Remove engine overwrite in pandas TextFileReader patch (#791)

* remove patching of TextFileReader for pandas for version >= 1.2

Author: satylogin

CHANGES.md

@@ -11,6 +11,8 @@ The released versions correspond to PyPI releases.
   compatible, we cannot exclude that we missed some problems.
 * Under macOS, at test start a symlink `/tmp` to the actual temporary directory is
   now created in the fake filesystem.
+* Patching of parsers for pandas >= 1.2 is removed since pandas now uses Python fs functions
+  internally even when the engine selected is "c".
 
 ### Features
 * added possibility to set a path inaccessible under Windows by using `chown()` with

pyfakefs/patched_packages.py

@@ -17,6 +17,7 @@
 import sys
 
 try:
+    import pandas as pd
     import pandas.io.parsers as parsers
 except ImportError:
     parsers = None
@@ -31,6 +32,14 @@
 except ImportError:
     locks = None
 
+# From pandas v 1.2 onwards the python fs functions are used even when the engine
+# selected is "c". This means that we don't explicitly have to change the engine.
+patch_pandas = parsers is not None and [int(v) for v in pd.__version__.split(".")] < [
+    1,
+    2,
+    0,
+]
+
 
 def get_modules_to_patch():
     modules_to_patch = {}
@@ -43,14 +52,14 @@ def get_modules_to_patch():
 
 def get_classes_to_patch():
     classes_to_patch = {}
-    if parsers is not None:
+    if patch_pandas:
         classes_to_patch["TextFileReader"] = "pandas.io.parsers"
     return classes_to_patch
 
 
 def get_fake_module_classes():
     fake_module_classes = {}
-    if parsers is not None:
+    if patch_pandas:
         fake_module_classes["TextFileReader"] = FakeTextFileReader
     return fake_module_classes
 
@@ -94,7 +103,7 @@ def __getattr__(self, name):
             return getattr(self._xlrd_module, name)
 
 
-if parsers is not None:
+if patch_pandas:
     # we currently need to add fake modules for both the parser module and
     # the contained text reader - maybe this can be simplified