Make portalocker optional

.github/workflows/python-package.yml

@@ -16,7 +16,7 @@ jobs:
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        python-version: [3.7, 3.8, 3.9, 2.7]
+        python-version: [3.7, 3.8, 3.9, "3.10"]
         os: [ubuntu-latest, windows-latest, macos-latest]
         include:
           # https://docs.github.com/en/actions/reference/workflow-syntax-for-github-actions#using-environment-variables-in-a-matrix
@@ -26,8 +26,8 @@ jobs:
             toxenv: "py38"
           - python-version: 3.9
             toxenv: "py39"
-          - python-version: 2.7
-            toxenv: "py27"
+          - python-version: "3.10"
+            toxenv: "py310"
           - python-version: 3.9
             os: ubuntu-latest
             lint: "true"

msal_extensions/__init__.py

@@ -8,6 +8,9 @@
     KeychainPersistence,
     LibsecretPersistence,
     )
-from .cache_lock import CrossPlatLock
+try:
+    from .cache_lock import CrossPlatLock, LockError  # It needs portalocker
+except ImportError:
+    from .filelock import CrossPlatLock, LockError
 from .token_cache import PersistedTokenCache
 

msal_extensions/cache_lock.py

@@ -6,12 +6,15 @@
 import logging
 from distutils.version import LooseVersion
 
-import portalocker
+import portalocker  # pylint: disable=import-error
 
 
 logger = logging.getLogger(__name__)
 
 
+LockError = portalocker.exceptions.LockException
+
+
 class CrossPlatLock(object):
     """Offers a mechanism for waiting until another process is finished interacting with a shared
     resource. This is specifically written to interact with a class of the same name in the .NET

msal_extensions/filelock.py

@@ -0,0 +1,62 @@
+"""A cross-process lock based on exclusive creation of a given file name"""
+import os
+import sys
+import errno
+import time
+import logging
+
+
+logger = logging.getLogger(__name__)
+
+
+class LockError(RuntimeError):
+    """It will be raised when unable to obtain a lock"""
+
+
+class CrossPlatLock(object):
+    """This implementation relies only on ``open(..., 'x')``"""
+    def __init__(self, lockfile_path):
+        self._lockpath = lockfile_path
+
+    def __enter__(self):
+        self._create_lock_file('{} {}'.format(
+            os.getpid(),
+            sys.argv[0],
+            ).encode('utf-8'))  # pylint: disable=consider-using-f-string
+        return self
+
+    def _create_lock_file(self, content):
+        timeout = 5
+        check_interval = 0.25
+        current_time = getattr(time, "monotonic", time.time)
+        timeout_end = current_time() + timeout
+        while timeout_end > current_time():
+            try:
+                with open(self._lockpath, 'xb') as lock_file:  # pylint: disable=unspecified-encoding
+                    lock_file.write(content)
+                return None  # Happy path
+            except ValueError:  # This needs to be the first clause, for Python 2 to hit it
+                raise LockError("Python 2 does not support atomic creation of file")
+            except FileExistsError:  # Only Python 3 will reach this clause
+                logger.debug(
+                    "Process %d found existing lock file, will retry after %f second",
+                    os.getpid(), check_interval)
+                time.sleep(check_interval)
+        raise LockError(
+            "Unable to obtain lock, despite trying for {} second(s). "
+            "You may want to manually remove the stale lock file {}".format(
+                timeout,
+                self._lockpath,
+            ))
+
+    def __exit__(self, *args):
+        try:
+            os.remove(self._lockpath)
+        except OSError as ex:  # pylint: disable=invalid-name
+            if ex.errno in (errno.ENOENT, errno.EACCES):
+                # Probably another process has raced this one
+                # and ended up clearing or locking the file for itself.
+                logger.debug("Unable to remove lock file")
+            else:
+                raise
+

msal_extensions/token_cache.py

@@ -5,7 +5,10 @@
 
 import msal
 
-from .cache_lock import CrossPlatLock
+try:
+    from .cache_lock import CrossPlatLock  # It needs portalocker
+except ImportError:
+    from .filelock import CrossPlatLock
 from .persistence import _mkdir_p, PersistenceNotFound
 
 

setup.py

@@ -22,7 +22,12 @@
     package_data={'': ['LICENSE']},
     install_requires=[
         'msal>=0.4.1,<2.0.0',
-
+        "pathlib2;python_version<'3.0'",
+        ## We choose to NOT define a hard dependency on this.
+        # "pygobject>=3,<4;platform_system=='Linux'",
+    ],
+    extras_require={
+        "portalocker": [
         # In order to implement these requirements:
         #       Lowerbound = (1.6 if playform_system == 'Windows' else 1.0)
         #       Upperbound < (3 if python_version >= '3.5' else 2)
@@ -32,10 +37,7 @@
         "portalocker<2,>=1.0;python_version=='2.7' and platform_system!='Windows'",
         "portalocker<3,>=1.6;python_version>='3.5' and platform_system=='Windows'",
         "portalocker<2,>=1.6;python_version=='2.7' and platform_system=='Windows'",
-
-        "pathlib2;python_version<'3.0'",
-        ## We choose to NOT define a hard dependency on this.
-        # "pygobject>=3,<4;platform_system=='Linux'",
-    ],
+        ],
+    },
     tests_require=['pytest'],
 )

tests/cache_file_generator.py

@@ -14,9 +14,10 @@
 import sys
 import time
 
-from portalocker import exceptions
+from msal_extensions import FilePersistence, CrossPlatLock, LockError
 
-from msal_extensions import FilePersistence, CrossPlatLock
+
+print("Testing with {}".format(CrossPlatLock))
 
 
 def _acquire_lock_and_write_to_cache(cache_location, sleep_interval):
@@ -31,7 +32,7 @@ def _acquire_lock_and_write_to_cache(cache_location, sleep_interval):
             time.sleep(sleep_interval)
             data += "> " + str(os.getpid()) + "\n"
             cache_accessor.save(data)
-    except exceptions.LockException as e:
+    except LockError as e:
         logging.warning("Unable to acquire lock %s", e)
 
 

tests/test_crossplatlock.py

@@ -1,5 +1,5 @@
 import pytest
-from msal_extensions.cache_lock import CrossPlatLock
+from msal_extensions import CrossPlatLock
 
 
 def test_ensure_file_deleted():
@@ -10,6 +10,7 @@ def test_ensure_file_deleted():
     except NameError:
         FileNotFoundError = IOError
 
+    print("Testing with {}".format(CrossPlatLock))
     with CrossPlatLock(lockfile):
         pass
 

tox.ini

@@ -1,5 +1,5 @@
 [tox]
-envlist = py27,py35,py36,py37,py38
+envlist = py35,py36,py37,py38,py39,py310
 
 [testenv]
 deps = pytest