnings():
+            # ignore deprecation warnings, see #542
+            warnings.filterwarnings(
+                'ignore',
+                category=DeprecationWarning
+            )
+            self._find_modules()
         self._refresh()
 
         if doctester is not None:
@@ -696,7 +688,8 @@ def setUp(self, doctester=None):
 
         # the temp directory is assumed to exist at least in `tempfile1`,
         # so we create it here for convenience
-        self.fs.create_dir(temp_dir)
+        self.fs.create_dir(temp_dir, check=False)
+        self.fs._add_c_drive()
 
     def start_patching(self):
         if not self._patching:

pyfakefs/pytest_plugin.py

@@ -9,10 +9,14 @@ def my_fakefs_test(fs):
     assert os.path.exists('/var/data/xx1.txt')
 """
 
+import py
 import pytest
 
 from pyfakefs.fake_filesystem_unittest import Patcher
 
+Patcher.SKIPMODULES.add(py)
+Patcher.SKIPMODULES.add(pytest)
+
 
 @pytest.fixture
 def fs(request):