Reset Mutex (Issue 2429)

Makefile

@@ -60,7 +60,7 @@ coverage: clean
 	export LANG=en_GB.utf8
 	pytest -v --random-order --cov-config setup.cfg --cov-report term-missing --cov=mu tests/
 
-tidy: 
+tidy:
 	python make.py tidy
 
 black:

mu/app.py

@@ -297,6 +297,16 @@ def __exit__(self, *args, **kwargs):
         self._shared_memory.unlock()
 
     def acquire(self):
+        #
+        # The attach-detach dance is a shim from
+        # https://stackoverflow.com/questions/42549904/qsharedmemory-is-not-getting-deleted-on-application-crash
+        # If the existing shared memory is not held by any active application
+        # (eg because an appimage has hard-crashed) then it will be released
+        # If the memory is held by an active application it will have no effect
+        #
+        self._shared_memory.attach()
+        self._shared_memory.detach()
+
         if self._shared_memory.attach():
             pid = struct.unpack("q", self._shared_memory.data()[:8])
             raise MutexError("MUTEX: Mu is already running with pid %d" % pid)
@@ -354,7 +364,6 @@ def run():
     logging.info("Platform: {}".format(platform.platform()))
     logging.info("Python path: {}".format(sys.path))
     logging.info("Language code: {}".format(i18n.language_code))
-
     setup_exception_handler()
     check_only_running_once()
 

setup.cfg

@@ -23,6 +23,7 @@ exclude =
     ./.venv*/
     ./env/
     ./.env/
+    ./local-scripts/
 max-line-length = 88
 
 [coverage:run]